1、前提介绍：

关于Android 手势识别就是当前view 根据用户的不同touch行为，给出不同的处理结果。这里我介绍一下我自己做的一些手势识别如下。
在这里插入图片描述

2、单指相关

2.1 单指点击、长按、拖动、左滑、右滑、上滑、下滑，在frameworks/base/core/java/android/view/GestureDetector.java Android原生代码就已经实现了。我们使用的时候只需要继承 SimpleOnGestureListener class，然后通过调用 new GestureDetector(context, new SimpleGesture(), null, true /* ignoreMultitouch */); 的时候将继承自 SimpleOnGestureListener 的class 作为参数传递给GestureDetector就可以了。

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.view;

import android.content.Context;
import android.os.Handler;
import android.os.Message;

/**
 * Detects various gestures and events using the supplied {@link MotionEvent}s.
 * The {@link OnGestureListener} callback will notify users when a particular
 * motion event has occurred. This class should only be used with {@link MotionEvent}s
 * reported via touch (don't use for trackball events).
 *
 * To use this class:
 * <ul>
 *  <li>Create an instance of the {@code GestureDetector} for your {@link View}
 *  <li>In the {@link View#onTouchEvent(MotionEvent)} method ensure you call
 *          {@link #onTouchEvent(MotionEvent)}. The methods defined in your callback
 *          will be executed when the events occur.
 *  <li>If listening for {@link OnContextClickListener#onContextClick(MotionEvent)}
 *          you must call {@link #onGenericMotionEvent(MotionEvent)}
 *          in {@link View#onGenericMotionEvent(MotionEvent)}.
 * </ul>
 */
public class GestureDetector {
    /**
     * The listener that is used to notify when gestures occur.
     * If you want to listen for all the different gestures then implement
     * this interface. If you only want to listen for a subset it might
     * be easier to extend {@link SimpleOnGestureListener}.
     */
    public interface OnGestureListener {

        /**
         * Notified when a tap occurs with the down {@link MotionEvent}
         * that triggered it. This will be triggered immediately for
         * every down event. All other events should be preceded by this.
         *
         * @param e The down motion event.
         */
        boolean onDown(MotionEvent e);   // 接收down事件

        /**
         * The user has performed a down {@link MotionEvent} and not performed
         * a move or up yet. This event is commonly used to provide visual
         * feedback to the user to let them know that their action has been
         * recognized i.e. highlight an element.
         *
         * @param e The down motion event
         */
        void onShowPress(MotionEvent e); 

        /**
         * Notified when a tap occurs with the up {@link MotionEvent}
         * that triggered it.
         *
         * @param e The up motion event that completed the first tap
         * @return true if the event is consumed, else false
         */
        boolean onSingleTapUp(MotionEvent e);

        /**
         * Notified when a scroll occurs with the initial on down {@link MotionEvent} and the
         * current move {@link MotionEvent}. The distance in x and y is also supplied for
         * convenience.
         *
         * @param e1 The first down motion event that started the scrolling.
         * @param e2 The move motion event that triggered the current onScroll.
         * @param distanceX The distance along the X axis that has been scrolled since the last
         *              call to onScroll. This is NOT the distance between {@code e1}
         *              and {@code e2}.
         * @param distanceY The distance along the Y axis that has been scrolled since the last
         *              call to onScroll. This is NOT the distance between {@code e1}
         *              and {@code e2}.
         * @return true if the event is consumed, else false
         */
        boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);//通过这个方法可以监听拖动事件

        /**
         * Notified when a long press occurs with the initial on down {@link MotionEvent}
         * that trigged it.
         *
         * @param e The initial on down motion event that started the longpress.
         */
        void onLongPress(MotionEvent e); // 通过这个方法可以监听长按事件，长按的时间可以通过Android提供的接口来设定

        /**
         * Notified of a fling event when it occurs with the initial on down {@link MotionEvent}
         * and the matching up {@link MotionEvent}. The calculated velocity is supplied along
         * the x and y axis in pixels per second.
         *
         * @param e1 The first down motion event that started the fling.
         * @param e2 The move motion event that triggered the current onFling.
         * @param velocityX The velocity of this fling measured in pixels per second
         *              along the x axis.
         * @param velocityY The velocity of this fling measured in pixels per second
         *              along the y axis.
         * @return true if the event is consumed, else false
         */
        boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY); // 通过这个方法判断滑动，上面的onScroll是提供实时的，这个onFling是判断滑动结果的。
    }

    /**
     * The listener that is used to notify when a double-tap or a confirmed
     * single-tap occur.
     */
    public interface OnDoubleTapListener {
        /**
         * Notified when a single-tap occurs.
         * <p>
         * Unlike {@link OnGestureListener#onSingleTapUp(MotionEvent)}, this
         * will only be called after the detector is confident that the user's
         * first tap is not followed by a second tap leading to a double-tap
         * gesture.
         *
         * @param e The down motion event of the single-tap.
         * @return true if the event is consumed, else false
         */
        boolean onSingleTapConfirmed(MotionEvent e); // 点击的确认
 
        /**
         * Notified when a double-tap occurs.
         *
         * @param e The down motion event of the first tap of the double-tap.
         * @return true if the event is consumed, else false
         */
        boolean onDoubleTap(MotionEvent e); // 双击,只通知双击结果

        /**
         * Notified when an event within a double-tap gesture occurs, including
         * the down, move, and up events.
         *
         * @param e The motion event that occurred during the double-tap gesture.
         * @return true if the event is consumed, else false
         */
        boolean onDoubleTapEvent(MotionEvent e); // 这个也是双击，但是包括了双击的 down, move, and up events.我理解就是第二次touch的 down, move, and up events
    }

    /**
     * The listener that is used to notify when a context click occurs. When listening for a
     * context click ensure that you call {@link #onGenericMotionEvent(MotionEvent)} in
     * {@link View#onGenericMotionEvent(MotionEvent)}.
     */
    public interface OnContextClickListener {
        /**
         * Notified when a context click occurs.
         *
         * @param e The motion event that occurred during the context click.
         * @return true if the event is consumed, else false
         */
        boolean onContextClick(MotionEvent e);
    }

    /**
     * A convenience class to extend when you only want to listen for a subset
     * of all the gestures. This implements all methods in the
     * {@link OnGestureListener}, {@link OnDoubleTapListener}, and {@link OnContextClickListener}
     * but does nothing and return {@code false} for all applicable methods.
     */
     这个class就是我们说的，继承了OnGestureListener， OnDoubleTapListener，实现了单指的基本功能。
    public static class SimpleOnGestureListener implements OnGestureListener, OnDoubleTapListener,
            OnContextClickListener {

        public boolean onSingleTapUp(MotionEvent e) {
            return false;
        }

        public void onLongPress(MotionEvent e) {
        }

        public boolean onScroll(MotionEvent e1, MotionEvent e2,
                float distanceX, float distanceY) {
            return false;
        }

        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {
            return false;
        }

        public void onShowPress(MotionEvent e) {
        }

        public boolean onDown(MotionEvent e) {
            return false;
        }

        public boolean onDoubleTap(MotionEvent e) {
            return false;
        }

        public boolean onDoubleTapEvent(MotionEvent e) {
            return false;
        }

        public boolean onSingleTapConfirmed(MotionEvent e) {
            return false;
        }

        public boolean onContextClick(MotionEvent e) {
            return false;
        }
    }

    private int mTouchSlopSquare;
    private int mDoubleTapTouchSlopSquare;
    private int mDoubleTapSlopSquare;
    private int mMinimumFlingVelocity;
    private int mMaximumFlingVelocity;

    private static final int LONGPRESS_TIMEOUT = ViewConfiguration.getLongPressTimeout();
    private static final int TAP_TIMEOUT = ViewConfiguration.getTapTimeout();
    private static final int DOUBLE_TAP_TIMEOUT = ViewConfiguration.getDoubleTapTimeout();
    private static final int DOUBLE_TAP_MIN_TIME = ViewConfiguration.getDoubleTapMinTime();

