Android事件传递和分发机制

PS：之前写的有些地方不够清楚，配图也有点小问题，特此更正了下。2017-9-18

今天看了Android事件分发的一些资料，自己也研究了源码，了解了事件分发的流程和机制，特此记录下。
首先自定义了两个View,一个Button,一个LinearLayout,分别重写了onTouchEvent、dispatchTouchEvent、onFilterTouchEventForSecurity这三个方法。代码如下：

public class MyButton extends AppCompatButton {
    private static final String TAG = "TestTouchEventButton";
    public MyButton(Context context) {
        super(context);
    }

    public MyButton(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.i(TAG, "onTouchEvent: "+event.getAction());
//        super.onTouchEvent(event);
        return super.onTouchEvent(event);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        Log.i(TAG, "dispatchTouchEvent: "+event.getAction());
        return super.dispatchTouchEvent(event);
    }

    @Override
    public boolean onFilterTouchEventForSecurity(MotionEvent event) {
        Log.i(TAG, "onFilterTouchEventForSecurity: "+event.getAction());
        return super.onFilterTouchEventForSecurity(event);
    }

}

public class MyLayout extends LinearLayout {
    private static final String TAG = "TestTouchEventLayout";

    public MyLayout(Context context) {
        super(context);
    }

    public MyLayout(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.i(TAG, "onTouchEvent: "+event.getAction());
        return super.onTouchEvent(event);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.i(TAG, "dispatchTouchEvent: "+ev.getAction());
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onFilterTouchEventForSecurity(MotionEvent event) {
        Log.i(TAG, "onFilterTouchEventForSecurity: ");
        return super.onFilterTouchEventForSecurity(event);
    }
}
//activity 
public class TestTouchDispatchActivity extends BaseActivity {

    private static final String TAG = "TestTouchEventActivity";

    @BindView(R.id.btn)
    MyButton mBtn;


    @Override
    protected void initPresenter() {

    }

    @Override
    protected int attachLayoutRes() {
        return R.layout.activity_test_touch_dispatch;
    }

    @Override
    protected void initViews() {
        mBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.i(TAG, "onClick: ");
            }
        });

        mBtn.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.i(TAG, "onTouch: "+event.getAction());
                return false;
            }
        });
    }
}
//布局文件
<com.sleep.sunshine.view.MyLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.sleep.sunshine.view.MyButton
        android:id="@+id/btn"
        android:text="CLICK"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</com.sleep.sunshine.view.MyLayout>

一、先屏蔽掉MyLayout中的log,只看Button里面的事件分发和传递情况（PS：每项对比后直接说正确的结论，后面在从源码层面分析）：

1.onTouch方法里面返回true和false,打印log如下：

mBtn.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.i(TAG, "onTouch: "+event.getAction());
                return true/false;
            }
        });
//true
07-27 18:45:56.160 16726-16726/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 18:45:56.160 16726-16726/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
07-27 18:45:56.160 16726-16726/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 0
07-27 18:45:56.277 16726-16726/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 1
07-27 18:45:56.277 16726-16726/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 1
07-27 18:45:56.277 16726-16726/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 1
//false
07-27 18:43:04.297 14262-14262/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 18:43:04.297 14262-14262/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
07-27 18:43:04.297 14262-14262/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 0
07-27 18:43:04.297 14262-14262/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 0
07-27 18:43:04.373 14262-14262/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 1
07-27 18:43:04.373 14262-14262/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 1
07-27 18:43:04.374 14262-14262/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 1
07-27 18:43:04.374 14262-14262/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 1
07-27 18:43:04.374 14262-14262/com.sleep.sunshine I/TestTouchEventActivity: onClick: 

# 对比结论：onTouch返回true后，不会再调用onTouchEvent和onClick方法。

2.将MyButton里面的onTouchEvent方法里面返回分别返回true和false,打印log如下：

@Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.i(TAG, "onTouchEvent: "+event.getAction());
        return true/false;
    }
//true
07-27 18:51:28.626 19877-19877/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 18:51:28.626 19877-19877/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
07-27 18:51:28.626 19877-19877/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 0
07-27 18:51:28.626 19877-19877/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 0
07-27 18:51:28.665 19877-19877/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 1
07-27 18:51:28.665 19877-19877/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 1
07-27 18:51:28.665 19877-19877/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 1
07-27 18:51:28.665 19877-19877/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 1
//false
07-27 18:52:23.649 20415-20415/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 18:52:23.649 20415-20415/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
07-27 18:52:23.649 20415-20415/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 0
07-27 18:52:23.649 20415-20415/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 0

# 对比结论：a、onTouchEvent返回false，代表不再接受同组的事件（ACTION_DOWN= 0 ,ACTION_UP=1）
#b、和上面的1对比说明onClick方法是在super.onTouchEvent(event)方法里面调用的。事实证明查看源码也能发现这一点：
//父类TextView的onTouchEvent方法。
 @Override
    public boolean onTouchEvent(MotionEvent event) {
       ......
     
            final boolean textIsSelectable = isTextSelectable();
            if (touchIsFinished && mLinksClickable && mAutoLinkMask != 0 && textIsSelectable) {
                // The LinkMovementMethod which should handle taps on links has not been installed
                // on non editable text that support text selection.
                // We reproduce its behavior here to open links for these.
                ClickableSpan[] links = ((Spannable) mText).getSpans(getSelectionStart(),
                        getSelectionEnd(), ClickableSpan.class);

                if (links.length > 0) {
                    links[0].onClick(this);
                    handled = true;
                }
            }

          ......

