android事件分发机制学习1

1.介绍

我们定义MyButton继承Button

package com.miyapay.cspm.test01.view;import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.widget.Button;/** * Created by miya96 on 2016/12/2. */public class MyButton extends Button {    private static final String TAG = MyButton.class.getSimpleName();    public MyButton(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        int action = event.getAction();        switch (action) {            case MotionEvent.ACTION_DOWN:                Log.e(TAG, "onTouchEvent ACTION_DOWN");                break;            case MotionEvent.ACTION_MOVE:                Log.e(TAG, "onTouchEvent ACTION_MOVE");                break;            case MotionEvent.ACTION_UP:                Log.e(TAG, "onTouchEvent ACTION_UP");                break;            default:                break;        }        return super.onTouchEvent(event);    }    @Override    public boolean dispatchTouchEvent(MotionEvent event) {        int action = event.getAction();        switch (action) {            case MotionEvent.ACTION_DOWN:                Log.e(TAG, "dispatchTouchEvent ACTION_DOWN");                break;            case MotionEvent.ACTION_MOVE:                Log.e(TAG, "dispatchTouchEvent ACTION_MOVE");                break;            case MotionEvent.ACTION_UP:                Log.e(TAG, "dispatchTouchEvent ACTION_UP");                break;            default:                break;        }        return super.dispatchTouchEvent(event);    }}

在onTouchEvent和dispatchTouchEvent中打印了日志

我们加入到主布局

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"                                             android:layout_width="match_parent"                                             android:layout_height="match_parent"                                             android:orientation="vertical">    <com.miyapay.cspm.test01.view.MyButton        android:id="@+id/mybutton"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentTop="true"        android:layout_centerHorizontal="true"        android:layout_gravity="center_horizontal"        android:layout_marginTop="106dp"        android:text="@string/button"/></RelativeLayout>

MyButtonActivity代码

package com.miyapay.cspm.test01;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.view.MotionEvent;import android.view.View;import com.miyapay.cspm.test01.view.MyButton;/** * Created by miya96 on 2016/12/2. */public class MyButtonActivity extends Activity {    protected static final String TAG = "MyButton";    private MyButton mMyButton;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.button_activity);        mMyButton = (MyButton) findViewById(R.id.mybutton);        mMyButton.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                int action = event.getAction();                switch (action)                {                    case MotionEvent.ACTION_DOWN:                        Log.e(TAG, "onTouch ACTION_DOWN");                        break;                    case MotionEvent.ACTION_MOVE:                        Log.e(TAG, "onTouch ACTION_MOVE");                        break;                    case MotionEvent.ACTION_UP:                        Log.e(TAG, "onTouch ACTION_UP");                        break;                    default:                        break;                }                return false;            }        });    }}

点击按钮

12-05 16:22:16.985 21852-21852/com.miyapay.cspm.test01 E/MyButton: dispatchTouchEvent ACTION_DOWN12-05 16:22:16.985 21852-21852/com.miyapay.cspm.test01 E/MyButton: onTouch ACTION_DOWN12-05 16:22:16.985 21852-21852/com.miyapay.cspm.test01 E/MyButton: onTouchEvent ACTION_DOWN12-05 16:22:17.056 21852-21852/com.miyapay.cspm.test01 E/MyButton: dispatchTouchEvent ACTION_MOVE12-05 16:22:17.057 21852-21852/com.miyapay.cspm.test01 E/MyButton: onTouch ACTION_MOVE12-05 16:22:17.057 21852-21852/com.miyapay.cspm.test01 E/MyButton: onTouchEvent ACTION_MOVE12-05 16:22:17.080 21852-21852/com.miyapay.cspm.test01 E/MyButton: dispatchTouchEvent ACTION_UP12-05 16:22:17.080 21852-21852/com.miyapay.cspm.test01 E/MyButton: onTouch ACTION_UP12-05 16:22:17.081 21852-21852/com.miyapay.cspm.test01 E/MyButton: onTouchEvent ACTION_UP

结果:
不论down、move、up
执行的顺序:
1.dispatchTouchEvent
2.setOntouchListenter的ontouch
3.onTouchEvent

源码探索

2.dispatchTouchEvent的源码

public boolean dispatchTouchEvent(MotionEvent event) {    if (mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED &&            mOnTouchListener.onTouch(this, event)) {        return true;    }    return onTouchEvent(event);}

1.首先进行了一个判断mOnTouchListener != null,(mViewFlags & ENABLED_MASK) == ENABLED以及mOnTouchListener.onTouch(this, event)三个条件为真,返回true,否则就执行onTouchEvent(event)方法并返回.