    // constants for Message.what used by GestureHandler below
    private static final int SHOW_PRESS = 1;
    private static final int LONG_PRESS = 2;
    private static final int TAP = 3;

    private final Handler mHandler;
    private final OnGestureListener mListener;
    private OnDoubleTapListener mDoubleTapListener;
    private OnContextClickListener mContextClickListener;

    private boolean mStillDown;
    private boolean mDeferConfirmSingleTap;
    private boolean mInLongPress;
    private boolean mInContextClick;
    private boolean mAlwaysInTapRegion;
    private boolean mAlwaysInBiggerTapRegion;
    private boolean mIgnoreNextUpEvent;

    private MotionEvent mCurrentDownEvent;
    private MotionEvent mPreviousUpEvent;

    /**
     * True when the user is still touching for the second tap (down, move, and
     * up events). Can only be true if there is a double tap listener attached.
     */
    private boolean mIsDoubleTapping;

    private float mLastFocusX;
    private float mLastFocusY;
    private float mDownFocusX;
    private float mDownFocusY;

    private boolean mIsLongpressEnabled;

    /**
     * Determines speed during touch scrolling
     */
    private VelocityTracker mVelocityTracker;

    /**
     * Consistency verifier for debugging purposes.
     */
    private final InputEventConsistencyVerifier mInputEventConsistencyVerifier =
            InputEventConsistencyVerifier.isInstrumentationEnabled() ?
                    new InputEventConsistencyVerifier(this, 0) : null;

    private class GestureHandler extends Handler {
        GestureHandler() {
            super();
        }

        GestureHandler(Handler handler) {
            super(handler.getLooper());
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case SHOW_PRESS:
                mListener.onShowPress(mCurrentDownEvent);
                break;
                
            case LONG_PRESS:
                dispatchLongPress();
                break;
                
            case TAP:
                // If the user's finger is still down, do not count it as a tap
                if (mDoubleTapListener != null) {
                    if (!mStillDown) {
                        mDoubleTapListener.onSingleTapConfirmed(mCurrentDownEvent);
                    } else {
                        mDeferConfirmSingleTap = true;
                    }
                }
                break;

            default:
                throw new RuntimeException("Unknown message " + msg); //never
            }
        }
    }

    /**
     * Creates a GestureDetector with the supplied listener.
     * This variant of the constructor should be used from a non-UI thread 
     * (as it allows specifying the Handler).
     * 
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use
     *
     * @throws NullPointerException if either {@code listener} or
     * {@code handler} is null.
     *
     * @deprecated Use {@link #GestureDetector(android.content.Context,
     *      android.view.GestureDetector.OnGestureListener, android.os.Handler)} instead.
     */
    @Deprecated
    public GestureDetector(OnGestureListener listener, Handler handler) {
        this(null, listener, handler);
    }

    /**
     * Creates a GestureDetector with the supplied listener.
     * You may only use this constructor from a UI thread (this is the usual situation).
     * @see android.os.Handler#Handler()
     * 
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * 
     * @throws NullPointerException if {@code listener} is null.
     *
     * @deprecated Use {@link #GestureDetector(android.content.Context,
     *      android.view.GestureDetector.OnGestureListener)} instead.
     */
    @Deprecated
    public GestureDetector(OnGestureListener listener) {
        this(null, listener, null);
    }

    /**
     * Creates a GestureDetector with the supplied listener.
     * You may only use this constructor from a {@link android.os.Looper} thread.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public GestureDetector(Context context, OnGestureListener listener) {
        this(context, listener, null);
    }

    /**
     * Creates a GestureDetector with the supplied listener that runs deferred events on the
     * thread associated with the supplied {@link android.os.Handler}.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use for running deferred listener events.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public GestureDetector(Context context, OnGestureListener listener, Handler handler) {
        if (handler != null) {
            mHandler = new GestureHandler(handler);
        } else {
            mHandler = new GestureHandler();
        }
        mListener = listener;
        if (listener instanceof OnDoubleTapListener) {
            setOnDoubleTapListener((OnDoubleTapListener) listener);
        }
        if (listener instanceof OnContextClickListener) {
            setContextClickListener((OnContextClickListener) listener);
        }
        init(context);
    }
    
    /**
     * Creates a GestureDetector with the supplied listener that runs deferred events on the
     * thread associated with the supplied {@link android.os.Handler}.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use for running deferred listener events.
     * @param unused currently not used.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public GestureDetector(Context context, OnGestureListener listener, Handler handler,
            boolean unused) {
        this(context, listener, handler);
    }

    private void init(Context context) {
        if (mListener == null) {
            throw new NullPointerException("OnGestureListener must not be null");
        }
        mIsLongpressEnabled = true;

        // Fallback to support pre-donuts releases
        int touchSlop, doubleTapSlop, doubleTapTouchSlop;
        if (context == null) {
            //noinspection deprecation
            touchSlop = ViewConfiguration.getTouchSlop();
            doubleTapTouchSlop = touchSlop; // Hack rather than adding a hiden method for this
            doubleTapSlop = ViewConfiguration.getDoubleTapSlop();
            //noinspection deprecation
            mMinimumFlingVelocity = ViewConfiguration.getMinimumFlingVelocity();
            mMaximumFlingVelocity = ViewConfiguration.getMaximumFlingVelocity();
        } else {
            final ViewConfiguration configuration = ViewConfiguration.get(context);
            touchSlop = configuration.getScaledTouchSlop();
            doubleTapTouchSlop = configuration.getScaledDoubleTapTouchSlop();
            doubleTapSlop = configuration.getScaledDoubleTapSlop();
            mMinimumFlingVelocity = configuration.getScaledMinimumFlingVelocity();
            mMaximumFlingVelocity = configuration.getScaledMaximumFlingVelocity();
        }
        mTouchSlopSquare = touchSlop * touchSlop;
        mDoubleTapTouchSlopSquare = doubleTapTouchSlop * doubleTapTouchSlop;
        mDoubleTapSlopSquare = doubleTapSlop * doubleTapSlop;
    }

    /**
     * Sets the listener which will be called for double-tap and related
     * gestures.
     * 
     * @param onDoubleTapListener the listener invoked for all the callbacks, or
     *        null to stop listening for double-tap gestures.
     */
    public void setOnDoubleTapListener(OnDoubleTapListener onDoubleTapListener) {
        mDoubleTapListener = onDoubleTapListener;
    }

    /**
     * Sets the listener which will be called for context clicks.
     *
     * @param onContextClickListener the listener invoked for all the callbacks, or null to stop
     *            listening for context clicks.
     */
    public void setContextClickListener(OnContextClickListener onContextClickListener) {
        mContextClickListener = onContextClickListener;
    }

    /**
     * Set whether longpress is enabled, if this is enabled when a user
     * presses and holds down you get a longpress event and nothing further.
     * If it's disabled the user can press and hold down and then later
     * moved their finger and you will get scroll events. By default
     * longpress is enabled.
     *
     * @param isLongpressEnabled whether longpress should be enabled.
     */
    public void setIsLongpressEnabled(boolean isLongpressEnabled) {
        mIsLongpressEnabled = isLongpressEnabled;
    }

    /**
     * @return true if longpress is enabled, else false.
     */
    public boolean isLongpressEnabled() {
        return mIsLongpressEnabled;
    }

    /**
     * Analyzes the given motion event and if applicable triggers the
     * appropriate callbacks on the {@link OnGestureListener} supplied.
     *
     * @param ev The current motion event.
     * @return true if the {@link OnGestureListener} consumed the event,
     *              else false.
     */
    public boolean onTouchEvent(MotionEvent ev) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onTouchEvent(ev, 0);
        }

        final int action = ev.getAction();

        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(ev);

        final boolean pointerUp =
                (action & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_POINTER_UP;
        final int skipIndex = pointerUp ? ev.getActionIndex() : -1;
        final boolean isGeneratedGesture =
                (ev.getFlags() & MotionEvent.FLAG_IS_GENERATED_GESTURE) != 0;

