Android：处理触摸事件

 

http://blog.youkuaiyun.com/tsiannian/article/details/6624604

 

Android提供了两种常用的处理触摸事件的方式：

（1）在自定义的View对象中覆盖

view plain copy to clipboard print ?

1. public boolean onTouchEvent（MotionEvent event）；  

public boolean onTouchEvent（MotionEvent event）；

（2）为View指定触摸事件的监听器

view plain copy to clipboard print ?

1. myView.setOnTouchListener(new View.onTouchListener(View v, MotionEvent event))；  

myView.setOnTouchListener(new View.onTouchListener(View v, MotionEvent event))；

当然一个监听器可以处理多个View的触摸事件，因此多了一个View 参数。下面是一个小小的例子：我们知道一个当点击Button对象时，会调用onClickListener中的onClick函数，我们可以模拟一下这种效果。

view plain copy to clipboard print ?

1. import android.app.Activity;  
2. import android.os.Bundle;  
3. import android.view.Gravity;  
4. import android.view.MotionEvent;  
5. import android.view.View;  
6. import android.widget.Button;  
7. import android.widget.Toast;  
8.   
9. public class TouchButtonActivity extends Activity {  
10.   
11.     Button button1;  
12.     TouchListener tl;  
13.       
14.     @Override  
15.     public void onCreate(Bundle savedInstanceState) {  
16.         super.onCreate(savedInstanceState);  
17.         setContentView(R.layout.main);  
18.           
19.         button1 = (Button)findViewById(R.id.button1);  
20.         tl = new TouchListener();  
21.           
22.         button1.setOnTouchListener(tl);  
23.           
24.     }  
25.       
26.       
27.     class TouchListener implements View.OnTouchListener{  
28.           
29.         private int i = 0;  
30.         @Override  
31.         public boolean onTouch(View v, MotionEvent event) {  
32.             // TODO Auto-generated method stub   
33.             int action = event.getAction();  
34.               
35.             Toast toast = Toast.makeText(getApplicationContext(),   
36.                     "The "+ event.toString()+"has recieved!", Toast.LENGTH_SHORT);  
37.             toast.setGravity(Gravity.CENTER , 0, 100*i);  
38.             i++;  
39.             i = i%4;  
40.             toast.show();  
41.               
42.             return false;  
43.         }  
44.     }  
45. }  

import android.app.Activity; import android.os.Bundle; import android.view.Gravity; import android.view.MotionEvent; import android.view.View; import android.widget.Button; import android.widget.Toast; public class TouchButtonActivity extends Activity { Button button1; TouchListener tl; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); button1 = (Button)findViewById(R.id.button1); tl = new TouchListener(); button1.setOnTouchListener(tl); } class TouchListener implements View.OnTouchListener{ private int i = 0; @Override public boolean onTouch(View v, MotionEvent event) { // TODO Auto-generated method stub int action = event.getAction(); Toast toast = Toast.makeText(getApplicationContext(), "The "+ event.toString()+"has recieved!", Toast.LENGTH_SHORT); toast.setGravity(Gravity.CENTER , 0, 100*i); i++; i = i%4; toast.show(); return false; } } }

运行上面的代码，点击Button按钮会出现几个Toast提示框。实际上当我们点击View时，收到的是一个 事件序列。刚点击时会收到ACTION_DOWN， 触摸屏是很敏感的， 你还会收到几个ACTION_MOVE， 当手放开时会收到ACTION_UP；下面来点有意思的代码来处理不同的事件。其中手势终止时会会触发ACTION_CANCEL。

view plain copy to clipboard print ?

1. import android.content.Context;  
2. import android.graphics.Canvas;  
3. import android.graphics.Color;  
4. import android.graphics.Paint;  
5. import android.util.AttributeSet;  
6. import android.view.MotionEvent;  
7. import android.view.View;  
8.   
9. public class Dot extends View {  
10.       
11.     private static final float RADIUS = 40;  
12.     private float x = 40;  
13.     private float y = 40;  
14.     private float initialX;  
15.     private float initialY;  
16.     private float offsetX;  
17.     private float offsetY;  
18.     private Paint backgroundPaint;  
19.     private Paint myPaint;  
20.   
21.     public Dot(Context context, AttributeSet attrs) {  
22.         super(context, attrs);  
23.           
24.         backgroundPaint = new Paint();  
25.         backgroundPaint.setColor(Color.BLUE);  
26.           
27.         myPaint = new Paint();  
28.         myPaint.setColor(Color.YELLOW);  
29.         myPaint.setAntiAlias(true);  
30.           
31.     }  
32.       
33.     @Override  
34.     public boolean onTouchEvent(MotionEvent event){  
35.         int action = event.getAction();  
36.         switch(action){  
37.         case MotionEvent.ACTION_DOWN:  
38.             initialX = x;  
39.             initialY = y;  
40.             offsetX = event.getX();  
41.             offsetY = event.getY();  
42.             break;  
43.         case MotionEvent.ACTION_MOVE:  
44.         case MotionEvent.ACTION_UP:  
45.         case MotionEvent.ACTION_CANCEL:  
46.             x = initialX + event.getX() - offsetX;  
47.             y = initialY + event.getY() - offsetY;  
48.             break;  
49.         }  
50.         event.recycle();  
51.         return(true);  
52.     }  
53.      @Override  
54.      public void draw(Canvas canvas){  
55.          int width = canvas.getWidth();  
56.          int height = canvas.getHeight();  
57.            
58.          canvas.drawRect(0, 0, width, height, backgroundPaint);  
59.          canvas.drawCircle(x, y, RADIUS, myPaint);  
60.          invalidate();  
61.      }  
62. }  

import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; public class Dot extends View { private static final float RADIUS = 40; private float x = 40; private float y = 40; private float initialX; private float initialY; private float offsetX; private float offsetY; private Paint backgroundPaint; private Paint myPaint; public Dot(Context context, AttributeSet attrs) { super(context, attrs); backgroundPaint = new Paint(); backgroundPaint.setColor(Color.BLUE); myPaint = new Paint(); myPaint.setColor(Color.YELLOW); myPaint.setAntiAlias(true); } @Override public boolean onTouchEvent(MotionEvent event){ int action = event.getAction(); switch(action){ case MotionEvent.ACTION_DOWN: initialX = x; initialY = y; offsetX = event.getX(); offsetY = event.getY(); break; case MotionEvent.ACTION_MOVE: case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: x = initialX + event.getX() - offsetX; y = initialY + event.getY() - offsetY; break; } event.recycle(); return(true); } @Override public void draw(Canvas canvas){ int width = canvas.getWidth(); int height = canvas.getHeight(); canvas.drawRect(0, 0, width, height, backgroundPaint); canvas.drawCircle(x, y, RADIUS, myPaint); invalidate(); } }

下面是mian.xml

view plain copy to clipboard print ?

1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:orientation="vertical"  
4.     android:layout_width="fill_parent"  
5.     android:layout_height="fill_parent"  
6.     >  
7. <com.tsiannian.gmail.dot.Dot  
8.     android:id="@+id/dot"  
9.     android:layout_width="wrap_content"  
10.     android:layout_height="wrap_content"  
11.     />  
12. </LinearLayout>