摘要：本文主要针对客户需求将Launcher3删除风格从顶部修改为在图标旁显示。本文先从android 5.1，高通msm8916平台，对Launcher3的删除显示风格进行分析，然后在此基础上将新的删除风格添加到相应的代码中。

1.Launcher3删除流程分析

Launcher3原生的删除风格是长按图标，会在顶部中间出复现删除区域，通过拖动图标至删除区域实现接下来的删除操作。通过logcat分析，发现删除是调用系统的PackageInstaller.apk里的接口实现的，根据经验全局搜索Intent.ACTION_DELETE在Launcher.java中找到代码位置：

packages/apps/Launcher3/src/com/android/launcher3/Launcher.java
    // returns true if the activity was started
    boolean startApplicationUninstallActivity(ComponentName componentName, int flags) {
        if ((flags & AppInfo.DOWNLOADED_FLAG) == 0) {
            // System applications cannot be installed. For now, show a toast explaining that.
            // We may give them the option of disabling apps this way.
            int messageId = R.string.uninstall_system_app_text;
            Toast.makeText(this, messageId, Toast.LENGTH_SHORT).show();
            return false;
        } else {
            String packageName = componentName.getPackageName();
            String className = componentName.getClassName();
            Intent intent = new Intent(
                    Intent.ACTION_DELETE, Uri.fromParts("package", packageName, className));
            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
                    Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
            startActivity(intent);
            return true;
        }
    }

找到最终实现删除的代码，就可以通过在方法入口处添加log追踪trace：

android.util.Log.d(TAG, "trace: ", new Exception());

packages/apps/Launcher3/src/com/android/launcher3/DeleteDropTarget.java
    private void completeDrop(DragObject d) {
        ItemInfo item = (ItemInfo) d.dragInfo;
        boolean wasWaitingForUninstall = mWaitingForUninstall;
        mWaitingForUninstall = false;
        if (isAllAppsApplication(d.dragSource, item)) {
            // Uninstall the application if it is being dragged from AppsCustomize
            AppInfo appInfo = (AppInfo) item;
            mLauncher.startApplicationUninstallActivity(appInfo.componentName, appInfo.flags);
        } else if (isUninstallFromWorkspace(d)) {
            ShortcutInfo shortcut = (ShortcutInfo) item;
            if (shortcut.intent != null && shortcut.intent.getComponent() != null) {
                final ComponentName componentName = shortcut.intent.getComponent();
                final DragSource dragSource = d.dragSource;
                int flags = AppInfo.initFlags(
                    ShortcutInfo.getPackageInfo(getContext(), componentName.getPackageName()));
                mWaitingForUninstall =
                    mLauncher.startApplicationUninstallActivity(componentName, flags); // 此处调用
                if (mWaitingForUninstall) {
                    final Runnable checkIfUninstallWasSuccess = new Runnable() {
                        @Override
                        public void run() {
                            mWaitingForUninstall = false;
                            String packageName = componentName.getPackageName();
                            List<ResolveInfo> activities =
                                    AllAppsList.findActivitiesForPackage(getContext(), packageName);
                            boolean uninstallSuccessful = activities.size() == 0;
                            if (dragSource instanceof Folder) {
                                ((Folder) dragSource).
                                    onUninstallActivityReturned(uninstallSuccessful);
                            } else if (dragSource instanceof Workspace) {
                                ((Workspace) dragSource).
                                    onUninstallActivityReturned(uninstallSuccessful);
                            }
                        }
                    };
                    mLauncher.addOnResumeCallback(checkIfUninstallWasSuccess);
                }
            }
        } else if (isWorkspaceOrFolderApplication(d)) {
            LauncherModel.deleteItemFromDatabase(mLauncher, item);
        } else if (isWorkspaceFolder(d)) {
            // Remove the folder from the workspace and delete the contents from launcher model
            FolderInfo folderInfo = (FolderInfo) item;
            mLauncher.removeFolder(folderInfo);
            LauncherModel.deleteFolderContentsFromDatabase(mLauncher, folderInfo);
        } else if (isWorkspaceOrFolderWidget(d)) {
            // Remove the widget from the workspace
            mLauncher.removeAppWidget((LauncherAppWidgetInfo) item);
            LauncherModel.deleteItemFromDatabase(mLauncher, item);

            final LauncherAppWidgetInfo launcherAppWidgetInfo = (LauncherAppWidgetInfo) item;
            final LauncherAppWidgetHost appWidgetHost = mLauncher.getAppWidgetHost();
            if (appWidgetHost != null) {
                // Deleting an app widget ID is a void call but writes to disk before returning
                // to the caller...
                new AsyncTask<Void, Void, Void>() {
                    public Void doInBackground(Void ... args) {
                        appWidgetHost.deleteAppWidgetId(launcherAppWidgetInfo.appWidgetId);
                        return null;
                    }
                }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, (Void) null);
            }
        }
        if (wasWaitingForUninstall && !mWaitingForUninstall) {
            if (d.dragSource instanceof Folder) {
                ((Folder) d.dragSource).onUninstallActivityReturned(false);
            } else if (d.dragSource instanceof Workspace) {
                ((Workspace) d.dragSource).onUninstallActivityReturned(false);
            }
        }
    }

2. 添加新的删除风格

可见操作是在onDrop这类操作之后判断执行的。
通过trace我们确定了添加代码的位置在workspace.java中的startDrag方法中比较合理。

packages/apps/Launcher3/src/com/android/launcher3/Workspace.java
    void startDrag(CellLayout.CellInfo cellInfo) {
        View child = cellInfo.cell;

