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Android控件PullRefreshViewGroup实现下拉刷新和上拉加载

 更新时间：2021年06月23日 15:30:16   作者：laozhong110  
这篇文章主要为大家详细介绍了Android控件PullRefreshViewGroup实现下拉刷新和上拉加载效果，具有一定的参考价值，感兴趣的小伙伴们可以参考一下

本文实例为大家分享了Android实现下拉刷新和上拉加载更多的具体代码，供大家参考，具体内容如下

实现思路：由PullRefreshViewGroup控件来接管标准控件(比如RecyclerView、ListView等)的滑动，调用标准控件的内部方法进行短距离滑动，不再由标准控件自己来处理事件，而完全由PullRefreshViewGroup控件来处理触摸事件。标准控件内部的滑动距离等属性，通过反射获得computeVerticalScrollExtent、computeVerticalScrollRange、computeVerticalScrollOffset这三个方法来获得。

PullRefreshViewGroup控件的布局如下

部分代码实现

触摸滑动事件处理

@Override 
 public boolean onInterceptTouchEvent(MotionEvent ev) { 
  boolean bret = false; 
  switch (ev.getAction()) { 
   case MotionEvent.ACTION_DOWN: { 
    mPreY = ev.getY(); 
    Log.d(TAG, "mPreY:" + String.valueOf(mPreY)); 
   } 
   break; 
   case MotionEvent.ACTION_MOVE: { 
    float curY = ev.getY(); 
    float distance = curY - mPreY; 
    if (Math.abs(distance) >= mTouchSlop) { 
     mSliding = bret = true; 
 
     //修正第一次滑动的卡顿 
     if (distance > 0) { 
      mPreY += mTouchSlop; 
     } else { 
      mPreY -= mTouchSlop; 
     } 
 
     if (!mScroller.isFinished()) { 
      mScroller.abortAnimation(); 
     } 
    } else { 
     mSliding = bret = false; 
    } 
   } 
   break; 
   case MotionEvent.ACTION_UP: 
   case MotionEvent.ACTION_CANCEL: { 
    bret = mSliding; 
   } 
   break; 
  } 
  return bret ? true : super.onInterceptTouchEvent(ev); 
 } 
 
 @Override 
 public boolean onTouchEvent(MotionEvent event) { 
  boolean bret = false; 
 
  vTracker.addMovement(event); 
 
  switch (event.getAction()) { 
   case MotionEvent.ACTION_DOWN: { 
    mPreY = event.getY(); 
    bret = true; 
   } 
   break; 
   case MotionEvent.ACTION_MOVE: { 
    float curY = event.getY(); 
    float distance = curY - mPreY; 
    Log.d(TAG, "mPreY:" + String.valueOf(mPreY) + " distance:" + String.valueOf(distance)); 
    if (distance != 0) { 
     bret = true; 
 
     if (mSrcHeightHead == -1 && mHasPullRefresh) { 
      View child0View = mHeadView; 
      mSrcHeightHead = child0View.getHeight(); 
     } 
 
     scrollBy(distance); 
    } 
 
    mPreY = curY; 
   } 
   break; 
   case MotionEvent.ACTION_UP: 
   case MotionEvent.ACTION_CANCEL: { 
    mPreCurY = 0; 
 
    View child0View = mHeadView; 
    int child0Height = null != child0View ? child0View.getHeight() : 0; 
    int child0Height2 = null != child0View ? child0View.getLayoutParams().height : 0; //视图的最终高度是有这个来决定的,请看onMeasure 函数的实现 
    // int child0Height3 = child0View.getMeasuredHeight(); 
    if (child0Height2 != child0Height) { 
     child0Height = child0Height2; 
    } 
    int child0Top = null != child0View ? child0View.getTop() : 0; 
    int dy = child0Height - mSrcHeightHead + (mSrcHeightHead - Math.abs(child0Top)); 
    Log.d(TAG, "onTouchEvent()ACTION_UP child0Height:" + String.valueOf(child0Height) + " mSrcHeightHead:" + String.valueOf(mSrcHeightHead) + " child0Top:" + String.valueOf(child0Top)); 
    if (dy > 0) {//恢复拉伸视图的位置 
     if (!mLoadingMore && dy > mCanRefreshHeight && child0Top + child0Height2 > mCanRefreshHeight && mRefreshLoad != null) { 
      dy -= mCanRefreshHeight; 
 
      if (!mPullRefreshLoading) { 
       mPullRefreshLoading = true; 
       mTvRefreshInfo.setText("正在加载..."); 
       mRefreshLoad.pullRefreshStartLoad(); 
      } 
     } 
     mScroller.startScroll(0, 0, 0, -dy); 
     invalidate(); 
    } else { 
     vTracker.computeCurrentVelocity(1000); 
 
     float yvel = vTracker.getYVelocity(); 
     if (yvel != 0) {//为了满足内部视图的快速滚动( 中间内容视图 ) 
      mScroller.fling(0, 0, 0, (int) yvel, 0, 0, Integer.MIN_VALUE, Integer.MAX_VALUE); 
      invalidate(); 
     } 
    } 
 
    vTracker.clear(); 
    bret = true; 
   } 
   break; 
  } 
  return bret ? true : super.onTouchEvent(event); 
 }

