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

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1. publicbooleanonTouchEvent（MotionEventevent）；

public boolean onTouchEvent（MotionEvent event）；

（2）为View指定触摸事件的监听器

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1. myView.setOnTouchListener(newView.onTouchListener(Viewv,MotionEventevent))；

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。

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1. importandroid.app.Activity;
2. importandroid.os.Bundle;
3. importandroid.view.Gravity;
4. importandroid.view.MotionEvent;
5. importandroid.view.View;
6. importandroid.widget.Button;
7. importandroid.widget.Toast;
9. publicclassTouchButtonActivityextendsActivity{
11. Buttonbutton1;
12. TouchListenertl;
14. @Override
15. publicvoidonCreate(BundlesavedInstanceState){
16. super.onCreate(savedInstanceState);
17. setContentView(R.layout.main);
19. button1=(Button)findViewById(R.id.button1);
20. tl=newTouchListener();
22. button1.setOnTouchListener(tl);
24. }
27. classTouchListenerimplementsView.OnTouchListener{
29. privateinti=0;
30. @Override
31. publicbooleanonTouch(Viewv,MotionEventevent){
32. //TODOAuto-generatedmethodstub
33. intaction=event.getAction();
35. Toasttoast=Toast.makeText(getApplicationContext(),
36. "The"+event.toString()+"hasrecieved!",Toast.LENGTH_SHORT);
37. toast.setGravity(Gravity.CENTER,0,100*i);
38. i++;
39. i=i%4;
40. toast.show();
42. returnfalse;
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。

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1. importandroid.content.Context;
2. importandroid.graphics.Canvas;
3. importandroid.graphics.Color;
4. importandroid.graphics.Paint;
5. importandroid.util.AttributeSet;
6. importandroid.view.MotionEvent;
7. importandroid.view.View;
9. publicclassDotextendsView{
11. privatestaticfinalfloatRADIUS=40;
12. privatefloatx=40;
13. privatefloaty=40;
14. privatefloatinitialX;
15. privatefloatinitialY;
16. privatefloatoffsetX;
17. privatefloatoffsetY;
18. privatePaintbackgroundPaint;
19. privatePaintmyPaint;
21. publicDot(Contextcontext,AttributeSetattrs){
22. super(context,attrs);
24. backgroundPaint=newPaint();
25. backgroundPaint.setColor(Color.BLUE);
27. myPaint=newPaint();
28. myPaint.setColor(Color.YELLOW);
29. myPaint.setAntiAlias(true);
31. }
33. @Override
34. publicbooleanonTouchEvent(MotionEventevent){
35. intaction=event.getAction();
36. switch(action){
37. caseMotionEvent.ACTION_DOWN:
38. initialX=x;
39. initialY=y;
40. offsetX=event.getX();
41. offsetY=event.getY();
42. break;
43. caseMotionEvent.ACTION_MOVE:
44. caseMotionEvent.ACTION_UP:
45. caseMotionEvent.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. publicvoiddraw(Canvascanvas){
55. intwidth=canvas.getWidth();
56. intheight=canvas.getHeight();
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

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1. <?xmlversion="1.0"encoding="utf-8"?>
2. <LinearLayoutxmlns: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>