        // Make sure the drag was started by a long press as opposed to a long click.
        if (!child.isInTouchMode()) {
            return;
        }

        mDragInfo = cellInfo;
        child.setVisibility(INVISIBLE);
        CellLayout layout = (CellLayout) child.getParent().getParent();
        layout.prepareChildForDrag(child);

        child.clearFocus();
        child.setPressed(false);

        final Canvas canvas = new Canvas();

        // The outline is used to visualize where the item will land if dropped
        mDragOutline = createDragOutline(child, canvas, DRAG_BITMAP_PADDING);
        beginDragShared(child, this);
        // modify @ + {
        Object dragInfo = cellInfo.cell.getTag();
        if (cellInfo.cell.getTag() instanceof ItemInfo) {
            ItemInfo item = (ItemInfo) dragInfo;
            if (item instanceof ShortcutInfo) {
                ShortcutInfo shortcutInfo = (ShortcutInfo) item;
                if (shortcutInfo.intent != null && shortcutInfo.intent.getComponent() != null) {
                    ComponentName componentName = shortcutInfo.intent.getComponent();
                    if (DeleteDropTarget.willAcceptDrop(child.getTag())) {
                        showDialog(cellInfo.cell, componentName);
                    }
                }
            }
        }
        // modify @ + }
    }

    // modify @ + {
    private PopupWindow popupWindow;
    private TextView tvDelete;
    private void showDialog(View v, final ComponentName componentName) {
        View popView = LayoutInflater.from(getContext()).inflate(R.layout.layout_long_click_dialog, null);
        tvDelete=(TextView) popView.findViewById(R.id.delete_target_tv);
        tvDelete.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                if (popupWindow.isShowing()) {
                    popupWindow.dismiss();
                }
                int flags = AppInfo.initFlags(
                        ShortcutInfo.getPackageInfo(getContext(), componentName.getPackageName()));
                boolean mWaitingForUninstall =
                        mLauncher.startApplicationUninstallActivity(componentName, flags);
            }
        });
        popupWindow = new PopupWindow(popView, ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, true);
        popupWindow.setOutsideTouchable(true);
        popupWindow.setBackgroundDrawable(new BitmapDrawable());
        if (popupWindow.isShowing()) {
            popupWindow.dismiss();
        }
        int deleteHeight = tvDelete.getHeight() == 0 ? 280 : tvDelete.getHeight();
        int deleteWidth = tvDelete.getWidth() == 0 ? 212 : tvDelete.getWidth();
        popupWindow.showAsDropDown(v, (v.getWidth() - deleteWidth) / 2, v.getHeight() - deleteHeight);
    }
    // modify @ + }

deleteHeight和deleteWidth是在调试很多次之后确定的最佳位置。

新风格需要在长按图标时显示删除选项，同时在拖动图标时，自然就不显示了：

public void onDragOver(DragObject d) {
    // modify @ + {
    if (null != popupWindow && popupWindow.isShowing()) {
        popupWindow.dismiss();
    }
    // modify @ + }
    ...
}

layout文件：

packages/apps/Launcher3/res/layout/layout_long_click_dialog.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/white" >

    <TextView
        android:id="@+id/delete_target_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:padding="5dp"
        android:drawableTop="@drawable/ic_launcher_trashcan_normal_holo"
        android:text="@string/delete_target_uninstall_label"
        android:textColor="@android:color/black" />

</LinearLayout>

3. 隐藏原生删除区域

另外，原生删除中有判断是否是系统apk，如果是则不弹删除区域，我们需要此判断，同时不显示原生的删除区域：

packages/apps/Launcher3/src/com/android/launcher3/DeleteDropTarget.java
    @Override
    public void onDragStart(DragSource source, Object info, int dragAction) {
        boolean isVisible = true;
        boolean useUninstallLabel = !LauncherAppState.isDisableAllApps() &&
                isAllAppsApplication(source, info);
        boolean useDeleteLabel = !useUninstallLabel && source.supportsDeleteDropTarget();

        // If we are dragging an application from AppsCustomize, only show the control if we can
        // delete the app (it was downloaded), and rename the string to "uninstall" in such a case.
        // Hide the delete target if it is a widget from AppsCustomize.
        if (!willAcceptDrop(info) || isAllAppsWidget(source, info)) {
            isVisible = false;
        }

        if (useUninstallLabel) {
            setCompoundDrawablesRelativeWithIntrinsicBounds(mUninstallDrawable, null, null, null);
        } else if (useDeleteLabel) {
            setCompoundDrawablesRelativeWithIntrinsicBounds(mRemoveDrawable, null, null, null);
        } else {
            isVisible = false;
        }
        mCurrentDrawable = (TransitionDrawable) getCurrentDrawable();

        mActive = isVisible;
        resetHoverColor();
        ((ViewGroup) getParent()).setVisibility(isVisible ? View.VISIBLE : View.GONE);
        if (isVisible && getText().length() > 0) {
            setText(useUninstallLabel ? R.string.delete_target_uninstall_label
                : R.string.delete_target_label);
        }
    }

通过添加log发现willAcceptDrop判断是否是系统应用，当然，我们始终将isVisible设置为false，则原生的删除区域就不会显示了。

本文地址：https://blog.csdn.net/qq_28534581/article/details/107457415

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