Android(安卓)onTouchEvent和onInterceptTouchEvent事件分发详解(一)

转载请标明出处 Android源码详解目录

在讲解之前，先看一下demo

package com.example.androiddemo;import com.example.androiddemo.dispatch.LinearLayoutChild;import com.example.androiddemo.dispatch.LinearLayoutParent;import com.example.androiddemo.dispatch.TextView_Child;import com.example.androiddemo.utils.Util;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.view.Gravity;import android.view.MotionEvent;import android.view.View;import android.view.ViewGroup;import android.view.ViewGroup.LayoutParams;public class DispatchActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(initView());}private View initView() {TextView_Child mTextView_Child = new TextView_Child(this);ViewGroup.LayoutParams params0 = new LayoutParams(getWindowManager().getDefaultDisplay().getWidth() / 2, getWindowManager().getDefaultDisplay().getHeight() / 4);mTextView_Child.setLayoutParams(params0);mTextView_Child.setBackgroundColor(getResources().getColor(android.R.color.holo_orange_dark));LinearLayoutChild mLinearLayoutChild = new LinearLayoutChild(this);mLinearLayoutChild.addView(mTextView_Child);mLinearLayoutChild.setBackgroundColor(getResources().getColor(android.R.color.holo_red_dark));ViewGroup.LayoutParams params1 = new LayoutParams(LayoutParams.WRAP_CONTENT, getWindowManager().getDefaultDisplay().getHeight() / 2);mLinearLayoutChild.setLayoutParams(params1);mLinearLayoutChild.setGravity(Gravity.CENTER);LinearLayoutParent mLinearLayoutParent = new LinearLayoutParent(this);mLinearLayoutParent.addView(mLinearLayoutChild);mLinearLayoutParent.setBackgroundColor(getResources().getColor(android.R.color.holo_green_dark));mLinearLayoutParent.setGravity(Gravity.CENTER);return mLinearLayoutParent;}@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {boolean touch = super.dispatchTouchEvent(ev);Log.d("wld", "DispatchActivity_dispatchTouchEvent" + "_" + touch);Util.printEventLog("DispatchActivity", "dispatchTouchEvent", ev);return touch;}@Overridepublic boolean onTouchEvent(MotionEvent event) {boolean touch = super.onTouchEvent(event);Log.d("wld", "DispatchActivity_onTouchEvent" + "_" + touch);Util.printEventLog("DispatchActivity", "onTouchEvent", event);return touch;}}

package com.example.androiddemo.utils;import android.util.Log;import android.view.MotionEvent;public class Util {public static void printEventLog(String className, String methodName,MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:Log.d("wld", className + "_" + methodName + "_" + "ACTION_DOWN");break;case MotionEvent.ACTION_MOVE:Log.d("wld", className + "_" + methodName + "_" + "ACTION_MOVE");break;case MotionEvent.ACTION_UP:Log.d("wld", className + "_" + methodName + "_" + "ACTION_UP");break;case MotionEvent.ACTION_CANCEL:Log.d("wld", className + "_" + methodName + "_" + "ACTION_CANCEL");break;default:break;}}}

package com.example.androiddemo.dispatch;import com.example.androiddemo.utils.Util;import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.widget.LinearLayout;public class LinearLayoutParent extends LinearLayout {public LinearLayoutParent(Context context) {super(context);}public LinearLayoutParent(Context context, AttributeSet attrs) {super(context, attrs);}public LinearLayoutParent(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);}@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {boolean touch = super.dispatchTouchEvent(ev);Log.d("wld", "LinearLayoutParent_dispatchTouchEvent" + "_" + touch);Util.printEventLog("LinearLayoutParent", "dispatchTouchEvent", ev);return touch;}@Overridepublic boolean onTouchEvent(MotionEvent event) {boolean touch = super.onTouchEvent(event);Log.d("wld", "LinearLayoutParent_onTouchEvent" + "_" + touch);Util.printEventLog("LinearLayoutParent", "onTouchEvent", event);return touch;}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {boolean touch = super.onInterceptTouchEvent(ev);Log.d("wld", "LinearLayoutParent_onInterceptTouchEvent" + "_" + touch);Util.printEventLog("LinearLayoutParent", "onInterceptTouchEvent", ev);return touch;}}

package com.example.androiddemo.dispatch;import com.example.androiddemo.utils.Util;import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.widget.LinearLayout;public class LinearLayoutChild extends LinearLayout {public LinearLayoutChild(Context context) {super(context);}public LinearLayoutChild(Context context, AttributeSet attrs) {super(context, attrs);}public LinearLayoutChild(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);}@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {boolean touch = super.dispatchTouchEvent(ev);Log.d("wld", "LinearLayoutChild_dispatchTouchEvent" + "_" + touch);Util.printEventLog("LinearLayoutChild", "dispatchTouchEvent", ev);return touch;}@Overridepublic boolean onTouchEvent(MotionEvent event) {boolean touch = super.onTouchEvent(event);Log.d("wld", "LinearLayoutChild_onTouchEvent" + "_" + touch);Util.printEventLog("LinearLayoutChild", "onTouchEvent", event);return touch;}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {boolean touch = super.onInterceptTouchEvent(ev);Log.d("wld", "LinearLayoutChild_onInterceptTouchEvent" + "_" + touch);Util.printEventLog("LinearLayoutChild", "onInterceptTouchEvent", ev);return touch;}}

package com.example.androiddemo.dispatch;import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.widget.ImageButton;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.TextView;import com.example.androiddemo.utils.Util;public class TextView_Child extends TextView {public TextView_Child(Context context) {super(context);}public TextView_Child(Context context, AttributeSet attrs) {super(context, attrs);}public TextView_Child(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);}@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {boolean touch = super.dispatchTouchEvent(ev);Log.d("wld", "TextViewChild_dispatchTouchEvent" + "_" + touch);Util.printEventLog("TextViewChild", "dispatchTouchEvent", ev);return touch;}@Overridepublic boolean onTouchEvent(MotionEvent event) {boolean touch = super.onTouchEvent(event);Log.d("wld", "TextViewChild_onTouchEvent" + "_" + touch);Util.printEventLog("TextViewChild", "onTouchEvent", event);return touch;}}

上面所有的返回值都是默认的，我们来看一下运行结果

我们点击中间的橘色，再来看一下打印的log

我们看到，默认情况下，全部返回false，并且DispatchActivity的onTouchEvent方法执行了DOWN,MOVE,UP方法，也就说是默认情况下，事件全部被DispatchActivity的onTouchEvent方法给处理了。上面仅仅是一个演示，其实用处并不是很大，只是作为一个了解，但对我们研究Android的事件分发机制有一定的意义，因为我们如果拦截或者处理事件机制的时候一般是在View及其子类中处理。接下来我们会把DispatchActivity中的两个方法dispatchTouchEvent和onTouchEvent注释掉，我们只研究View及其子类中的Event方法。我们知道除了Button及其ImageButton的onTouchEvent方法默认返回true以外，其他的都是返回false，因为Button和ImageButton默认情况下是消耗事件的，刚才上面我们看到TextView的onTouchEvent方法默认情况下返回的是false，就是事件没有被他消耗掉，下面我们把TextView换成Button在看一看，

public class TextView_Child extends Button {

顺便注释掉DispatchActivity中的dispatchTouchEvent和onTouchEvent方法，我们看一下log

我们可以看到默认情况下Button的onTouchEvent返回的是true，因为点击的时候事件默认被他消耗掉了。好了，这里只是给大家简单的开个头，接下来就会为大家讲解一下View事件的拦截及分发机制，最后在给大家分析源码。

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