Android ListView弹性效果的实现方法

关于在Android中实现ListView的弹性效果，有很多不同的方法，网上一搜，也有很多，下面贴出在项目中经常用到的两种实现ListView弹性效果的方法（基本上拿来就可以用），供大家参考：

第一种比较简单，好容易理解，只是动态改变了ListView在Y轴上的可移动距离，代码如下：

import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.widget.ListView;
/**
* 弹性ListView。
* @author E
*/
public class FlexiListView extends ListView{
 //初始可拉动Y轴方向距离
 private static final int MAX_Y_OVERSCROLL_DISTANCE = 100;
 //上下文环境
 private Context mContext;
 //实际可上下拉动Y轴上的距离
 private int mMaxYOverscrollDistance;

public FlexiListView(Context context){
   super(context);
   mContext = context;
   initBounceListView();
 }

public FlexiListView(Context context, AttributeSet attrs) {
   super(context, attrs);
   mContext = context;
   initBounceListView();
 }

public FlexiListView(Context context, AttributeSet attrs, int defStyle) {
   super(context, attrs, defStyle);
   mContext = context;
   initBounceListView();
 }

private void initBounceListView(){
   final DisplayMetrics metrics = mContext.getResources().getDisplayMetrics();
     final float density = metrics.density;
   mMaxYOverscrollDistance = (int) (density * MAX_Y_OVERSCROLL_DISTANCE);
 }

@Override
 protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX,  
     int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent) {  
   //实现的本质就是在这里动态改变了maxOverScrollY的值
   return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, mMaxYOverscrollDistance, isTouchEvent);  
 }

}

第二种方法，结合了手势来实现ListView的弹性效果,这里可以根据手势来进行更多的扩展,代码如下:

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.ListView;
/**
* 具有弹性效果的ListView。主要是实现父类dispatchTouchEvent方法和OnGestureListener中onScroll方法。
* @author E
*/
public class FlexibleListView extends ListView implements OnGestureListener{

private Context context = null;
 private boolean outBound = false;
 private int distance;
 private int firstOut;

public FlexibleListView(Context context, AttributeSet attrs) {
   super(context, attrs);
   this.context = context;
 }

public FlexibleListView(Context context, AttributeSet attrs, int defStyle) {
   super(context, attrs, defStyle);
   this.context = context;
 }

public FlexibleListView(Context context) {
   super(context);
   this.context = context;
 }

GestureDetector lisGestureDetector = new GestureDetector(context, this);

@Override
 public boolean dispatchTouchEvent(MotionEvent event) {
   int act = event.getAction();
   if ((act == MotionEvent.ACTION_UP || act == MotionEvent.ACTION_CANCEL)
   && outBound) {
   outBound = false;
   // scroll back
   }
   if (!lisGestureDetector.onTouchEvent(event)) {
     outBound = false;
   } else {
     outBound = true;
   }
   Rect rect = new Rect();  
   getLocalVisibleRect(rect);  
   TranslateAnimation am = new TranslateAnimation( 0, 0, -rect.top, 0);  
   am.setDuration(300);  
   startAnimation(am);  
   scrollTo(0, 0);
   return super.dispatchTouchEvent(event);
 }

@Override
 public boolean onDown(MotionEvent e) {
   return false;
 }

@Override
 public void onShowPress(MotionEvent e) {
 }

@Override
 public boolean onSingleTapUp(MotionEvent e) {
   return false;
 }

@Override
 public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
     float distanceY) {
   int firstPos = getFirstVisiblePosition();
   int lastPos = getLastVisiblePosition();
   int itemCount = getCount();
   // outbound Top
   if (outBound && firstPos != 0 && lastPos != (itemCount - 1)) {
   scrollTo(0, 0);
   return false;
   }
   View firstView = getChildAt(firstPos);
   if (!outBound)
   firstOut = (int) e2.getRawY();
   if (firstView != null&& (outBound || (firstPos == 0
     && firstView.getTop() == 0 && distanceY < 0))) {
   // Record the length of each slide
   distance = firstOut - (int) e2.getRawY();
   scrollTo(0, distance / 2);
   return true;
   }
   // outbound Bottom
   return false;
 }

@Override
 public void onLongPress(MotionEvent e) {
 }

@Override
 public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
     float velocityY) {
   return false;
 }
}

以上两种常用Android ListView弹性效果的实现方法，整理出来，希望对大家有所帮助！