private void updateOrClearHeader(int firstVisiblePosition) {
final int adapterCount = mAdapter == null ? 0 : mAdapter.getCount();
if (adapterCount == 0 || !mAreHeadersSticky) {
return;
}
final int headerViewCount = mList.getHeaderViewsCount();
final int realFirstVisibleItem = firstVisiblePosition - headerViewCount;
// It is not a mistake to call getFirstVisiblePosition() here.
// Most of the time getFixedFirstVisibleItem() should be called
// but that does not work great together with getChildAt()
final boolean doesListHaveChildren = mList.getChildCount() != 0;
final boolean isFirstViewBelowTop =
doesListHaveChildren
&& mList.getFirstVisiblePosition() == 0
&& mList.getChildAt(0).getTop() > 0;
final boolean isFirstVisibleItemOutsideAdapterRange =
realFirstVisibleItem > adapterCount - 1 || realFirstVisibleItem < 0;
if (!doesListHaveChildren || isFirstVisibleItemOutsideAdapterRange || isFirstViewBelowTop) {
clearHeader();
return;
}
updateHeader(realFirstVisibleItem);
}
public int getHeaderViewsCount() {
return mList.getHeaderViewsCount();
}