        // Determine focal point
        float sumX = 0, sumY = 0;
        final int count = ev.getPointerCount();
        for (int i = 0; i < count; i++) {
            if (skipIndex == i) continue;
            sumX += ev.getX(i);
            sumY += ev.getY(i);
        }
        final int div = pointerUp ? count - 1 : count;
        final float focusX = sumX / div;
        final float focusY = sumY / div;

        boolean handled = false;

        switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_POINTER_DOWN:
                mDownFocusX = mLastFocusX = focusX;
                mDownFocusY = mLastFocusY = focusY;
                // Cancel long press and taps
                cancelTaps();
                break;

            case MotionEvent.ACTION_POINTER_UP:
                mDownFocusX = mLastFocusX = focusX;
                mDownFocusY = mLastFocusY = focusY;

                // Check the dot product of current velocities.
                // If the pointer that left was opposing another velocity vector, clear.
                mVelocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                final int upIndex = ev.getActionIndex();
                final int id1 = ev.getPointerId(upIndex);
                final float x1 = mVelocityTracker.getXVelocity(id1);
                final float y1 = mVelocityTracker.getYVelocity(id1);
                for (int i = 0; i < count; i++) {
                    if (i == upIndex) continue;

                    final int id2 = ev.getPointerId(i);
                    final float x = x1 * mVelocityTracker.getXVelocity(id2);
                    final float y = y1 * mVelocityTracker.getYVelocity(id2);

                    final float dot = x + y;
                    if (dot < 0) {
                        mVelocityTracker.clear();
                        break;
                    }
                }
                break;

            case MotionEvent.ACTION_DOWN:
                if (mDoubleTapListener != null) {
                    boolean hadTapMessage = mHandler.hasMessages(TAP);
                    if (hadTapMessage) mHandler.removeMessages(TAP);
                    if ((mCurrentDownEvent != null) && (mPreviousUpEvent != null)
                            && hadTapMessage
                            && isConsideredDoubleTap(mCurrentDownEvent, mPreviousUpEvent, ev)) {
                        // This is a second tap
                        mIsDoubleTapping = true;
                        // Give a callback with the first tap of the double-tap
                        handled |= mDoubleTapListener.onDoubleTap(mCurrentDownEvent);
                        // Give a callback with down event of the double-tap
                        handled |= mDoubleTapListener.onDoubleTapEvent(ev);
                    } else {
                        // This is a first tap
                        mHandler.sendEmptyMessageDelayed(TAP, DOUBLE_TAP_TIMEOUT);
                    }
                }

                mDownFocusX = mLastFocusX = focusX;
                mDownFocusY = mLastFocusY = focusY;
                if (mCurrentDownEvent != null) {
                    mCurrentDownEvent.recycle();
                }
                mCurrentDownEvent = MotionEvent.obtain(ev);
                mAlwaysInTapRegion = true;
                mAlwaysInBiggerTapRegion = true;
                mStillDown = true;
                mInLongPress = false;
                mDeferConfirmSingleTap = false;

                if (mIsLongpressEnabled) {
                    mHandler.removeMessages(LONG_PRESS);
                    mHandler.sendEmptyMessageAtTime(LONG_PRESS,
                            mCurrentDownEvent.getDownTime() + LONGPRESS_TIMEOUT);
                }
                mHandler.sendEmptyMessageAtTime(SHOW_PRESS,
                        mCurrentDownEvent.getDownTime() + TAP_TIMEOUT);
                handled |= mListener.onDown(ev);
                break;

            case MotionEvent.ACTION_MOVE:
                if (mInLongPress || mInContextClick) {
                    break;
                }
                final float scrollX = mLastFocusX - focusX;
                final float scrollY = mLastFocusY - focusY;
                if (mIsDoubleTapping) {
                    // Give the move events of the double-tap
                    handled |= mDoubleTapListener.onDoubleTapEvent(ev);
                } else if (mAlwaysInTapRegion) {
                    final int deltaX = (int) (focusX - mDownFocusX);
                    final int deltaY = (int) (focusY - mDownFocusY);
                    int distance = (deltaX * deltaX) + (deltaY * deltaY);
                    int slopSquare = isGeneratedGesture ? 0 : mTouchSlopSquare;
                    if (distance > slopSquare) {
                        handled = mListener.onScroll(mCurrentDownEvent, ev, scrollX, scrollY);
                        mLastFocusX = focusX;
                        mLastFocusY = focusY;
                        mAlwaysInTapRegion = false;
                        mHandler.removeMessages(TAP);
                        mHandler.removeMessages(SHOW_PRESS);
                        mHandler.removeMessages(LONG_PRESS);
                    }
                    int doubleTapSlopSquare = isGeneratedGesture ? 0 : mDoubleTapTouchSlopSquare;
                    if (distance > doubleTapSlopSquare) {
                        mAlwaysInBiggerTapRegion = false;
                    }
                } else if ((Math.abs(scrollX) >= 1) || (Math.abs(scrollY) >= 1)) {
                    handled = mListener.onScroll(mCurrentDownEvent, ev, scrollX, scrollY);
                    mLastFocusX = focusX;
                    mLastFocusY = focusY;
                }
                break;

            case MotionEvent.ACTION_UP:
                mStillDown = false;
                MotionEvent currentUpEvent = MotionEvent.obtain(ev);
                if (mIsDoubleTapping) {
                    // Finally, give the up event of the double-tap
                    handled |= mDoubleTapListener.onDoubleTapEvent(ev);
                } else if (mInLongPress) {
                    mHandler.removeMessages(TAP);
                    mInLongPress = false;
                } else if (mAlwaysInTapRegion && !mIgnoreNextUpEvent) {
                    handled = mListener.onSingleTapUp(ev);
                    if (mDeferConfirmSingleTap && mDoubleTapListener != null) {
                        mDoubleTapListener.onSingleTapConfirmed(ev);
                    }
                } else if (!mIgnoreNextUpEvent) {

                    // A fling must travel the minimum tap distance
                    final VelocityTracker velocityTracker = mVelocityTracker;
                    final int pointerId = ev.getPointerId(0);
                    velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                    final float velocityY = velocityTracker.getYVelocity(pointerId);
                    final float velocityX = velocityTracker.getXVelocity(pointerId);

                    if ((Math.abs(velocityY) > mMinimumFlingVelocity)
                            || (Math.abs(velocityX) > mMinimumFlingVelocity)) {
                        handled = mListener.onFling(mCurrentDownEvent, ev, velocityX, velocityY);
                    }
                }
                if (mPreviousUpEvent != null) {
                    mPreviousUpEvent.recycle();
                }
                // Hold the event we obtained above - listeners may have changed the original.
                mPreviousUpEvent = currentUpEvent;
                if (mVelocityTracker != null) {
                    // This may have been cleared when we called out to the
                    // application above.
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                mIsDoubleTapping = false;
                mDeferConfirmSingleTap = false;
                mIgnoreNextUpEvent = false;
                mHandler.removeMessages(SHOW_PRESS);
                mHandler.removeMessages(LONG_PRESS);
                break;

            case MotionEvent.ACTION_CANCEL:
                cancel();
                break;
        }

        if (!handled && mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onUnhandledEvent(ev, 0);
        }
        return handled;
    }

