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！