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

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

先分享下源码：Android实现下拉刷新和上拉加载更多

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);
   }
  }
 } 

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