    /**
     * Analyzes the given generic motion event and if applicable triggers the
     * appropriate callbacks on the {@link OnGestureListener} supplied.
     *
     * @param ev The current motion event.
     * @return true if the {@link OnGestureListener} consumed the event,
     *              else false.
     */
    public boolean onGenericMotionEvent(MotionEvent ev) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onGenericMotionEvent(ev, 0);
        }

        final int actionButton = ev.getActionButton();
        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_BUTTON_PRESS:
                if (mContextClickListener != null && !mInContextClick && !mInLongPress
                        && (actionButton == MotionEvent.BUTTON_STYLUS_PRIMARY
                        || actionButton == MotionEvent.BUTTON_SECONDARY)) {
                    if (mContextClickListener.onContextClick(ev)) {
                        mInContextClick = true;
                        mHandler.removeMessages(LONG_PRESS);
                        mHandler.removeMessages(TAP);
                        return true;
                    }
                }
                break;

            case MotionEvent.ACTION_BUTTON_RELEASE:
                if (mInContextClick && (actionButton == MotionEvent.BUTTON_STYLUS_PRIMARY
                        || actionButton == MotionEvent.BUTTON_SECONDARY)) {
                    mInContextClick = false;
                    mIgnoreNextUpEvent = true;
                }
                break;
        }
        return false;
    }

    private void cancel() {
        mHandler.removeMessages(SHOW_PRESS);
        mHandler.removeMessages(LONG_PRESS);
        mHandler.removeMessages(TAP);
        mVelocityTracker.recycle();
        mVelocityTracker = null;
        mIsDoubleTapping = false;
        mStillDown = false;
        mAlwaysInTapRegion = false;
        mAlwaysInBiggerTapRegion = false;
        mDeferConfirmSingleTap = false;
        mInLongPress = false;
        mInContextClick = false;
        mIgnoreNextUpEvent = false;
    }

    private void cancelTaps() {
        mHandler.removeMessages(SHOW_PRESS);
        mHandler.removeMessages(LONG_PRESS);
        mHandler.removeMessages(TAP);
        mIsDoubleTapping = false;
        mAlwaysInTapRegion = false;
        mAlwaysInBiggerTapRegion = false;
        mDeferConfirmSingleTap = false;
        mInLongPress = false;
        mInContextClick = false;
        mIgnoreNextUpEvent = false;
    }

    private boolean isConsideredDoubleTap(MotionEvent firstDown, MotionEvent firstUp,
            MotionEvent secondDown) {
        if (!mAlwaysInBiggerTapRegion) {
            return false;
        }

        final long deltaTime = secondDown.getEventTime() - firstUp.getEventTime();
        if (deltaTime > DOUBLE_TAP_TIMEOUT || deltaTime < DOUBLE_TAP_MIN_TIME) {
            return false;
        }

        int deltaX = (int) firstDown.getX() - (int) secondDown.getX();
        int deltaY = (int) firstDown.getY() - (int) secondDown.getY();
        final boolean isGeneratedGesture =
                (firstDown.getFlags() & MotionEvent.FLAG_IS_GENERATED_GESTURE) != 0;
        int slopSquare = isGeneratedGesture ? 0 : mDoubleTapSlopSquare;
        return (deltaX * deltaX + deltaY * deltaY < slopSquare);
    }

    private void dispatchLongPress() {
        mHandler.removeMessages(TAP);
        mDeferConfirmSingleTap = false;
        mInLongPress = true;
        mListener.onLongPress(mCurrentDownEvent);
    }
}

2、双指缩放

这个android 原生也实现了，在 frameworks/base/core/java/android/view/ScaleGestureDetector.java里面。我们用的时候只需要去实现ScaleGestureDetector.SimpleOnScaleGestureListener的方法就可以。

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.view;

import android.content.Context;
import android.content.res.Resources;
import android.os.Build;
import android.os.Handler;

/**
 * Detects scaling transformation gestures using the supplied {@link MotionEvent}s.
 * The {@link OnScaleGestureListener} callback will notify users when a particular
 * gesture event has occurred.
 *
 * This class should only be used with {@link MotionEvent}s reported via touch.
 *
 * To use this class:
 * <ul>
 *  <li>Create an instance of the {@code ScaleGestureDetector} for your
 *      {@link View}
 *  <li>In the {@link View#onTouchEvent(MotionEvent)} method ensure you call
 *          {@link #onTouchEvent(MotionEvent)}. The methods defined in your
 *          callback will be executed when the events occur.
 * </ul>
 */
public class ScaleGestureDetector {
    private static final String TAG = "ScaleGestureDetector";

    /**
     * The listener for receiving notifications when gestures occur.
     * If you want to listen for all the different gestures then implement
     * this interface. If you only want to listen for a subset it might
     * be easier to extend {@link SimpleOnScaleGestureListener}.
     *
     * An application will receive events in the following order:
     * <ul>
     *  <li>One {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)}
     *  <li>Zero or more {@link OnScaleGestureListener#onScale(ScaleGestureDetector)}
     *  <li>One {@link OnScaleGestureListener#onScaleEnd(ScaleGestureDetector)}
     * </ul>
     */
    public interface OnScaleGestureListener {
        /**
         * Responds to scaling events for a gesture in progress.
         * Reported by pointer motion.
         *
         * @param detector The detector reporting the event - use this to
         *          retrieve extended info about event state.
         * @return Whether or not the detector should consider this event
         *          as handled. If an event was not handled, the detector
         *          will continue to accumulate movement until an event is
         *          handled. This can be useful if an application, for example,
         *          only wants to update scaling factors if the change is
         *          greater than 0.01.
         */
        public boolean onScale(ScaleGestureDetector detector);

        /**
         * Responds to the beginning of a scaling gesture. Reported by
         * new pointers going down.
         *
         * @param detector The detector reporting the event - use this to
         *          retrieve extended info about event state.
         * @return Whether or not the detector should continue recognizing
         *          this gesture. For example, if a gesture is beginning
         *          with a focal point outside of a region where it makes
         *          sense, onScaleBegin() may return false to ignore the
         *          rest of the gesture.
         */
        public boolean onScaleBegin(ScaleGestureDetector detector);

        /**
         * Responds to the end of a scale gesture. Reported by existing
         * pointers going up.
         *
         * Once a scale has ended, {@link ScaleGestureDetector#getFocusX()}
         * and {@link ScaleGestureDetector#getFocusY()} will return focal point
         * of the pointers remaining on the screen.
         *
         * @param detector The detector reporting the event - use this to
         *          retrieve extended info about event state.
         */
        public void onScaleEnd(ScaleGestureDetector detector);
    }

    /**
     * A convenience class to extend when you only want to listen for a subset
     * of scaling-related events. This implements all methods in
     * {@link OnScaleGestureListener} but does nothing.
     * {@link OnScaleGestureListener#onScale(ScaleGestureDetector)} returns
     * {@code false} so that a subclass can retrieve the accumulated scale
     * factor in an overridden onScaleEnd.
     * {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)} returns
     * {@code true}.
     */
    public static class SimpleOnScaleGestureListener implements OnScaleGestureListener {

        public boolean onScale(ScaleGestureDetector detector) {    // 缩放的过程
            return false;
        }

        public boolean onScaleBegin(ScaleGestureDetector detector) { // 缩放开始
            return true;
        }

        public void onScaleEnd(ScaleGestureDetector detector) {   // 缩放结束
            // Intentionally empty
        }
    }

    private final Context mContext;
    private final OnScaleGestureListener mListener;

    private float mFocusX;
    private float mFocusY;

    private boolean mQuickScaleEnabled;
    private boolean mStylusScaleEnabled;

    private float mCurrSpan;
    private float mPrevSpan;
    private float mInitialSpan;
    private float mCurrSpanX;
    private float mCurrSpanY;
    private float mPrevSpanX;
    private float mPrevSpanY;
    private long mCurrTime;
    private long mPrevTime;
    private boolean mInProgress;
    private int mSpanSlop;
    private int mMinSpan;

    private final Handler mHandler;

    private float mAnchoredScaleStartX;
    private float mAnchoredScaleStartY;
    private int mAnchoredScaleMode = ANCHORED_SCALE_MODE_NONE;

    private static final long TOUCH_STABILIZE_TIME = 128; // ms
    private static final float SCALE_FACTOR = .5f;
    private static final int ANCHORED_SCALE_MODE_NONE = 0;
    private static final int ANCHORED_SCALE_MODE_DOUBLE_TAP = 1;
    private static final int ANCHORED_SCALE_MODE_STYLUS = 2;


    /**
     * Consistency verifier for debugging purposes.
     */
    private final InputEventConsistencyVerifier mInputEventConsistencyVerifier =
            InputEventConsistencyVerifier.isInstrumentationEnabled() ?
                    new InputEventConsistencyVerifier(this, 0) : null;
    private GestureDetector mGestureDetector;

    private boolean mEventBeforeOrAboveStartingGestureEvent;

