详解Android中自定义View的invalidate,Handler和postInvalidate

package com.yarin.android.Examples_05_01;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.KeyEvent;
import android.view.MotionEvent;

public class Activity01 extends Activity
{
 private static final int REFRESH  = 0x000001;
 
 /* 声明GameView类对象 */
 private GameView   mGameView = null;

 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);

  /* 实例化GameView对象 */
  this.mGameView = new GameView(this);

  // 设置显示为我们自定义的View(GameView)
  setContentView(mGameView);

  // 开启线程
  new Thread(new GameThread()).start();
 }

// Handler myHandler = new Handler()
// {
//  //接收到消息后处理
//  public void handleMessage(Message msg)
//  { switch (msg.what)
//   {
//   case Activity01.REFRESH:
//    mGameView.invalidate();
//    break;   }
//   super.handleMessage(msg);
//  }   
// };
//
// class GameThread implements Runnable
// { public void run()
//  {  while (!Thread.currentThread().isInterrupted())
//   { Message message = new Message();
//    message.what = Activity01.REFRESH;
//    //发送消息
//    Activity01.this.myHandler.sendMessage(message);
//    try
//    {Thread.sleep(100);
//    }
//    catch (InterruptedException e)
//    {Thread.currentThread().interrupt();
//    }
//   }
//  }
// }
// **
//  * 当然可以将GameThread类这样写
//  * 同样可以更新界面，并且不在需要
//  * Handler在接受消息
 class GameThread implements Runnable
 {
  public void run()
  {
   while (!Thread.currentThread().isInterrupted())
   {
    try
    {
     Thread.sleep(100);
    }
    catch (InterruptedException e)
    {
     Thread.currentThread().interrupt();
    }
    //使用postInvalidate可以直接在线程中更新界面
    mGameView.postInvalidate();
//    如果用invalidate()则会出错
//    mGameView.invalidate();
//    FATAL EXCEPTION: Thread-8
//     android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
//      at android.view.ViewRoot.checkThread(ViewRoot.java:2802)
//     at android.view.ViewRoot.invalidateChild(ViewRoot.java:607)
//      at android.view.ViewRoot.invalidateChildInParent(ViewRoot.java:633)
//      at android.view.ViewGroup.invalidateChild(ViewGroup.java:2505)
//      at android.view.View.invalidate(View.java:5139)
//     at com.yarin.android.Examples_05_01.Activity01$GameThread.run(Activity01.java:81)
//     at java.lang.Thread.run(Thread.java:1096)
//               查看View源文件
//    public void postInvalidate(int left, int top, int right, int bottom) {
//           postInvalidateDelayed(0, left, top, right, bottom);
//       }
//
//       public void postInvalidateDelayed(long delayMilliseconds) {
//           // We try only with the AttachInfo because there's no point in invalidating
//           // if we are not attached to our window
//           if (mAttachInfo != null) {
//               Message msg = Message.obtain();
//               msg.what = AttachInfo.INVALIDATE_MSG;
//               msg.obj = this;
//               mAttachInfo.mHandler.sendMessageDelayed(msg, delayMilliseconds);
//           }

   }
  }
 }
 
 
 //详细事件处理见第三章
 //当然这些事件也可以写在GameView中
 //触笔事件
 public boolean onTouchEvent(MotionEvent event)
 {
  return true;
 }
 
 //按键按下事件
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
     return true;
    }
   
 //按键弹起事件
 public boolean onKeyUp(int keyCode, KeyEvent event)
 {
  switch (keyCode)
  {
  //上方向键
  case KeyEvent.KEYCODE_DPAD_UP:
   mGameView.y-=3;
   break;
  //下方向键
  case KeyEvent.KEYCODE_DPAD_DOWN:
   mGameView.y+=3;
   break;
  }
  return false;
 }
 
 public boolean onKeyMultiple(int keyCode, int repeatCount, KeyEvent event)
 {
  return true;
 }
}