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所谓事件分发，就是将一次完整的点击所包含的点击事件传递到某个具体的view或viewgroup，让该view或该viewgroup处理它（消费它）。分发是从上往下（父到子）依次传递的，其中可能经过的对象有最上层activity，中间层viewgroup，最下层view。
源码查找：
1.自己的activity的setcontentview()方法
我要评论 @override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_event_distribution);
}
2.跳转到activity.java的setcontentview()方法，可以看到，调用了getwindow()的方法
public void setcontentview(@layoutres int layoutresid) {
getwindow().setcontentview(layoutresid);
initwindowdecoractionbar();
}
3.activity.java的mwindow来自phonewindow
mwindow = new phonewindow(this, window, activityconfigcallback);
4.phonewindow.java-->setcontentview()--> installdecor()，在phonewindow中调用了installdecor()方法
@override
public void setcontentview(int layoutresid) {
// note: feature_content_transitions may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. do not check the feature
// before this happens.
if (mcontentparent == null) {
installdecor(); //继续执行
} else if (!hasfeature(feature_content_transitions)) {
mcontentparent.removeallviews();
}
..................
5.phonewindow.java-->setcontentview()--> installdecor()--> generatelayout(mdecor)，在 installdecor()中又继续执行了generatelayout(mdecor)方法。
mcontentparent = generatelayout(mdecor);
6.phonewindow.java-->generatelayout()
viewgroup generatelayout(decorview decor)
7.phonewindow.java-->generatelayout()--> int layoutresource，layoutresource根据不同情况，返回不同的资源文件，也就是布局文件。
int layoutresource;
8.phonewindow.java-->generatelayout()-->r.layout.screen_title; 拿出一个常用的布局文件，screen_title.xml
layoutresource = r.layout.screen_title;
9.screen_title.xml的代码， viewstub是用来显示actionbar的，另外两个framelayout，一个显示titleview，一个显示contentview，平时写的内容，正是contentview。
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:fitssystemwindows="true">
<!-- popout bar for action modes -->
<viewstub android:id="@+id/action_mode_bar_stub"
android:inflatedid="@+id/action_mode_bar"
android:layout="@layout/action_mode_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="?attr/actionbartheme" />
<framelayout
android:layout_width="match_parent"
android:layout_height="?android:attr/windowtitlesize"
style="?android:attr/windowtitlebackgroundstyle">
<textview android:id="@android:id/title"
style="?android:attr/windowtitlestyle"
android:background="@null"
android:fadingedge="horizontal"
android:gravity="center_vertical"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</framelayout>
<framelayout android:id="@android:id/content"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:foregroundgravity="fill_horizontal|top"
android:foreground="?android:attr/windowcontentoverlay" />
</linearlayout>
如以下结构图：
涉及到的方法
@override
public boolean dispatchtouchevent(motionevent ev) {
//分发事件
return super.dispatchtouchevent(ev);
}
@override
public boolean onintercepttouchevent(motionevent ev) {
//拦截事件
return super.onintercepttouchevent(ev);
}
@override
public boolean ontouchevent(motionevent event) {
//消费事件
return super.ontouchevent(event);
}
activity涉及到的方法：dispatchtouchevent()、ontouchevent()
viewgroup涉及到的方法：dispatchtouchevent()、onintercepttouchevent()
view涉及到的方法：dispatchtouchevent()、ontouchevent()
每一次事件分发，都是从dispatchtouchevent()开始的。
1）查看activity的源码，调用了getwindow().superdispatchtouchevent(ev)
public boolean dispatchtouchevent(motionevent ev) {
if (ev.getaction() == motionevent.action_down) {
onuserinteraction();
}
if (getwindow().superdispatchtouchevent(ev)) {
return true;
}