    /**
     * Creates a ScaleGestureDetector with the supplied listener.
     * You may only use this constructor from a {@link android.os.Looper Looper} thread.
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public ScaleGestureDetector(Context context, OnScaleGestureListener listener) {
        this(context, listener, null);
    }

    /**
     * Creates a ScaleGestureDetector with the supplied listener.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use for running deferred listener events.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public ScaleGestureDetector(Context context, OnScaleGestureListener listener,
                                Handler handler) {
        mContext = context;
        mListener = listener;
        mSpanSlop = ViewConfiguration.get(context).getScaledTouchSlop() * 2;

        final Resources res = context.getResources();
        mMinSpan = res.getDimensionPixelSize(com.android.internal.R.dimen.config_minScalingSpan);
        mHandler = handler;
        // Quick scale is enabled by default after JB_MR2
        final int targetSdkVersion = context.getApplicationInfo().targetSdkVersion;
        if (targetSdkVersion > Build.VERSION_CODES.JELLY_BEAN_MR2) {
            setQuickScaleEnabled(true);
        }
        // Stylus scale is enabled by default after LOLLIPOP_MR1
        if (targetSdkVersion > Build.VERSION_CODES.LOLLIPOP_MR1) {
            setStylusScaleEnabled(true);
        }
    }

    /**
     * Accepts MotionEvents and dispatches events to a {@link OnScaleGestureListener}
     * when appropriate.
     *
     * <p>Applications should pass a complete and consistent event stream to this method.
     * A complete and consistent event stream involves all MotionEvents from the initial
     * ACTION_DOWN to the final ACTION_UP or ACTION_CANCEL.</p>
     *
     * @param event The event to process
     * @return true if the event was processed and the detector wants to receive the
     *         rest of the MotionEvents in this event stream.
     */
    public boolean onTouchEvent(MotionEvent event) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onTouchEvent(event, 0);
        }

        mCurrTime = event.getEventTime();

        final int action = event.getActionMasked();

        // Forward the event to check for double tap gesture
        if (mQuickScaleEnabled) {
            mGestureDetector.onTouchEvent(event);
        }

        final int count = event.getPointerCount();
        final boolean isStylusButtonDown =
                (event.getButtonState() & MotionEvent.BUTTON_STYLUS_PRIMARY) != 0;

        final boolean anchoredScaleCancelled =
                mAnchoredScaleMode == ANCHORED_SCALE_MODE_STYLUS && !isStylusButtonDown;
        final boolean streamComplete = action == MotionEvent.ACTION_UP ||
                action == MotionEvent.ACTION_CANCEL || anchoredScaleCancelled;

        if (action == MotionEvent.ACTION_DOWN || streamComplete) {
            // Reset any scale in progress with the listener.
            // If it's an ACTION_DOWN we're beginning a new event stream.
            // This means the app probably didn't give us all the events. Shame on it.
            if (mInProgress) {
                mListener.onScaleEnd(this);
                mInProgress = false;
                mInitialSpan = 0;
                mAnchoredScaleMode = ANCHORED_SCALE_MODE_NONE;
            } else if (inAnchoredScaleMode() && streamComplete) {
                mInProgress = false;
                mInitialSpan = 0;
                mAnchoredScaleMode = ANCHORED_SCALE_MODE_NONE;
            }

            if (streamComplete) {
                return true;
            }
        }

        if (!mInProgress && mStylusScaleEnabled && !inAnchoredScaleMode()
                && !streamComplete && isStylusButtonDown) {
            // Start of a button scale gesture
            mAnchoredScaleStartX = event.getX();
            mAnchoredScaleStartY = event.getY();
            mAnchoredScaleMode = ANCHORED_SCALE_MODE_STYLUS;
            mInitialSpan = 0;
        }

        final boolean configChanged = action == MotionEvent.ACTION_DOWN ||
                action == MotionEvent.ACTION_POINTER_UP ||
                action == MotionEvent.ACTION_POINTER_DOWN || anchoredScaleCancelled;

        final boolean pointerUp = action == MotionEvent.ACTION_POINTER_UP;
        final int skipIndex = pointerUp ? event.getActionIndex() : -1;

        // Determine focal point
        float sumX = 0, sumY = 0;
        final int div = pointerUp ? count - 1 : count;
        final float focusX;
        final float focusY;
        if (inAnchoredScaleMode()) {
            // In anchored scale mode, the focal pt is always where the double tap
            // or button down gesture started
            focusX = mAnchoredScaleStartX;
            focusY = mAnchoredScaleStartY;
            if (event.getY() < focusY) {
                mEventBeforeOrAboveStartingGestureEvent = true;
            } else {
                mEventBeforeOrAboveStartingGestureEvent = false;
            }
        } else {
            for (int i = 0; i < count; i++) {
                if (skipIndex == i) continue;
                sumX += event.getX(i);
                sumY += event.getY(i);
            }

            focusX = sumX / div;
            focusY = sumY / div;
        }

        // Determine average deviation from focal point
        float devSumX = 0, devSumY = 0;
        for (int i = 0; i < count; i++) {
            if (skipIndex == i) continue;

            // Convert the resulting diameter into a radius.
            devSumX += Math.abs(event.getX(i) - focusX);
            devSumY += Math.abs(event.getY(i) - focusY);
        }
        final float devX = devSumX / div;
        final float devY = devSumY / div;

        // Span is the average distance between touch points through the focal point;
        // i.e. the diameter of the circle with a radius of the average deviation from
        // the focal point.
        final float spanX = devX * 2;
        final float spanY = devY * 2;
        final float span;
        if (inAnchoredScaleMode()) {
            span = spanY;
        } else {
            span = (float) Math.hypot(spanX, spanY);
        }

        // Dispatch begin/end events as needed.
        // If the configuration changes, notify the app to reset its current state by beginning
        // a fresh scale event stream.
        final boolean wasInProgress = mInProgress;
        mFocusX = focusX;
        mFocusY = focusY;
        if (!inAnchoredScaleMode() && mInProgress && (span < mMinSpan || configChanged)) {
            mListener.onScaleEnd(this);
            mInProgress = false;
            mInitialSpan = span;
        }
        if (configChanged) {
            mPrevSpanX = mCurrSpanX = spanX;
            mPrevSpanY = mCurrSpanY = spanY;
            mInitialSpan = mPrevSpan = mCurrSpan = span;
        }

        final int minSpan = inAnchoredScaleMode() ? mSpanSlop : mMinSpan;
        if (!mInProgress && span >=  minSpan &&
                (wasInProgress || Math.abs(span - mInitialSpan) > mSpanSlop)) {
            mPrevSpanX = mCurrSpanX = spanX;
            mPrevSpanY = mCurrSpanY = spanY;
            mPrevSpan = mCurrSpan = span;
            mPrevTime = mCurrTime;
            mInProgress = mListener.onScaleBegin(this);
        }

        // Handle motion; focal point and span/scale factor are changing.
        if (action == MotionEvent.ACTION_MOVE) {
            mCurrSpanX = spanX;
            mCurrSpanY = spanY;
            mCurrSpan = span;

            boolean updatePrev = true;

            if (mInProgress) {
                updatePrev = mListener.onScale(this);
            }

            if (updatePrev) {
                mPrevSpanX = mCurrSpanX;
                mPrevSpanY = mCurrSpanY;
                mPrevSpan = mCurrSpan;
                mPrevTime = mCurrTime;
            }
        }

        return true;
    }

    private boolean inAnchoredScaleMode() {
        return mAnchoredScaleMode != ANCHORED_SCALE_MODE_NONE;
    }