• 1.先看第一个条件

public void setOnTouchListener(OnTouchListener l) {    mOnTouchListener = l;}

当我们给控件注册ontouch事件,mOnTouchListener 已经被赋值了

• 2.第二个条件(mViewFlags & ENABLED_MASK) == ENABLED是判断当前点击的控件是否是enable的，按钮默认都是enable的，因此这个条件恒定为true。
• 3.mOnTouchListener.onTouch(this, event),如果ontouch方法返回true,那么三个条件全部成立,整个方法返回true,如果我们在ontouch返回false

因此:首先在dispatchTouchEvent执行的事onTouch方法,因此ontouch肯定要优先于onClick方法,如果ontouch返回true,而dispatchTouchEvent返回true,不会继续执行.结果打印也证实了,如果ontouch返回true,onclick不会执行.

onTouchEvent

view的onTouchEvent分析

/**     * Implement this method to handle touch screen motion events.     *     * @param event The motion event.     * @return True if the event was handled, false otherwise.     */    public boolean onTouchEvent(MotionEvent event) {        final int viewFlags = mViewFlags;        if ((viewFlags & ENABLED_MASK) == DISABLED) {            // A disabled view that is clickable still consumes the touch            // events, it just doesn't respond to them.            return (((viewFlags & CLICKABLE) == CLICKABLE ||                    (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE));        }        if (mTouchDelegate != null) {            if (mTouchDelegate.onTouchEvent(event)) {                return true;            }        }        if (((viewFlags & CLICKABLE) == CLICKABLE ||                (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {            switch (event.getAction()) {                case MotionEvent.ACTION_UP:                    boolean prepressed = (mPrivateFlags & PREPRESSED) != 0;                    if ((mPrivateFlags & PRESSED) != 0 || prepressed) {                        // take focus if we don't have it already and we should in                        // touch mode.                        boolean focusTaken = false;                        if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {                            focusTaken = requestFocus();                        }                        if (!mHasPerformedLongPress) {                            // This is a tap, so remove the longpress check                            removeLongPressCallback();                            // Only perform take click actions if we were in the pressed state                            if (!focusTaken) {                                // Use a Runnable and post this rather than calling                                // performClick directly. This lets other visual state                                // of the view update before click actions start.                                if (mPerformClick == null) {                                    mPerformClick = new PerformClick();                                }                                if (!post(mPerformClick)) {                                    performClick();                                }                            }                        }                        if (mUnsetPressedState == null) {                            mUnsetPressedState = new UnsetPressedState();                        }                        if (prepressed) {                            mPrivateFlags |= PRESSED;                            refreshDrawableState();                            postDelayed(mUnsetPressedState,                                    ViewConfiguration.getPressedStateDuration());                        } else if (!post(mUnsetPressedState)) {                            // If the post failed, unpress right now                            mUnsetPressedState.run();                        }                        removeTapCallback();                    }                    break;                case MotionEvent.ACTION_DOWN:                    if (mPendingCheckForTap == null) {                        mPendingCheckForTap = new CheckForTap();                    }                    mPrivateFlags |= PREPRESSED;                    mHasPerformedLongPress = false;                    postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());                    break;                case MotionEvent.ACTION_CANCEL:                    mPrivateFlags &= ~PRESSED;                    refreshDrawableState();                    removeTapCallback();                    break;                case MotionEvent.ACTION_MOVE:                    final int x = (int) event.getX();                    final int y = (int) event.getY();                    // Be lenient about moving outside of buttons                    int slop = mTouchSlop;                    if ((x < 0 - slop) || (x >= getWidth() + slop) ||                            (y < 0 - slop) || (y >= getHeight() + slop)) {                        // Outside button                        removeTapCallback();                        if ((mPrivateFlags & PRESSED) != 0) {                            // Remove any future long press/tap checks                            removeLongPressCallback();                            // Need to switch from pressed to not pressed                            mPrivateFlags &= ~PRESSED;                            refreshDrawableState();                        }                    }                    break;            }            return true;        }        return false;    }

如果控件可以点击,进入到switch语句中,如果当前是抬起手指,则会进入到MotionEvent.ACTION_UP,经过判断会执行到performClick();方法

public boolean performClick() {    sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);    if (mOnClickListener != null) {        playSoundEffect(SoundEffectConstants.CLICK);        mOnClickListener.onClick(this);        return true;    }    return false;}

只要mOnClickListener不是null,就会调用它的onclick方法,赋值在:

public void setOnClickListener(OnClickListener l) {    if (!isClickable()) {        setClickable(true);    }    mOnClickListener = l;}

总结

1.整个view事件转发流程

view.dispatchTouchEvent -> View.setOnclickListener ->View.onTouchEvent
在dispatchTouchEvent 中进行OnTouchListener判断,如果不为空,则返回true,表示消费掉，不执行ontouchevent。否则为false,执行ontouchevent。