return ontouchevent(ev);
}
2）在activity.java中可以看到，所以getwindow().superdispatchtouchevent(ev)实际上是调用了phonewindow.java中的superdispatchtouchevent(ev)方法。
public window getwindow() {
return mwindow;
}
mwindow = new phonewindow(this, window, activityconfigcallback); //mwindow的定义
3）然后再看phonewindow.java中的superdispatchtouchevent(ev)方法，是调用decorview.java的mdecor.superdispatchtouchevent(event)
@override
public boolean superdispatchtouchevent(motionevent event) {
return mdecor.superdispatchtouchevent(event);
}
4）而decorview是继承framelayout，再继承viewgroup的
private decorview mdecor; //实例对象 class decorview extends framelayout; //继承framelayout framelayout extends viewgroup; //继承viewgroup
5）从上面四步来分析，avtivity的getwindow().superdispatchtouchevent()方法最后调用的是viewgroup的dispatchtouchevent()方法，从而实现了事件从activity的dispatchtouchevent()向下传递到viewgroup的dispatchtouchevent()方法。
6）返回值分析。
getwindow().superdispatchtouchevent()返回true，则avtivity的dispatchtouchevent()，也会返回true，表示点击事件顺利分发给viewgroup，由viewgroup继续进行下一层的分发，avtivity的分发任务结束。
ontouchevent()，无论ontouchevent()这个方法返回的是true或者false，本次的事件分发都结束了。
viewgroup.java中的部分代码
viewgroup-->dispatchtouchevent()
public boolean dispatchtouchevent(motionevent ev) {
if (!disallowintercept) {
intercepted = onintercepttouchevent(ev);
ev.setaction(action); // restore action in case it was changed
} else {
intercepted = false;
}
}
方法中使用了onintercepttouchevent(ev)方法
onintercepttouchevent(ev)默认返回不拦截，可以在viewgroup中重写改方法来拦截事件。
这个源码中，使用到了intercepted这个变量，主要作用是来遍历子viewgroup和view，
// check for interception.
final boolean intercepted;
if (!canceled && !intercepted) {
// if the event is targeting accessibility focus we give it to the
// view that has accessibility focus and if it does not handle it
// we clear the flag and dispatch the event to all children as usual.
// we are looking up the accessibility focused host to avoid keeping
// state since these events are very rare.
view childwithaccessibilityfocus = ev.istargetaccessibilityfocus()
? findchildwithaccessibilityfocus() : null;
view的dispatchtouchevent()的源码
public boolean dispatchtouchevent(motionevent event) {
// if the event should be handled by accessibility focus first.
if (event.istargetaccessibilityfocus()) {
// we don't have focus or no virtual descendant has it, do not handle the event.
if (!isaccessibilityfocusedvieworhost()) {
return false;
}
// we have focus and got the event, then use normal event dispatch.
event.settargetaccessibilityfocus(false);
}
boolean result = false;
if (minputeventconsistencyverifier != null) {
minputeventconsistencyverifier.ontouchevent(event, 0);
}
final int actionmasked = event.getactionmasked();
if (actionmasked == motionevent.action_down) {
// defensive cleanup for new gesture
stopnestedscroll();
}
if (onfiltertoucheventforsecurity(event)) {
if ((mviewflags & enabled_mask) == enabled && handlescrollbardragging(event)) {
result = true;
}
//noinspection simplifiableifstatement
listenerinfo li = mlistenerinfo;
if (li != null && li.montouchlistener != null
&& (mviewflags & enabled_mask) == enabled
&& li.montouchlistener.ontouch(this, event)) {
result = true;
}
if (!result && ontouchevent(event)) {
result = true;
}
}
if (!result && minputeventconsistencyverifier != null) {
minputeventconsistencyverifier.onunhandledevent(event, 0);
}
// clean up after nested scrolls if this is the end of a gesture;
// also cancel it if we tried an action_down but we didn't want the rest
// of the gesture.
