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); 
   } 
  } 
 } 

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。