指标，当我们到达Horizo​​ntalScrollView中的最后一个项目时消失

Question

我有一个Horizo​​ntalScrollView的子类，我在其中添加多个图像。 我必须在屏幕的左右两侧显示某种指示符，以显示左侧和右侧是否有剩余物品。当我们达到相关目标时，各自的指标也应该消失。

有人可以告诉我可用的选项吗？

 protected void onScrollChanged(int l, int t, int oldl, int oldt) { 

      View view = (View) takeparent().getChildAt(takeparent().getChildCount()-1); //this is the last view 
      int diff = (view.getRight()-(getRight()+getScrollX()));// Calculate the scrolldiff 
      if(diff == 0){ // if diff is zero, then the rightmost end has been reached 
       right.setVisibility(View.GONE); //setting the right button invisible 
      } 


      View viewleft = (View) takeparent().getChildAt(0); taking the first View 
      int diffleft2 = (viewleft.getLeft()-(getLeft()+getScrollX()));// Calculate the scrolldiff 

      if(diffleft2 == 0){ // if diff is zero, then the bottom has been reached 
       left.setVisibility(View.GONE); 
       } 



      super.onScrollChanged(l, t, oldl, oldt); 
    } 

Answer 1

这是回答你现在修改的问题：

@Override 
public boolean canScrollHorizontally(int direction) 
{ 
    final int offset = computeHorizontalScrollOffset(); 
    final int range = computeHorizontalScrollRange() - computeHorizontalScrollExtent(); 
    if(range == 0){ 
     return false; 
    } 
    return (direction < 0) ? (offset > 0) : (offset < range - 1); 
} 

protected void onScrollChanged(int l, int t, int oldl, int oldt) 
{ 
    left .setVisibility(canScrollHorizontally(-1) ? View.VISIBLE : View.GONE); 
    right.setVisibility(canScrollHorizontally(1) ? View.VISIBLE : View.GONE); 
} 

我会建议可绘制在使用视图。

因此，我扩展了HorizontalScrollView并重写了draw()方法来绘制它自己的Drawable的canvas的指标。其余的只是使用setBounds来管理它们的位置，现在处于按下状态。

代码：https://gist.github.com/slightfoot/4c017f776663bf6dd5d8#file-indicatedhorizontalscrollview-java