if (actionmasked == motionevent.action_up ||
actionmasked == motionevent.action_cancel ||
(actionmasked == motionevent.action_down && !result)) {
stopnestedscroll();
}
return result;
}
ontouch()方法，如果ontouch()方法能够消费该事件，就会直接返回true，从而直接结束view的dispatchtouchevent()方法，不再执行ontouchevent()方法；
ontouchevent``()方法。
viewgroup的ontouchevent()方法，直到回调到activity的ontouchevent``()方法。
共有三种类型和四个测试代码
activity：eventdistributionactivity
viewgroup：eventdistributionlinearlayout1、eventdistributionlinearlayout2
view：eventdistributionbutton
分别代码：
eventdistributionactivity.java
public class eventdistributionactivity extends baseactivity {
button mbtn;
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_event_distribution);
mbtn = findviewbyid(r.id.btn);
onclick();
}
public void onclick() {
mbtn.setonclicklistener(new view.onclicklistener() {
@override
public void onclick(view v) {
log.v("showlog", "按钮被点击！");
}
});
mbtn.setontouchlistener(new view.ontouchlistener() {
@override
public boolean ontouch(view v, motionevent event) {
boolean dis = false;
log.v("showlog", "button.touch()=" + dis);
return dis;
}
});
}
@override
public boolean dispatchtouchevent(motionevent ev) {
//分发事件
boolean dis = super.dispatchtouchevent(ev);
log.v("showlog", "activity.dispatchtouchevent()=" + dis);
return dis;
}
@override
public boolean ontouchevent(motionevent event) {
//处理事件
boolean dis = super.ontouchevent(event);
log.v("showlog", "activity.ontouchevent()=" + dis);
return dis;
}
}
eventdistributionlinearlayout1.java
public class eventdistributionlinearlayout1 extends linearlayout {
public eventdistributionlinearlayout1(context context, attributeset attrs) {
super(context, attrs);
}
@override
public boolean dispatchtouchevent(motionevent ev) {
//分发事件
boolean dis = super.dispatchtouchevent(ev);
log.v("showlog", "linearlayout1.dispatchtouchevent()=" + dis);
return dis;
}
@override
public boolean onintercepttouchevent(motionevent ev) {
//拦截事件
boolean dis = super.onintercepttouchevent(ev);
log.v("showlog", "linearlayout1.onintercepttouchevent()=" + dis);
return dis;
}
@override
public boolean ontouchevent(motionevent event) {
//消费事件
boolean dis = super.ontouchevent(event);
log.v("showlog", "linearlayout1.ontouchevent()=" + dis);
return dis;
}
}
eventdistributionlinearlayout2.java
public class eventdistributionlinearlayout2 extends linearlayout {
public eventdistributionlinearlayout2(context context, attributeset attrs) {
super(context, attrs);
}
@override
public boolean dispatchtouchevent(motionevent ev) {
//分发事件
boolean dis = super.dispatchtouchevent(ev);
log.v("showlog", "linearlayout2.dispatchtouchevent()=" + dis);
return dis;
}
@override
public boolean onintercepttouchevent(motionevent ev) {
//拦截事件
boolean dis = super.onintercepttouchevent(ev);
dis = true;
log.v("showlog", "linearlayout2.onintercepttouchevent()=" + dis);
return dis;
}
@override
public boolean ontouchevent(motionevent event) {
//消费事件
boolean dis = super.ontouchevent(event);
log.v("showlog", "linearlayout2.ontouchevent()=" + dis);
return dis;
}
}
eventdistributionbutton.java
public class eventdistributionbutton extends button {
public eventdistributionbutton(context context, attributeset attrs) {
super(context, attrs);
}
@override
public boolean dispatchtouchevent(motionevent event) {
//分发事件
boolean dis = super.dispatchtouchevent(event);
log.v("showlog", "button.dispatchtouchevent()=" + dis);
return dis;
}
@override
public boolean ontouchevent(motionevent event) {
//消费事件
boolean dis = super.ontouchevent(event);
log.v("showlog", "button.ontouchevent()=" + dis);
return dis;
}
@override
public boolean performclick() {
boolean dis = super.performclick();
log.v("showlog", "button.performclick()="+dis);
return dis;
}
}
activity_event_distribution.xml
<?xml version="1.0" encoding="utf-8"?>
