Android code cut 1 --圆形在屏幕撞墙弹回

package com.example.helloandroid;

import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.os.Bundle;

import android.os.Handler;

import android.view.MotionEvent;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

public class HelloAndroid extends Activity {

private TextView mTextView01;

private TextView mTextView02;

private Button mButtonView01;

private static final String url = "file:///android_asset/index.html";

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

MyView myView = new MyView(this);

//setContentView(R.layout.main);

setContentView(myView);

}

/*自定义继承View的MyView*/

private class MyView extends View implements Runnable

{

boolean isRunning = true;

int radius = 30;

int left = 30;

int top = 30;

Handler handler;

int dx=1;

int dy=1;

public MyView(Context context)

{

super(context);

handler = new Handler();

new Thread(this).start();

}

/*重写onDraw()*/

@Override

protected void onDraw(Canvas canvas)

{

super.onDraw(canvas);

canvas.drawColor(Color.WHITE);//背景色为白

Paint paint = new Paint();

paint.setAntiAlias(true);//去锯齿

paint.setColor(Color.RED);

paint.setStyle(Paint.Style.STROKE);//空心的

paint.setStrokeWidth(3);//外框宽度

/*画空心圆形*/

canvas.drawCircle(left, top, radius, paint);

}

@Override

public boolean onTouchEvent(MotionEvent event){

isRunning = false;

return true;

}

public void run() {

// TODO Auto-generated method stub

while(isRunning){

dx = left < radius || left > (getWidth()-radius)? -dx:dx;

dy = top < radius || top > (getHeight()-radius)? -dy:dy;

left = left + dx;

top = top + dy;

handler.post(new Runnable(){

public void run(){

invalidate();

}

}

);

try{

Thread.sleep(10);

}catch(InterruptedException e){

e.printStackTrace();

}

}

}

}

}