Android 根据手势顶部View自动展示与隐藏效果

首先来看一下效果：

 

 大体思路如下：

总体布局用了一个自定义的viewgroup，里面包了两个view（top view，bottomview）

我在bottomview里放了viewpager，里面又有fragment，fragment里放的是listview

原理：

viewgroup在分发touchevent的时候先通过手势gesturedetector判断手势方向，当向上滑动的时候让topview和bottomview同时向上移动，反之亦然。

整体思路不是很难如下是干货：

布局文件

<com.lin.gesturedetector.myviewgroup
  android:id="@+id/view_group"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
  <include
   android:id="@+id/group_top"
   layout="@layout/view_top" />
  <include
   android:id="@+id/group_bottom"
   layout="@layout/view_bottom" />
 </com.lin.gesturedetector.myviewgroup>

手势监听重要的是打log看一下上下滑动是数值的变化，找到其规律：           

 @override
   public boolean onscroll(motionevent e1, motionevent e2, float distancex, float distancey) {
    log.i(tag, "onscroll -> distancey" + distancey);
    if (distancey < 0) {// 手势向下滑动是负值
     animatorlayoutoffset(1);
    }
    if (distancey > 0) {
     animatorlayoutoffset(0f);
    }
    return true;
   }

一定记得在viewgroup内查找控件需要在onfinishinflate后才能找到：   

 @override
 protected void onfinishinflate() {
  super.onfinishinflate();
  viewtop = findviewbyid(r.id.group_top);
  viewbottom = findviewbyid(r.id.group_bottom);
 }

在viewgroup布局的逻辑中需要处理的有一下几点：

1、onmeasure的时候要把子控件测量出来

2、onlayout时需要手动将子控件布局

接下来就是监听手势设置动画，不停的onlayout以达到topview和bottomview的布局效果  

@override
 protected void onmeasure(int widthmeasurespec, int heightmeasurespec) {
  int width = measurespec.getsize(widthmeasurespec);
  int height = measurespec.getsize(heightmeasurespec);
  viewtop.measure(measurespec.makemeasurespec(width, measurespec.exactly), measurespec.makemeasurespec(height, measurespec.at_most));
  viewbottom.measure(measurespec.makemeasurespec(width, measurespec.exactly), measurespec.makemeasurespec(height, measurespec.exactly));
  setmeasureddimension(width, height);
 }
 @override
 protected void onlayout(boolean changed, int l, int t, int r, int b) {
  int topheight = viewtop.getmeasuredheight();
  float offset = layoutoffset * topheight;
  int width = r - l;
  float topviewytop = offset - topheight;
  float topviewybottom = topviewytop + topheight;
  viewtop.layout(0, (int) topviewytop, width, (int) topviewybottom);
  viewbottom.layout(0, (int) topviewybottom, width, (int) topviewybottom + viewbottom.getmeasuredheight());
 }
 private void animatorlayoutoffset(float offset) {
  if (animator != null && animator.isrunning()) {
   return;
  }
  animator = objectanimator.offloat(this, "layoutoffset", layoutoffset, offset);
  animator.setduration(500);
  animator.start();
 }

项目地址在这：

github

总结

以上所述是小编给大家介绍的android 根据手势顶部view自动展示与隐藏效果，希望对大家有所帮助