android.widget.AdapterView#getChildAt ( )源码实例Demo

private boolean isAdapterViewTop(AdapterView adapterView) {
    if (adapterView != null) {
        int firstVisiblePosition = adapterView.getFirstVisiblePosition();
        View childAt = adapterView.getChildAt(0);
        if (childAt == null || (firstVisiblePosition == 0 && childAt.getTop() == 0)) {
            return true;
        }
    }
    return false;
}
 

private static boolean isAdapterViewTop(AdapterView adapterView) {
    if (adapterView != null) {
        int firstVisiblePosition = adapterView.getFirstVisiblePosition();
        View childAt = adapterView.getChildAt(0);
        return childAt == null || (firstVisiblePosition == 0 && childAt.getTop() == 0);
    }
    return false;
}
 

private static boolean isAdapterViewTop(AdapterView adapterView) {
    if (adapterView != null) {
        int firstVisiblePosition = adapterView.getFirstVisiblePosition();
        View childAt = adapterView.getChildAt(0);
        if (childAt == null || (firstVisiblePosition == 0 && childAt != null && childAt.getTop() == 0)) {
            return true;
        }
    }
    return false;
}
 

private boolean canListScroll(int direction) {
    AdapterView<?> absListView = (AdapterView<?>) mTargetView;
    final int itemCount = absListView.getCount();
    final int childCount = absListView.getChildCount();
    final int firstPosition = absListView.getFirstVisiblePosition();
    final int lastPosition = firstPosition + childCount;

    if (itemCount == 0) {
        return false;
    }
    if (direction > 0) {
        // Are we already showing the entire last item?
        if (lastPosition >= itemCount) {
            final View lastView = absListView.getChildAt(childCount - 1);
            if (lastView != null
                    && lastView.getBottom() >= mTargetView.getHeight()) {
                return false;
            }
        }
    } else if (direction < 0) {
        // Are we already showing the entire first item?
        if (firstPosition <= 0) {
            final View firstView = absListView.getChildAt(0);
            if (firstView != null && firstView.getTop() >= 0) {
                return false;
            }
        }
    }
    return true;
}
 

private static boolean isAdapterViewTop(AdapterView adapterView){
    if(adapterView != null){
        int firstVisiblePosition = adapterView.getFirstVisiblePosition();
        View childAt = adapterView.getChildAt(0);
        if(childAt == null || (firstVisiblePosition == 0 && childAt.getTop() == 0)){
            return true;
        }
    }
    return false;
}
 

private boolean isElementFullyRendered(
    AdapterView<? extends Adapter> adapterView, int childAt) {
  View element = adapterView.getChildAt(childAt);
  // Occassionally we'll have to fight with smooth scrolling logic on our definition of when
  // there is extra scrolling to be done. In particular if the element is the first or last
  // element of the list, the smooth scroller may decide that no work needs to be done to scroll
  // to the element if a certain percentage of it is on screen. Ugh. Sigh. Yuck.

  return isDisplayingAtLeast(FULLY_RENDERED_PERCENTAGE_CUTOFF).matches(element);
}
 

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    selectItem(position);
    if(!isActivity(position)){
     	for(int i=0;i<parent.getCount();i++){
      View v=parent.getChildAt(i);
      if (position == i) {
          v.setBackgroundColor(Color.GRAY);
      } else {
          v.setBackgroundColor(Color.TRANSPARENT);
      }
  }
    }
    }