Android编程中ViewPage判断左右滑动方向的方法

package com.meityitian.app.views;
import android.content.Context; 
import android.support.v4.view.ViewPager; 
import android.util.AttributeSet; 
import android.util.Log; 
import com.meityitian.app.utils.Debug; 
/** 
 * 重写，添加了判定滑动方向的方法 
 * @author zxy 
 * 
 */ 
public class meityitianViewPager extends ViewPager { 
 private boolean left = false; 
 private boolean right = false; 
 private boolean isScrolling = false; 
 private int lastValue = -1; 
 private ChangeViewCallback changeViewCallback = null; 
 public meityitianViewPager(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  init(); 
 } 
 public meityitianViewPager(Context context) { 
  super(context); 
  init(); 
 } 
 /** 
  * init method . 
*/ 
 private void init() { 
  setOnPageChangeListener(listener); 
 } 
 /** 
  * listener ,to get move direction . 
*/ 
 public OnPageChangeListener listener = new OnPageChangeListener() { 
  @Override 
  public void onPageScrollStateChanged(int arg0) { 
   if (arg0 == 1) { 
    isScrolling = true; 
   } else { 
    isScrolling = false; 
   } 
   Debug.infoByTag("meityitianViewPager", 
     "meityitianViewPager onPageScrollStateChanged : arg0:" 
       + arg0); 
   if (arg0 == 2) { 
    Debug.infoByTag("meityitianViewPager", 
      "meityitianViewPager onPageScrollStateChanged direction left &＃63; " 
        + left); 
    Debug.infoByTag("meityitianViewPager", 
      "meityitianViewPager onPageScrollStateChanged direction right &＃63; " 
        + right); 
    //notify .... 
    if(changeViewCallback!=null){ 
     changeViewCallback.changeView(left, right); 
    } 
    right = left = false; 
   } 
  } 
  @Override 
  public void onPageScrolled(int arg0, float arg1, int arg2) { 
   if (isScrolling) { 
    if (lastValue > arg2) { 
     // 递减，向右侧滑动 
     right = true; 
     left = false; 
    } else if (lastValue