<com.lanjiabin.systemtest.event.eventdistributionlinearlayout1 xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".event.eventdistributionactivity">
<com.lanjiabin.systemtest.event.eventdistributionlinearlayout2
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<com.lanjiabin.systemtest.event.eventdistributionbutton
android:background="@drawable/button_color_circle_shape1"
android:id="@+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margintop="300dp"
android:text="点击" />
</com.lanjiabin.systemtest.event.eventdistributionlinearlayout2>
</com.lanjiabin.systemtest.event.eventdistributionlinearlayout1>
效果图：一个linearlayout1包含linearlayout2再包含一个button
界面只有一个按钮
测试用例：按钮消费事件，和空白处不消费事件
按住按钮不松开,事件被button的ontouchevent()消费
linearlayout1.onintercepttouchevent()=false linearlayout2.onintercepttouchevent()=false button.touch()=false button.ontouchevent()=true button.dispatchtouchevent()=true linearlayout2.dispatchtouchevent()=true linearlayout1.dispatchtouchevent()=true activity.dispatchtouchevent()=true
按住空白处不松开，没有事件被消费
linearlayout1.onintercepttouchevent()=false linearlayout2.onintercepttouchevent()=false linearlayout2.ontouchevent()=false linearlayout2.dispatchtouchevent()=false linearlayout1.ontouchevent()=false linearlayout1.dispatchtouchevent()=false activity.ontouchevent()=false activity.dispatchtouchevent()=false
测试用例：在linearlayout2处截断
修改代码：eventdistributionlinearlayout2.java
@override
public boolean onintercepttouchevent(motionevent ev) {
//拦截事件
boolean dis = super.onintercepttouchevent(ev);
dis = true;
log.v("showlog", "linearlayout2.onintercepttouchevent()=" + dis);
return dis;
}
按住按钮不松开：事件截断生效，将不会继续遍历下层的viewgroup或者view，所以日志中看不到button的日志打印。
linearlayout1.onintercepttouchevent()=false linearlayout2.onintercepttouchevent()=true //截断生效 linearlayout2.ontouchevent()=false linearlayout2.dispatchtouchevent()=false linearlayout1.ontouchevent()=false linearlayout1.dispatchtouchevent()=false activity.ontouchevent()=false activity.dispatchtouchevent()=false
测试用例：在view中ontouch()中返回true
也就是在button中设置ontouch()返回true，则不会产生点击事件，完整的点击事件是被按下和松开的，所以上面没有点击按钮的监听事件的打印日志。
首先，看看完整的点击事件日志，去掉先前测试的改变的代码。
linearlayout1.onintercepttouchevent()=false linearlayout2.onintercepttouchevent()=false button.touch()=false button.ontouchevent()=true //触摸按下事件被消费 button.dispatchtouchevent()=true linearlayout2.dispatchtouchevent()=true linearlayout1.dispatchtouchevent()=true activity.dispatchtouchevent()=true //触摸按下的事件处理结束 linearlayout1.onintercepttouchevent()=false //开始触摸i抬起的事件 linearlayout2.onintercepttouchevent()=false button.touch()=false button.ontouchevent()=true //触摸抬起的事件被消费 button.dispatchtouchevent()=true linearlayout2.dispatchtouchevent()=true linearlayout1.dispatchtouchevent()=true activity.dispatchtouchevent()=true 按钮被点击！ //onclick button.performclick()=true
开始测试用例：
修改代码：
eventdistributionactivity.java，将boolean dis = false;修改为boolean dis = true;
mbtn.setontouchlistener(new view.ontouchlistener() {
@override
public boolean ontouch(view v, motionevent event) {
boolean dis = true;
log.v("showlog", "button.touch()=" + dis);
return dis;
}
});
按下和松开按钮：可以看到，事件被button.touch()消费了，因为在touch()返回了true，事件没有继续传递下去，所以onclick事件没有被触发，没有生效。
linearlayout1.onintercepttouchevent()=false linearlayout2.onintercepttouchevent()=false button.touch()=true //触摸事件被消费 button.dispatchtouchevent()=true linearlayout2.dispatchtouchevent()=true linearlayout1.dispatchtouchevent()=true activity.dispatchtouchevent()=true //触摸按下事件处理完毕 linearlayout1.onintercepttouchevent()=false linearlayout2.onintercepttouchevent()=false button.touch()=true button.dispatchtouchevent()=true linearlayout2.dispatchtouchevent()=true linearlayout1.dispatchtouchevent()=true activity.dispatchtouchevent()=true
编程中我们会遇到多少挫折？表放弃，沙漠尽头必是绿洲。
原文：https://www.cnblogs.com/lanjiabin/p/12853407.html
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