Android 定时器实现图片的变换

import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Log; import android.widget.ImageView; import android.widget.LinearLayout;  public class MainActivity extends Activity {   private LinearLayout linearlayout;    private ImageView main_imageview;    private int i = 0;    Timer timer = new Timer();    private Handler handler = new Handler()   {     @Override     public void handleMessage(Message msg)     {        Log.e("@@@", i + "");       //index=msg.what;       if (i > 6)       {         i = 0;       }       else       {         switch (i)         {         case 1:           main_imageview.setImageResource(R.drawable.loader_frame_1);           break;         case 2:           main_imageview.setImageResource(R.drawable.loader_frame_2);           break;         case 3:           main_imageview.setImageResource(R.drawable.loader_frame_3);           break;         case 4:           main_imageview.setImageResource(R.drawable.loader_frame_4);           break;         case 5:           main_imageview.setImageResource(R.drawable.loader_frame_5);           break;         case 6:           main_imageview.setImageResource(R.drawable.loader_frame_6);           break;         default:           break;         }         linearlayout.invalidate();       }       super.handleMessage(msg);     }   };    /** Called when the activity is first created. */   @Override   public void onCreate(Bundle savedInstanceState)   {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);      initView();   }    public void initView()   {     linearlayout = (LinearLayout) findViewById(R.id.background_main);     main_imageview = (ImageView) findViewById(R.id.main_imageview);      timer.scheduleAtFixedRate(new TimerTask()     {       @Override       public void run()       {         // TODO Auto-generated method stub         i++;         Message mesasge = new Message();         mesasge.what = i;         handler.sendMessage(mesasge);       }     }, 0, 500);   }    @Override   protected void onDestroy()   {     // TODO Auto-generated method stub     timer.cancel();     super.onDestroy();   } }