    /**
     * Set whether the associated {@link OnScaleGestureListener} should receive onScale callbacks
     * when the user performs a doubleTap followed by a swipe. Note that this is enabled by default
     * if the app targets API 19 and newer.
     * @param scales true to enable quick scaling, false to disable
     */
    public void setQuickScaleEnabled(boolean scales) {
        mQuickScaleEnabled = scales;
        if (mQuickScaleEnabled && mGestureDetector == null) {
            GestureDetector.SimpleOnGestureListener gestureListener =
                    new GestureDetector.SimpleOnGestureListener() {
                        @Override
                        public boolean onDoubleTap(MotionEvent e) {
                            // Double tap: start watching for a swipe
                            mAnchoredScaleStartX = e.getX();
                            mAnchoredScaleStartY = e.getY();
                            mAnchoredScaleMode = ANCHORED_SCALE_MODE_DOUBLE_TAP;
                            return true;
                        }
                    };
            mGestureDetector = new GestureDetector(mContext, gestureListener, mHandler);
        }
    }

  /**
   * Return whether the quick scale gesture, in which the user performs a double tap followed by a
   * swipe, should perform scaling. {@see #setQuickScaleEnabled(boolean)}.
   */
    public boolean isQuickScaleEnabled() {
        return mQuickScaleEnabled;
    }

    /**
     * Sets whether the associates {@link OnScaleGestureListener} should receive
     * onScale callbacks when the user uses a stylus and presses the button.
     * Note that this is enabled by default if the app targets API 23 and newer.
     *
     * @param scales true to enable stylus scaling, false to disable.
     */
    public void setStylusScaleEnabled(boolean scales) {
        mStylusScaleEnabled = scales;
    }

    /**
     * Return whether the stylus scale gesture, in which the user uses a stylus and presses the
     * button, should perform scaling. {@see #setStylusScaleEnabled(boolean)}
     */
    public boolean isStylusScaleEnabled() {
        return mStylusScaleEnabled;
    }

    /**
     * Returns {@code true} if a scale gesture is in progress.
     */
    public boolean isInProgress() {
        return mInProgress;
    }

    /**
     * Get the X coordinate of the current gesture's focal point.
     * If a gesture is in progress, the focal point is between
     * each of the pointers forming the gesture.
     *
     * If {@link #isInProgress()} would return false, the result of this
     * function is undefined.
     *
     * @return X coordinate of the focal point in pixels.
     */
    public float getFocusX() {
        return mFocusX;
    }

    /**
     * Get the Y coordinate of the current gesture's focal point.
     * If a gesture is in progress, the focal point is between
     * each of the pointers forming the gesture.
     *
     * If {@link #isInProgress()} would return false, the result of this
     * function is undefined.
     *
     * @return Y coordinate of the focal point in pixels.
     */
    public float getFocusY() {
        return mFocusY;
    }

    /**
     * Return the average distance between each of the pointers forming the
     * gesture in progress through the focal point.
     *
     * @return Distance between pointers in pixels.
     */
    public float getCurrentSpan() {
        return mCurrSpan;
    }

    /**
     * Return the average X distance between each of the pointers forming the
     * gesture in progress through the focal point.
     *
     * @return Distance between pointers in pixels.
     */
    public float getCurrentSpanX() {
        return mCurrSpanX;
    }

    /**
     * Return the average Y distance between each of the pointers forming the
     * gesture in progress through the focal point.
     *
     * @return Distance between pointers in pixels.
     */
    public float getCurrentSpanY() {
        return mCurrSpanY;
    }

    /**
     * Return the previous average distance between each of the pointers forming the
     * gesture in progress through the focal point.
     *
     * @return Previous distance between pointers in pixels.
     */
    public float getPreviousSpan() {
        return mPrevSpan;
    }

    /**
     * Return the previous average X distance between each of the pointers forming the
     * gesture in progress through the focal point.
     *
     * @return Previous distance between pointers in pixels.
     */
    public float getPreviousSpanX() {
        return mPrevSpanX;
    }

    /**
     * Return the previous average Y distance between each of the pointers forming the
     * gesture in progress through the focal point.
     *
     * @return Previous distance between pointers in pixels.
     */
    public float getPreviousSpanY() {
        return mPrevSpanY;
    }

    /**
     * Return the scaling factor from the previous scale event to the current
     * event. This value is defined as
     * ({@link #getCurrentSpan()} / {@link #getPreviousSpan()}).
     *
     * @return The current scaling factor.
     */
    public float getScaleFactor() {
        if (inAnchoredScaleMode()) {
            // Drag is moving up; the further away from the gesture
            // start, the smaller the span should be, the closer,
            // the larger the span, and therefore the larger the scale
            final boolean scaleUp =
                    (mEventBeforeOrAboveStartingGestureEvent && (mCurrSpan < mPrevSpan)) ||
                    (!mEventBeforeOrAboveStartingGestureEvent && (mCurrSpan > mPrevSpan));
            final float spanDiff = (Math.abs(1 - (mCurrSpan / mPrevSpan)) * SCALE_FACTOR);
            return mPrevSpan <= 0 ? 1 : scaleUp ? (1 + spanDiff) : (1 - spanDiff);
        }
        return mPrevSpan > 0 ? mCurrSpan / mPrevSpan : 1;
    }

    /**
     * Return the time difference in milliseconds between the previous
     * accepted scaling event and the current scaling event.
     *
     * @return Time difference since the last scaling event in milliseconds.
     */
    public long getTimeDelta() {
        return mCurrTime - mPrevTime;
    }

    /**
     * Return the event time of the current event being processed.
     *
     * @return Current event time in milliseconds.
     */
    public long getEventTime() {
        return mCurrTime;
    }
}

3、多指滑动。

我主要做的有双指和三指的滑动识别，滑动分为直接通知滑动结果和滑动过程实时通知


    private class AiwaysMultiFingerSplit {
        private MotionEvent mStartMutiEvent;
        private MotionEvent mLastEvent;
        private float mLastFocusX;
        private float mLastFocusY;
        private float mDownFocusX;
        private float mDownFocusY;

        public boolean onTouchEvent(MotionEvent ev) {
            if (mVelocityTracker == null) {
                mVelocityTracker = VelocityTracker.obtain();
            }
            mVelocityTracker.addMovement(ev);

            boolean handled = false;
            float sumX = 0, sumY = 0;
            float focusX = 0, focusY = 0;
            int pCount = ev.getPointerCount();
            if (pCount == 2 || pCount == 3) {
                for (int i = 0; i < pCount; i++) {
                        sumX += ev.getX(i);
                        sumY += ev.getY(i);
                }
                focusX = sumX / pCount;
                focusY = sumY / pCount;
            }

            switch(ev.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    mDownFocusX = mLastFocusX = focusX;
                    mDownFocusY = mLastFocusY = focusY;
                    break;
                case MotionEvent.ACTION_UP:
                    if (mVelocityTracker != null) {
                        mVelocityTracker.recycle();
                        mVelocityTracker = null;
                    }
                    if (mLastEvent != null) {
                        mLastEvent = null;
                    }
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    if (pCount == 2 || pCount == 3) {
                        mDownFocusX = mLastFocusX = focusX;
                        mDownFocusY = mLastFocusY = focusY;
                        mStartMutiEvent = MotionEvent.obtain(ev);
                        mLastEvent = MotionEvent.obtain(ev);
                    }
                    handled = true;
                    break;
                case MotionEvent.ACTION_POINTER_UP:
                    Log.d(TAG, "ACTION_POINTER_UP_"+ev.getActionIndex() + " ,onTouchEvent pCount:" + ev.getPointerCount());
                    if ((pCount-1) == 2 || (pCount-1) == 3) {
                        mDownFocusX = mLastFocusX = focusX;
                        mDownFocusY = mLastFocusY = focusY;
                        mStartMutiEvent = MotionEvent.obtain(ev);
                    }

                    if (pCount == 2 || pCount == 3) {
                        final VelocityTracker velocityTracker = mVelocityTracker;
                        velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                        final int id1 = ev.getPointerId(ev.getActionIndex());
                        float sumVX = velocityTracker.getXVelocity(id1);
                        float sumVY = velocityTracker.getYVelocity(id1);
                        for (int i = 0; i < pCount; i++) {
                            if (i == ev.getActionIndex()) continue;