小距离滑动代码

private void scrollBy(float distance) { 
  View child0View = mHeadView; 
  View child1View = getChildAt(null == mHeadView ? 0 : 1); 
  float distanceRemain = 0; 
 
  int child0Top = null != child0View ? child0View.getTop() : 0; 
  // int child0Height = child0View.getHeight(); 
 
  if (distance < 0) {//向上 
   int child1Top = child1View.getTop(); 
   // int child1Height = child1View.getHeight(); 
 
   //child0View 缩小 
   if (-1 != mSrcHeightHead && null != child0View && child0View.getHeight() > mSrcHeightHead) { 
    float off = distance; 
    if (child0View.getHeight() + distance < mSrcHeightHead) { 
     off = -(child0View.getHeight() - mSrcHeightHead); 
     distance -= off; 
    } else { 
     distance = 0; 
    } 
 
    child0View.getLayoutParams().height += (int) off; 
    child1Top += (int) off; //child0view 缩小的同时, child1view 的高度也会随之上升 这里很重要 
    requestLayout(); 
    child1View.offsetTopAndBottom((int) off); 
    if (null != mTailView) { 
     mTailView.offsetTopAndBottom((int) off); 
    } 
   } 
 
   if (distance != 0) { 
    if (child0Top + mSrcHeightHead + distance <= 0) { 
     distanceRemain = -(distance + (child0Top + mSrcHeightHead));//正数 
     distance = -(child0Top + mSrcHeightHead);//负数 
    } 
 
    //可以显示加载更多吗? 
    boolean bDirectDown = false; 
    boolean bCanScroll = child1View.canScrollVertically(1) || child1View.canScrollVertically(-1); 
    if (!bCanScroll) { 
     int child1ChildCount = 0; 
     if (child1View instanceof ViewGroup) { 
      child1ChildCount = ((ViewGroup) child1View).getChildCount(); 
     } 
     if (child1ChildCount > 0) { 
      ViewGroup viewGroupChild1 = (ViewGroup) child1View; 
 
      View child1LastItem = viewGroupChild1.getChildAt(child1ChildCount - 1); 
      int child1ViewBottom = viewGroupChild1.getBottom(); 
      int child1LastItemBottom = child1LastItem.getBottom() + child1Top; //相对于 ImageScaleViewGroup 的位置 
      //增加 child1ViewBottom > getHeight() 来控制 ScrollView 
      if (child1LastItemBottom == getHeight()) { 
       bDirectDown = true; 
      } 
     } 
    } 
    //正在下拉刷新的时候,不能显示加载更多 
    if ((bCanScroll || bDirectDown) && null != mTailView && !mPullRefreshLoading) { 
 
     int nVerticalScrollExtent = 0, nVerticalScrollRange = 0, nVerticalScrollOffset = 0; 
     Class c = null; 
 
     try { 
      c = Class.forName(child1View.getClass().getName()); 
     } catch (Exception ex) { 
 
     } 
     try { 
      if (null == mComputeVerticalScrollExtent) { 
       Method computeVerticalScrollExtent = findcomputeVerticalMethod(c, "computeVerticalScrollExtent"); 
       computeVerticalScrollExtent.setAccessible(true); 
       mComputeVerticalScrollExtent = computeVerticalScrollExtent; 
      } 
      nVerticalScrollExtent = (int) mComputeVerticalScrollExtent.invoke(child1View); 
     } catch (Exception ex) { 
 
     } 
     try { 
      if (null == mComputeVerticalScrollRange) { 
       Method computeVerticalScrollRange = findcomputeVerticalMethod(c, "computeVerticalScrollRange"); 
       computeVerticalScrollRange.setAccessible(true); 
       mComputeVerticalScrollRange = computeVerticalScrollRange; 
      } 
 
      nVerticalScrollRange = (int) mComputeVerticalScrollRange.invoke(child1View); 
     } catch (Exception ex) { 
 
     } 
     try { 
      if (null == mComputeVerticalScrollOffset) { 
       Method computeVerticalScrollOffset = findcomputeVerticalMethod(c, "computeVerticalScrollOffset"); 
       computeVerticalScrollOffset.setAccessible(true); 
       mComputeVerticalScrollOffset = computeVerticalScrollOffset; 
      } 
      nVerticalScrollOffset = (int) mComputeVerticalScrollOffset.invoke(child1View); 
     } catch (Exception ex) { 
 
