android 用Handler更新UI线程之一

Handler通过接收Message 发送过来的常量值改变view状态，view调用的是invalidate()方法 触发了 onDraw()方法，在onDraw（）方法里面设置了view的移动值。

 

 

 

 

 

 

 

 

 

 

 

下面是java 代码

 

 

 

package com.hander.com;
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.os.Message;
import android.view.View;
import android.view.Window;
public class UI extends Activity {
 
protected static final int a= 1;   //常量
      Thread myRefreshThread = null;
      YouXi myBounceView = null;
      Handler myHandler = new Handler() {
           public void handleMessage(Message msg) {
                switch (msg.what) {
                     case UI.a: //接收到常量值为1的消息
                          myBounceView.invalidate();
                          break;
                }
//                super.handleMessage(msg);
           }
      };
      public void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           this.requestWindowFeature(Window.FEATURE_NO_TITLE);
           this.myBounceView = new YouXi(this);
           this.setContentView(this.myBounceView);  // 布局文件是view 对象
           new Thread(new myThread()).start();
      }
      class myThread implements Runnable {
           public void run() {   
                while (!Thread.currentThread().isInterrupted()) {                 
                     Message message = new Message();
                     message.what = UI.a;    
                     UI.this.myHandler.sendMessage(message); //发送 常量值为1的消息
                     try {
                          Thread.sleep(1000); 
                     } catch (InterruptedException e) {
                          Thread.currentThread().interrupt();
                     }
                }
           }
      }
 } 

 

view 代码

 

package com.hander.com;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.drawable.Drawable;
import android.view.View;
 public class YouXi extends View {
     float x = 40;//这里是圆心位置，也是圆运动的起始位置
       
     public YouXi(Context context) {
          super(context); 
     }
     @Override
     protected void onDraw(Canvas canvas) {  
           x+=10; //圆移动10个像素

      Paint mPaint = new Paint();
      mPaint.setAntiAlias(true);
      mPaint.setColor(Color.RED);
      canvas.drawCircle(x, 20, 20, mPaint);//画圆
     }
 }