Android：处理触摸事件

http://blog.csdn.net/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

publicbooleanonTouchEvent（MotionEventevent）；

public boolean onTouchEvent（MotionEvent event）；

（2）为View指定触摸事件的监听器

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。

importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.view.Gravity;
importandroid.view.MotionEvent;
importandroid.view.View;
importandroid.widget.Button;
importandroid.widget.Toast;

publicclassTouchButtonActivityextendsActivity{

Buttonbutton1;
TouchListenertl;

@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

button1=(Button)findViewById(R.id.button1);
tl=newTouchListener();

button1.setOnTouchListener(tl);

}


classTouchListenerimplementsView.OnTouchListener{

privateinti=0;
@Override
publicbooleanonTouch(Viewv,MotionEventevent){
//TODOAuto-generatedmethodstub
intaction=event.getAction();

Toasttoast=Toast.makeText(getApplicationContext(),
"The"+event.toString()+"hasrecieved!",Toast.LENGTH_SHORT);
toast.setGravity(Gravity.CENTER,0,100*i);
i++;
i=i%4;
toast.show();

returnfalse;
}
}
}

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。

importandroid.content.Context;
importandroid.graphics.Canvas;
importandroid.graphics.Color;
importandroid.graphics.Paint;
importandroid.util.AttributeSet;
importandroid.view.MotionEvent;
importandroid.view.View;

publicclassDotextendsView{

privatestaticfinalfloatRADIUS=40;
privatefloatx=40;
privatefloaty=40;
privatefloatinitialX;
privatefloatinitialY;
privatefloatoffsetX;
privatefloatoffsetY;
privatePaintbackgroundPaint;
privatePaintmyPaint;

publicDot(Contextcontext,AttributeSetattrs){
super(context,attrs);

backgroundPaint=newPaint();
backgroundPaint.setColor(Color.BLUE);

myPaint=newPaint();
myPaint.setColor(Color.YELLOW);
myPaint.setAntiAlias(true);

}

@Override
publicbooleanonTouchEvent(MotionEventevent){
intaction=event.getAction();
switch(action){
caseMotionEvent.ACTION_DOWN:
initialX=x;
initialY=y;
offsetX=event.getX();
offsetY=event.getY();
break;
caseMotionEvent.ACTION_MOVE:
caseMotionEvent.ACTION_UP:
caseMotionEvent.ACTION_CANCEL:
x=initialX+event.getX()-offsetX;
y=initialY+event.getY()-offsetY;
break;
}
event.recycle();
return(true);
}
@Override
publicvoiddraw(Canvascanvas){
intwidth=canvas.getWidth();
intheight=canvas.getHeight();

canvas.drawRect(0,0,width,height,backgroundPaint);
canvas.drawCircle(x,y,RADIUS,myPaint);
invalidate();
}
}

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

<?xmlversion="1.0"encoding="utf-8"?>
<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<com.tsiannian.gmail.dot.Dot
android:id="@+id/dot"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>