     } 
 
 
     int range = nVerticalScrollRange - nVerticalScrollExtent; 
     if (nVerticalScrollOffset + distanceRemain > range) { 
      float nOff = distanceRemain - (range - nVerticalScrollOffset); 
 
      distanceRemain = range - nVerticalScrollOffset; 
      distance -= nOff; 
     } 
 
     int child3Bottom = mTailView.getBottom(); 
 
     if (child3Bottom + distance < getHeight()) { 
      distance = getHeight() - child3Bottom; 
     } 
    } 
 
    if (!bCanScroll) { 
     distanceRemain = 0; 
    } 
   } 
 
  } else {//向下 
   int nScrollOffset = 0; 
   try { 
    Class c = Class.forName(child1View.getClass().getName()); 
    Method computeVerticalScrollOffset = findcomputeVerticalMethod(c, "computeVerticalScrollOffset");//c.getDeclaredMethod("computeVerticalScrollOffset"); 
    computeVerticalScrollOffset.setAccessible(true); 
    nScrollOffset = (int) computeVerticalScrollOffset.invoke(child1View); 
   } catch (Exception ex) { 
 
   } 
 
   int child2Top = null != mTailView ? mTailView.getTop() : getHeight();//注意默认值 
   if (child2Top < getHeight()) { 
    if (child2Top + distance > getHeight()) { 
     distanceRemain = distance - (getHeight() - child2Top); 
     distance = getHeight() - child2Top; 
    } 
   } else if (nScrollOffset > 0) {//内部有滚动,那么就要计算内部滚动距离,其他分配给整体滚动 
    if (nScrollOffset - distance <= 0) { 
     distanceRemain = -nScrollOffset; 
     // distance = distance - nScrollOffset; 
     distance = 0; //内部能滚动,不让外部去滚动 
     if (!mScroller.isFinished()) { 
      mScroller.abortAnimation(); //内部滚动完后,立即停止 
     } 
    } else { 
     distanceRemain = -distance;//负数 
     distance = 0; 
    } 
   } else { 
    if (child0Top + distance > 0) {//child0放大,child1移动 
     int off = (int) (child0Top + distance); 
     distance = -child0Top; 
 
     if (null != child0View) { 
      child0View.getLayoutParams().height += off; 
      requestLayout(); 
     } else { 
      off = 0; 
     } 
 
     child1View.offsetTopAndBottom(off); 
     if (null != mTailView) { 
      mTailView.offsetTopAndBottom(off); 
     } 
    } 
   } 
  } 
 
  if (0 != (int) distance) { 
   if (null != child0View) { 
    child0View.offsetTopAndBottom((int) distance); 
   } 
   child1View.offsetTopAndBottom((int) distance); 
   if (null != mTailView) { 
    mTailView.offsetTopAndBottom((int) distance); 
   } 
 
   requestLayout();//奇酷360这里必须调用, 否则显示有点问题 
  } 
 
  scrollByForMidView(distanceRemain);//外部无法滚动的时候,内部滚动 
 
  if (!mPullRefreshLoading && !mLoadingMore) { 
   int tailviewTop = null != mTailView ? mTailView.getTop() : getHeight();//注意默认值 
 
   if (tailviewTop < getHeight() && mHasLoadMore) {//加载更多 
    mLoadingMore = true; 
    if (mRefreshLoad != null) { 
     mRefreshLoad.pullUpStartLoadMore(); 
    } 
   } else { 
    if (mHasPullRefresh) { 
     if (distance < 0) { 
      int child0Bottom = child0View.getBottom(); 
      if (child0Bottom < mCanRefreshHeight) { 
       mTvRefreshInfo.setText("下拉刷新"); 
      } 
     } else { 
      int child0Bottom = child0View.getBottom(); 
      if (child0Bottom > mCanRefreshHeight) { 
       mTvRefreshInfo.setText("松开刷新"); 
      } 
     } 
    } 
   } 
  } 
 }

处理标准控件小距离滚动代码，这里ListView有点特殊。

private void scrollByForMidView(float distanceRemain) { 
  if (0 != (int) distanceRemain) { 
   View child1View = getChildAt(null == mHeadView ? 0 : 1); 
   if (child1View instanceof ListView) { 
    ((ListView) child1View).smoothScrollBy((int) distanceRemain, 0); 
   } /*else if (child1View instanceof ScrollView){ 
    ((ScrollView) child1View).smoothScrollBy(0,(int) distanceRemain); 
   }*/ else { 
    child1View.scrollBy(0, (int) distanceRemain); 
   } 
  } 
 }

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。

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