                            final int id2 = ev.getPointerId(i);
                            sumVX += velocityTracker.getXVelocity(id2);
                            sumVY += velocityTracker.getYVelocity(id2);
                        }
                        final float velocityX = sumVX / pCount;
                        final float velocityY = sumVY / pCount;
                        velocityTracker.clear();
						// 这里的处理和onFling一样，关于手指的速度和滑动距离，开始是想把每个手指的滑动和距离都通知出去，但是过程太麻烦，所以上面计算的时候就取了平均值。
                        handled |= notifyMutiFingerSlipAction(mLastEvent, ev, velocityX , velocityY);
                    }
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (pCount == 2 || pCount == 3) { // 判断是2指或3指的时候直接调用notifyMutiFingerSlipProcess来处理，基本和上面的onScroll处理一样
                        final float scrollX = mLastFocusX - focusX;
                        final float scrollY = mLastFocusY - focusY;
                        if ((Math.abs(scrollX) >= 1) || (Math.abs(scrollY) >= 1)) {
                            handled |= notifyMutiFingerSlipProcess(mStartMutiEvent, ev, scrollX, scrollY);
                        }
                        mLastFocusX = focusX;
                        mLastFocusY = focusY;
                        handled = true;
                    }

                    break;
                default:
                    break;
            }
            return handled;
        }
    }

4、总体识别代码

使用的时候只需要new AiwaysGestureManager，然后继承 AiwaysGestureListener 传进子类就可以监听一下事件了

package wayos.car.view;

import android.content.Context;
import android.view.GestureDetector;
import android.view.InputDevice;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.util.Log;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;




public class AiwaysGestureManager {
    private final String TAG = "AiwaysGestureManager";
    private GestureDetector mGestureDetector;
    private ScaleGestureDetector mScaleDetector;
    private AiwaysGestureListener mListener;
    private AiwaysMultiFingerSplit mAiwaysMultiFingerSplit;
    private VelocityTracker mVelocityTracker;
    private int mMinimumFlingVelocity;
    private int mMaximumFlingVelocity;
    private int minVelocity = 50;

    public interface AiwaysGestureListener {
        public boolean onSingleTapUp(MotionEvent motionEvent);
        public boolean onDoubleTap(MotionEvent motionEvent);
        public void onLongPress(MotionEvent e);
        public boolean onDown(MotionEvent e);
        public boolean onUp(MotionEvent motionEvent);
        public boolean onScale(ScaleGestureDetector detector);
        public boolean onScaleBegin(ScaleGestureDetector detector);
        public void onScaleEnd(ScaleGestureDetector detector);
        public boolean singleFingeronSlipProcess(MotionEvent e1, MotionEvent e2, float dx, float dy);
        public boolean singleFingerSlipAction(GestureEvent gestureEvent, MotionEvent startEvent, MotionEvent endEvent, float velocity);
        public boolean mutiFingerSlipProcess(GestureEvent gestureEvent, float startX, float startY, float endX, float endY, float moveX, float moveY);
        public boolean mutiFingerSlipAction(GestureEvent gestureEvent, float startX, float startY, float endX, float endY, float velocityX,float velocityY);
    }

    public enum GestureEvent {
        SINGLE_GINGER_LEFT_SLIP,
        SINGLE_GINGER_RIGHT_SLIP,
        SINGLE_GINGER_UP_SLIP,
        SINGLE_GINGER_DOWN_SLIP,
        DOUBLE_GINGER,
        DOUBLE_GINGER_LEFT_SLIP,
        DOUBLE_GINGER_RIGHT_SLIP,
        DOUBLE_GINGER_UP_SLIP,
        DOUBLE_GINGER_DOWN_SLIP,
        THREE_GINGER,
        THREE_GINGER_UP_SLIP,
        THREE_GINGER_DOWN_SLIP,
        SCALE_START,
        SCALE_MOVE,
        SCALE_END;
    }

    public AiwaysGestureManager(Context context, AiwaysGestureListener listener) {
        mListener = listener;
        mGestureDetector = new GestureDetector(context, new SimpleGesture(), null, true /* ignoreMultitouch */);
        mGestureDetector.setOnDoubleTapListener(new AiwaysDoubleTapListener());
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        mAiwaysMultiFingerSplit = new AiwaysMultiFingerSplit();
        if (context == null) {
            mMinimumFlingVelocity = ViewConfiguration.getMinimumFlingVelocity();
            mMaximumFlingVelocity = ViewConfiguration.getMaximumFlingVelocity();
        } else {
            final ViewConfiguration configuration = ViewConfiguration.get(context);
            mMinimumFlingVelocity = configuration.getScaledMinimumFlingVelocity();
            mMaximumFlingVelocity = configuration.getScaledMaximumFlingVelocity();
        }
    }

    public boolean onTouchEvent(MotionEvent event) {
        final boolean gestureProcessed = mGestureDetector.onTouchEvent(event);
        final boolean scaleProcessed = mScaleDetector.onTouchEvent(event);
        final boolean multiFingerProcessed = mAiwaysMultiFingerSplit.onTouchEvent(event);
        if (event.getAction() == MotionEvent.ACTION_UP) {
            mListener.onUp(event);
        }
        return (gestureProcessed | scaleProcessed | multiFingerProcessed);
    }

    private class SimpleGesture extends GestureDetector.SimpleOnGestureListener {
        @Override
        public void onLongPress(MotionEvent e) {
            mListener.onLongPress(e);
        }

        @Override
        public boolean onScroll(
                MotionEvent e1, MotionEvent e2, float dx, float dy) {
            return mListener.singleFingeronSlipProcess(e1, e2, dx, dy);
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {
            if (e1.getX() - e2.getX() > 0 && Math.abs((int)(e1.getX() - e2.getX())) > Math.abs((int)(e1.getY() - e2.getY()))
                && Math.abs(velocityX) > minVelocity) {
                return mListener.singleFingerSlipAction(GestureEvent.SINGLE_GINGER_LEFT_SLIP, e1, e2, Math.abs(velocityX));
            }

            if (e1.getX() - e2.getX() < 0 && Math.abs((int)(e1.getX() - e2.getX())) > Math.abs((int)(e1.getY() - e2.getY()))
                && Math.abs(velocityX) > minVelocity) {
                return mListener.singleFingerSlipAction(GestureEvent.SINGLE_GINGER_RIGHT_SLIP, e1, e2, Math.abs(velocityX));
            }

            if (e1.getY() - e2.getY() > 0 && Math.abs((int)(e1.getY() - e2.getY())) > Math.abs((int)(e1.getX() - e2.getX()))
                && Math.abs(velocityY) > minVelocity) {
                return mListener.singleFingerSlipAction(GestureEvent.SINGLE_GINGER_UP_SLIP, e1, e2, Math.abs(velocityY));
            }

            if (e1.getY() - e2.getY() < 0 && Math.abs((int)(e1.getY() - e2.getY())) > Math.abs((int)(e1.getX() - e2.getX()))
                && Math.abs(velocityY) > minVelocity) {
                return mListener.singleFingerSlipAction(GestureEvent.SINGLE_GINGER_DOWN_SLIP, e1, e2, Math.abs(velocityY));
            }
            return false;
        }

        @Override
        public boolean onDown(MotionEvent e) {
            mListener.onDown(e);
            return super.onDown(e);
        }
    }

    private class AiwaysDoubleTapListener implements GestureDetector.OnDoubleTapListener {

        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            return mListener.onSingleTapUp(e);
        }

        @Override
        public boolean onDoubleTap(MotionEvent e) {
            return mListener.onDoubleTap(e);
        }

