android Gallery做图片滚动，每次滑动翻一页

import android.content.Context;import android.util.AttributeSet;import android.view.KeyEvent;import android.view.MotionEvent;import android.widget.Gallery;public class GuideGallery extends Gallery {public GuideGallery(Context context) {super(context);// TODO Auto-generated constructor stub}public GuideGallery(Context context,AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stub}public GuideGallery(Context context, AttributeSet attrs,int defStyle) {super(context, attrs, defStyle);}@Overridepublic boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,float velocityY) {// TODO Auto-generated method stubint kEvent;        if(isScrollingLeft(e1, e2)){ //Check if scrolling left          kEvent = KeyEvent.KEYCODE_DPAD_LEFT;        }        else{ //Otherwise scrolling right          kEvent = KeyEvent.KEYCODE_DPAD_RIGHT;        }        onKeyDown(kEvent, null);        return true;  }private boolean isScrollingLeft(MotionEvent e1, MotionEvent e2){        return e2.getX() > e1.getX();    }}