android实现自动滚动的Gallary控件效果

import java.util.Timer;
import java.util.TimerTask;
import android.content.Context;
import android.os.Handler;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.widget.Gallery;
public class HomeGallery extends Gallery
{
  /**
   * 这里的数值，限制了每次滚动的最大长度，图片宽度为480PX。这里设置600效果好一些。 这个值越大，滚动的长度就越大。
   * 也就是会出现一次滚动跨多个Image。这里限制长度后，每次滚动只能跨一个Image
   */
  private static final int timerAnimation = 1;
  private static final int time = 2000;
  private final Handler mHandler = new Handler()
  {
    public void handleMessage(android.os.Message msg)
    {
      switch (msg.what)
      {
      case timerAnimation:
        int position = getSelectedItemPosition();
        Log.i("msg", "position:"+position);
        if (position >= (getCount() - 1))
        {
          onKeyDown(KeyEvent.KEYCODE_DPAD_LEFT, null);
        } else
        {
          onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, null);
        }
        break;
      default:
        break;
      }
    };
  };
  private final Timer timer = new Timer();
  private final TimerTask task = new TimerTask()
  {
    public void run()
    {
      mHandler.sendEmptyMessage(timerAnimation);
    }
  };
  public HomeGallery(Context paramContext)
  {
    super(paramContext);
    timer.schedule(task, time, time);
  }
  public HomeGallery(Context paramContext, AttributeSet paramAttributeSet)
  {
    super(paramContext, paramAttributeSet);
    timer.schedule(task, time, time);
  }
  public HomeGallery(Context paramContext, AttributeSet paramAttributeSet,
      int paramInt)
  {
    super(paramContext, paramAttributeSet, paramInt);
    timer.schedule(task, time, time);
  }
  private boolean isScrollingLeft(MotionEvent paramMotionEvent1,
      MotionEvent paramMotionEvent2)
  {
    float f2 = paramMotionEvent2.getX();
    float f1 = paramMotionEvent1.getX();
    if (f2 > f1)
      return true;
    return false;
  }
  public boolean onFling(MotionEvent paramMotionEvent1,
      MotionEvent paramMotionEvent2, float paramFloat1, float paramFloat2)
  {
    int keyCode;
    if (isScrollingLeft(paramMotionEvent1, paramMotionEvent2))
    {
      keyCode = KeyEvent.KEYCODE_DPAD_LEFT;
    } else
    {
      keyCode = KeyEvent.KEYCODE_DPAD_RIGHT;
    }
    onKeyDown(keyCode, null);
    return true;
  }
  public void destroy()
  {
    timer.cancel();
  }
}