        @Override
        public boolean onDoubleTapEvent(MotionEvent e) {
            return true;
        }
    }

    boolean notifyMutiFingerSlipProcess(MotionEvent startEvent, MotionEvent endEvent, float dX, float dY) {
        int pCount = startEvent.getPointerCount();
        int sumX = 0, sumY = 0;
        for (int i = 0; i < pCount; i++) {
                sumX += startEvent.getX(i);
                sumY += startEvent.getY(i);
        }

        int startX = sumX / pCount;
        int startY = sumY / pCount;

        sumX = sumY =0;
        pCount = endEvent.getPointerCount();
        for (int i = 0; i < pCount; i++) {
                sumX += endEvent.getX(i);
                sumY += endEvent.getY(i);
        }

        int endX = sumX / pCount;
        int endY = sumY / pCount;
        if (pCount == 2) {
            return mListener.mutiFingerSlipProcess(GestureEvent.DOUBLE_GINGER, startX, startY, endX, endY, dX, dY);
        }

        if (pCount == 3) {
            return mListener.mutiFingerSlipProcess(GestureEvent.THREE_GINGER, startX, startY, endX, endY, dX, dY);
        }
        return false;
    }

    boolean notifyMutiFingerSlipAction(MotionEvent startEvent, MotionEvent endEvent, float velocityX, float velocityY) {
        int pCount = startEvent.getPointerCount();
        int sumX = 0, sumY = 0;
        for (int i = 0; i < pCount; i++) {
            sumX += startEvent.getX(i);
            sumY += startEvent.getY(i);
        }

        int startX = sumX / pCount;
        int startY = sumY / pCount;

        sumX = sumY = 0;
        pCount = endEvent.getPointerCount();
        for (int i = 0; i < pCount; i++) {
            sumX += endEvent.getX(i);
            sumY += endEvent.getY(i);
        }

        int endX = sumX / pCount;
        int endY = sumY / pCount;
        Log.d(TAG, "startX:" + startX + " startY:"+startY + " endX: " + endX + " endY: " + endY + " velocityX:" + velocityX + " velocityY: " + velocityY);
        if (pCount == 2) {
            if (startX - endX > 0 && Math.abs(velocityX) > minVelocity
                 && Math.abs(startX - endX) > Math.abs(startY - endY)) {
                Log.d(TAG, "DOUBLE_GINGER_LEFT_SLIP");
                return mListener.mutiFingerSlipAction(GestureEvent.DOUBLE_GINGER_LEFT_SLIP, startX , startY, endX, endY, velocityX, velocityY);
            }

            if (startX - endX < 0 && Math.abs(velocityX) > minVelocity
                 && Math.abs(startX - endX) > Math.abs(startY - endY)) {
                Log.d(TAG, "DOUBLE_GINGER_RIGHT_SLIP");
                return mListener.mutiFingerSlipAction(GestureEvent.DOUBLE_GINGER_RIGHT_SLIP, startX , startY, endX, endY, velocityX, velocityY);
            }

            if (startY - endY > 0 && Math.abs(velocityY) > minVelocity
                 && Math.abs(startY - endY) > Math.abs(startX - endX)) {
                Log.d(TAG, "DOUBLE_GINGER_UP_SLIP");
                return mListener.mutiFingerSlipAction(GestureEvent.DOUBLE_GINGER_UP_SLIP, startX , startY, endX, endY, velocityX, velocityY);
            }

            if (startY - endY < 0 && Math.abs(velocityY) > minVelocity
                 && Math.abs(startY - endY) > Math.abs(startX - endX)) {
                Log.d(TAG, "DOUBLE_GINGER_DOWN_SLIP");
                return mListener.mutiFingerSlipAction(GestureEvent.DOUBLE_GINGER_DOWN_SLIP, startX , startY, endX, endY, velocityX, velocityY);
            }
        }
        if (pCount == 3) {
            if (startY - endY > 0 && Math.abs(velocityY) > minVelocity
                 && Math.abs(startY - endY) > Math.abs(startX - endX)) {
                Log.d(TAG, "THREE_GINGER_UP_SLIP");
                return mListener.mutiFingerSlipAction(GestureEvent.THREE_GINGER_UP_SLIP, startX , startY, endX, endY, velocityX, velocityY);
            }

            if (startY - endY < 0 && Math.abs(velocityY) > minVelocity
                 && Math.abs(startY - endY) > Math.abs(startX - endX)) {
                Log.d(TAG, "THREE_GINGER_DOWN_SLIP");
                return mListener.mutiFingerSlipAction(GestureEvent.THREE_GINGER_DOWN_SLIP, startX , startY, endX, endY, velocityX, velocityY);
            }
        }
        return false;
    }


    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            Log.d(TAG, "onScaleBegin");
            return mListener.onScaleBegin(detector);
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            Log.d(TAG, "onScaling");
            return mListener.onScale(detector);
        }

        @Override
        public void onScaleEnd(ScaleGestureDetector detector) {
            Log.d(TAG, "onScaleEnd");
            mListener.onScaleEnd(detector);
        }
    }

    private class AiwaysMultiFingerSplit {
        private MotionEvent mStartMutiEvent;
        private MotionEvent mLastEvent;
        private float mLastFocusX;
        private float mLastFocusY;
        private float mDownFocusX;
        private float mDownFocusY;

        public boolean onTouchEvent(MotionEvent ev) {
            if (mVelocityTracker == null) {
                mVelocityTracker = VelocityTracker.obtain();
            }
            mVelocityTracker.addMovement(ev);

            boolean handled = false;
            float sumX = 0, sumY = 0;
            float focusX = 0, focusY = 0;
            int pCount = ev.getPointerCount();
            if (pCount == 2 || pCount == 3) {
                for (int i = 0; i < pCount; i++) {
                        sumX += ev.getX(i);
                        sumY += ev.getY(i);
                }
                focusX = sumX / pCount;
                focusY = sumY / pCount;
            }

            switch(ev.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    mDownFocusX = mLastFocusX = focusX;
                    mDownFocusY = mLastFocusY = focusY;
                    break;
                case MotionEvent.ACTION_UP:
                    if (mVelocityTracker != null) {
                        mVelocityTracker.recycle();
                        mVelocityTracker = null;
                    }
                    if (mLastEvent != null) {
                        mLastEvent = null;
                    }
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    if (pCount == 2 || pCount == 3) {
                        mDownFocusX = mLastFocusX = focusX;
                        mDownFocusY = mLastFocusY = focusY;
                        mStartMutiEvent = MotionEvent.obtain(ev);
                        mLastEvent = MotionEvent.obtain(ev);
                    }
                    handled = true;
                    break;
                case MotionEvent.ACTION_POINTER_UP:
                    Log.d(TAG, "ACTION_POINTER_UP_"+ev.getActionIndex() + " ,onTouchEvent pCount:" + ev.getPointerCount());
                    if ((pCount-1) == 2 || (pCount-1) == 3) {
                        mDownFocusX = mLastFocusX = focusX;
                        mDownFocusY = mLastFocusY = focusY;
                        mStartMutiEvent = MotionEvent.obtain(ev);
                    }

                    if (pCount == 2 || pCount == 3) {
                        final VelocityTracker velocityTracker = mVelocityTracker;
                        velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                        final int id1 = ev.getPointerId(ev.getActionIndex());
                        float sumVX = velocityTracker.getXVelocity(id1);
                        float sumVY = velocityTracker.getYVelocity(id1);
                        for (int i = 0; i < pCount; i++) {
                            if (i == ev.getActionIndex()) continue;

                            final int id2 = ev.getPointerId(i);
                            sumVX += velocityTracker.getXVelocity(id2);
                            sumVY += velocityTracker.getYVelocity(id2);
                        }
                        final float velocityX = sumVX / pCount;
                        final float velocityY = sumVY / pCount;
                        velocityTracker.clear();

                        handled |= notifyMutiFingerSlipAction(mLastEvent, ev, velocityX , velocityY);
                    }
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (pCount == 2 || pCount == 3) {
                        final float scrollX = mLastFocusX - focusX;
                        final float scrollY = mLastFocusY - focusY;
                        if ((Math.abs(scrollX) >= 1) || (Math.abs(scrollY) >= 1)) {
                            handled |= notifyMutiFingerSlipProcess(mStartMutiEvent, ev, scrollX, scrollY);
                        }
                        mLastFocusX = focusX;
                        mLastFocusY = focusY;
                        handled = true;
                    }

                    break;
                default:
                    break;
            }
            return handled;
        }
    }
}