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);
}
private void prepareAnimation() {
yMap.clear();
positionMap.clear();
beforeVisible.clear();
afterVisible.clear();
adapter.setMayNotify(false);
final int childCount = getChildCount();
final int firstVisiblePosition = getFirstVisiblePosition();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final long id = adapter.getItemId(firstVisiblePosition + i);
yMap.put(id, ViewHelper.getY(child));
positionMap.put(id, firstVisiblePosition + i);
}
for (int i = 0; i < firstVisiblePosition; i++) {
final long id = adapter.getItemId(i);
beforeVisible.add(id);
}
final int count = adapter.getCount();
for (int i = firstVisiblePosition + childCount; i < count; i++) {
final long id = adapter.getItemId(i);
afterVisible.add(id);
}
}
protected int getPositionForId(final long id) {
for (int i = 0; i < adapter.getCount(); i++) {
if (adapter.getItemId(i) == id) {
return i;
}
}
return -1;
}
