您當前位置：首頁 > php開源 > 綜合技術 > Android的事件機制

Android的事件機制

來源：程序員人生發布時間：2016-11-11 08:31:08 閱讀次數：3636次

Android的事件機制

1、理論概述

最基本的操作類型：

down 手指按下
move 手指在屏幕上移動
up 手指從屏幕上離開

觸屏操作的順序：down->move->move->…->up

對屏幕的任1操作，系統都會產生1個MotionEvent對象來對應這個對象。

注：點擊和長按可以同時滿足，如果只想滿足長按，則讓長按的監聽返回true。點擊和長按時可以move。

2、相干API

1、MotionEvent：觸發事件

int ACTION_DOWN = 0 : 代表down
int ACTION_MOVE = 2 : 代表move
int ACTION_UP = 1 : 代表up
getAction() : 得到事件類型
getX() : 得到事件產生的X軸的坐標（相對當前視圖）
getRawX() : 得到事件產生的X軸的坐標（相對屏幕左頂點）
getY() : 得到事件產生的Y軸的坐標（相對當前視圖）
getRawY() : 得到事件產生的Y軸的坐標（相對屏幕左頂點）

2、Activity

boolean dispatchTouchEvent(MotionEvent event) : 分發事件
boolean onTouchEvent(MotionEvent event) : 處理事件的回調（當沒有子View消費時才調用該方法）

3、View

boolean dispatchTouchEvent(MotionEvent event) : 分發事件（沒有子view，用來決定是使用onTouchEvent還是setOnTouchListener）
boolean onTouchEvent(MotionEvent event) : 處理事件的回調方法
void setOnTouchListener(OnTouchListener listener) : 設置事件監聽器
void setOnClickListener(OnClickListener l)
void setOnLongClickListener(OnClickListener l)
void setOnCreateContextMenuListener(OnCreateContextMenuListener l) 用于創建菜單監聽

4、ViewGroup

boolean dispatchTouchEvent(MotionEvent event) : 分發事件
boolean onInterceptTouchEvent(MotionEvent event) : 攔截事件的回調方法

注：這里引入兩個概念：處理和消費
只要調用了方法就叫做處理了；
只有返回了true才叫消費了；

事件對象被系統創建后，首先會調用對應Activity的dispatchTouchEvent()進行分發；

down在分發給視圖對象的進程中要肯定消費者（onTouchEvent()返回true），如果都返回false，那事件的消費者只能是activity了。
后面的move和up都將分發給消費者（多是視圖對象，也多是消費者）
當前事件的消費者只是決定了下1個事件優先交給他處理
每一個事件都需要有1個消費者

例子：

MotionEventActivity.java

package com.cwenhui.motionevent;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

import com.cwenhui.test.R;

/**
 * Created by cwenhui on 2016.02.23
 */
public class MotionEventActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_motionevent);

        findViewById(R.id.myImageview).setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.e("MotionEventActivity", "setOnTouchListener");
                return false;
            }
        });
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.e("MotionEventActivity", "dispatchTouchEvent--"+ev.getAction());
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.e("MotionEventActivity", "onTouchEvent--"+event.getAction());
        return super.onTouchEvent(event);
    }
}

layout_motionevent.xml:

<?xml version="1.0" encoding="utf⑻"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:gravity="center"
              android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="motionEvent"/>

    <com.cwenhui.motionevent.MyImageView
        android:id="@+id/myImageview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/test"/>

</LinearLayout>

MyImageview.java

package com.cwenhui.motionevent;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.ImageView;

/**
 * Created by cwenhui on 2016.02.23
 */
public class MyImageView extends ImageView {
    public MyImageView(Context context) {
        super(context);
    }

    public MyImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        Log.e("MyImageView", "MyImageView");
    }

    public MyImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        Log.e("MyImageView", "dispatchTouchEvent--"+event.getAction());
        return super.dispatchTouchEvent(event);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.e("MyImageView", "onTouchEvent--"+event.getAction());
        return super.onTouchEvent(event)/*true*/;
    }
}

運行分析：
運行結果

如果點擊圖片并滑動，則

09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MyImageView: onTouchEvent--0
09-20 03:20:37.674 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--0
09-20 03:20:37.708 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.708 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.724 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.724 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.741 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.741 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.758 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.758 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.774 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:20:37.774 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--2
09-20 03:20:37.802 25085-25085/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 03:20:37.802 25085-25085/com.cwenhui.test E/MotionEventActivity: onTouchEvent--1

如果將MyImageview.java中的onTouchEvent(MotionEvent event)返回值改成true，則

09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.122 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--0
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.174 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.191 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.208 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.224 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MyImageView: dispatchTouchEvent--1
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 03:22:16.279 2077-2077/com.cwenhui.test E/MyImageView: onTouchEvent--1

如果此時MotionEventActivity中的OnTouchListener的onTouch()方法返回true，以下：

findViewById(R.id.myImageview).setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.e("MotionEventActivity", "setOnTouchListener--"+event.getAction());
                return true;
            }
        });

運行結果以下：

09-20 15:01:53.068 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 15:01:53.068 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 15:01:53.068 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.105 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.105 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.105 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.122 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.122 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.122 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.138 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.139 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.139 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.155 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.155 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.155 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.172 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.172 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.172 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.189 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.189 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.189 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MyImageView: dispatchTouchEvent--1
09-20 15:01:53.237 3767-3767/com.cwenhui.test E/MotionEventActivity: setOnTouchListener

可見，沒有履行MyImageview的onTouchEvent(MotionEvent event)方法了。

如果改成手指按下時返回true，即

findViewById(R.id.myImageview).setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.e("MotionEventActivity", "setOnTouchListener--"+event.getAction());
//                return false;
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    return true;
                }

                return false;
            }
        });

結果為:

09-20 16:30:48.573 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--0
09-20 16:30:48.573 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--0
09-20 16:30:48.573 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--0
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.605 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.622 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.638 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.639 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.639 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.639 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.655 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.672 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--2
09-20 16:30:48.689 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--2
09-20 16:30:48.717 16591-16591/com.cwenhui.test E/MotionEventActivity: dispatchTouchEvent--1
09-20 16:30:48.717 16591-16591/com.cwenhui.test E/MyImageView: dispatchTouchEvent--1
09-20 16:30:48.718 16591-16591/com.cwenhui.test E/MotionEventActivity: setOnTouchListener--1
09-20 16:30:48.718 16591-16591/com.cwenhui.test E/MyImageView: onTouchEvent--1