        return superResult;
    }

3.将MyButton里面的onFilterTouchEventForSecurity方法里面返回分别返回true和false,打印log如下：

@Override
    public boolean onFilterTouchEventForSecurity(MotionEvent event) {
        Log.i(TAG, "onFilterTouchEventForSecurity: "+event.getAction());
        return true/false;
    }
//true
07-27 19:13:40.029 32428-32428/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 19:13:40.029 32428-32428/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
07-27 19:13:40.029 32428-32428/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 0
07-27 19:13:40.029 32428-32428/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 0
07-27 19:13:40.082 32428-32428/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 1
07-27 19:13:40.082 32428-32428/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 1
07-27 19:13:40.082 32428-32428/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 1
07-27 19:13:40.082 32428-32428/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 1
07-27 19:13:40.083 32428-32428/com.sleep.sunshine I/TestTouchEventActivity: onClick: 
//false
07-27 19:15:31.465 1655-1655/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 19:15:31.467 1655-1655/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0

4.将MyButton里面的dispatchTouchEvent方法里面返回分别返回true和false,打印log如下：

@Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        Log.i(TAG, "dispatchTouchEvent: "+event.getAction());
        return true/false;
    }
//true
07-27 19:19:09.215 4026-4026/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
07-27 19:19:09.264 4026-4026/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 1
//false
07-27 19:19:46.849 4676-4676/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0

#结论：View 中的dispatchTouchEvent通过开关onFilterTouchEventForSecurity（低版本的API是用的onInterceptTouchEvent）里面控制着onTouch和onTouchEvent的调用，而且可以看到当onTouch返回true的时候，就不会调用onTouchEvent方法了，证明了1中的现象。
  public boolean dispatchTouchEvent(MotionEvent event) {
       .....
        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;
            }
        }
       .....
        return result;
    }

button事件分发小节：

2428413-fc026fbb6243cad7.png

二、在有父布局Layout的情况下的事件分发直接说结论了，有兴趣的同学可以参考上面的方法去打印Log或者翻看源码。

1、不做任何改变时的log

09-18 10:09:45.327 31952-31952/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 0
09-18 10:09:45.327 31952-31952/com.sleep.sunshine I/TestTouchEventLayout: onFilterTouchEventForSecurity: 
09-18 10:09:45.327 31952-31952/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
09-18 10:09:45.327 31952-31952/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
09-18 10:09:45.327 31952-31952/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 0
09-18 10:09:45.327 31952-31952/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 0
09-18 10:09:45.392 31952-31952/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 2
09-18 10:09:45.392 31952-31952/com.sleep.sunshine I/TestTouchEventLayout: onFilterTouchEventForSecurity: 
09-18 10:09:45.392 31952-31952/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 2
09-18 10:09:45.392 31952-31952/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 2
09-18 10:09:45.392 31952-31952/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 2
09-18 10:09:45.392 31952-31952/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 2
09-18 10:09:45.396 31952-31952/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 1
09-18 10:09:45.396 31952-31952/com.sleep.sunshine I/TestTouchEventLayout: onFilterTouchEventForSecurity: 
09-18 10:09:45.396 31952-31952/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 1
09-18 10:09:45.396 31952-31952/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 1
09-18 10:09:45.396 31952-31952/com.sleep.sunshine I/TestTouchEventActivity: onTouch: 1
09-18 10:09:45.396 31952-31952/com.sleep.sunshine I/TestTouchEventButton: onTouchEvent: 1
09-18 10:09:45.397 31952-31952/com.sleep.sunshine I/TestTouchEventActivity: onClick:

2、将MyButton的onFilterTouchEventForSecurity 方法里直接返回false

@Override
    public boolean onFilterTouchEventForSecurity(MotionEvent event) {
        Log.i(TAG, "onFilterTouchEventForSecurity: "+event.getAction());
//        return super.onFilterTouchEventForSecurity(event);
        return false;
    }

09-18 10:13:33.888 1386-1386/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 0
09-18 10:13:33.888 1386-1386/com.sleep.sunshine I/TestTouchEventLayout: onFilterTouchEventForSecurity: 
09-18 10:13:33.888 1386-1386/com.sleep.sunshine I/TestTouchEventButton: dispatchTouchEvent: 0
09-18 10:13:33.888 1386-1386/com.sleep.sunshine I/TestTouchEventButton: onFilterTouchEventForSecurity: 0
09-18 10:13:33.888 1386-1386/com.sleep.sunshine I/TestTouchEventLayout: onFilterTouchEventForSecurity: 
09-18 10:13:33.889 1386-1386/com.sleep.sunshine I/TestTouchEventActivity: onTouch  layout: 0
09-18 10:13:33.889 1386-1386/com.sleep.sunshine I/TestTouchEventLayout: onTouchEvent: 0

3、将MyLayout的onFilterTouchEventForSecurity 方法里直接返回false

09-18 10:16:46.071 4555-4555/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 0
09-18 10:16:46.071 4555-4555/com.sleep.sunshine I/TestTouchEventLayout: onFilterTouchEventForSecurity:

3、将MyLayout的dispatchTouchEvent方法里返回true / false

@Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.i(TAG, "dispatchTouchEvent: "+ev.getAction());
//        return super.dispatchTouchEvent(ev);
        return true/false;
    }

//true
09-18 10:18:07.333 5480-5480/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 0
//false
09-18 10:18:07.333 5480-5480/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 0
09-18 10:18:07.362 5480-5480/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 2
09-18 10:18:07.380 5480-5480/com.sleep.sunshine I/TestTouchEventLayout: dispatchTouchEvent: 1

4、总结流程图如下：

Layout 的dispatchTouchEvent -> Layout的onFilterTouchEventForSecurity -> Button的dispatchTouchEvent -> Button的onFilterTouchEventForSecurity

2428413-74c2fff552c0e43b.png

最后编辑于：2017.12.09 02:51:58

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