private void updateOrClearHeader(int firstVisiblePosition) {
final int adapterCount = mAdapter == null ? 0 : mAdapter.getCount();
if (adapterCount == 0 || !mAreHeadersSticky) {
return;
}
final int headerViewCount = mList.getHeaderViewsCount();
int headerPosition = firstVisiblePosition - headerViewCount;
if (mList.getChildCount() > 0) {
View firstItem = mList.getChildAt(0);
if (firstItem.getBottom() < stickyHeaderTop()) {
headerPosition++;
}
}
// 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() >= stickyHeaderTop();
final boolean isHeaderPositionOutsideAdapterRange =
headerPosition > adapterCount - 1 || headerPosition < 0;
if (!doesListHaveChildren || isHeaderPositionOutsideAdapterRange || isFirstViewBelowTop) {
clearHeader();
return;
}
updateHeader(headerPosition);
}
// hides the headers in the list under the sticky header.
// Makes sure the other ones are showing
private void updateHeaderVisibilities() {
int top;
if (mHeader != null) {
top = mHeader.getMeasuredHeight() + (mHeaderOffset != null ? mHeaderOffset : 0);
} else {
top = mClippingToPadding ? mPaddingTop : 0;
}
int childCount = mList.getChildCount();
for (int i = 0; i < childCount; i++) {
View child = mList.getChildAt(i);
if (child instanceof WrapperView) {
WrapperView wrapperViewChild = (WrapperView) child;
if (wrapperViewChild.hasHeader()) {
View childHeader = wrapperViewChild.mHeader;
if (wrapperViewChild.getTop() < top) {
if (childHeader.getVisibility() != View.INVISIBLE) {
childHeader.setVisibility(View.INVISIBLE);
}
} else {
if (childHeader.getVisibility() != View.VISIBLE) {
childHeader.setVisibility(View.VISIBLE);
}
}
}
}
}
}
// hides the headers in the list under the sticky header.
// Makes sure the other ones are showing
private void updateHeaderVisibilities() {
int top = stickyHeaderTop();
int childCount = mList.getChildCount();
for (int i = 0; i < childCount; i++) {
// ensure child is a wrapper view
View child = mList.getChildAt(i);
if (!(child instanceof WrapperView)) {
continue;
}
// ensure wrapper view child has a header
WrapperView wrapperViewChild = (WrapperView) child;
if (!wrapperViewChild.hasHeader()) {
continue;
}
// update header views visibility
View childHeader = wrapperViewChild.mHeader;
if (wrapperViewChild.getTop() < top) {
if (childHeader.getVisibility() != View.INVISIBLE) {
childHeader.setVisibility(View.INVISIBLE);
}
} else {
if (childHeader.getVisibility() != View.VISIBLE) {
childHeader.setVisibility(View.VISIBLE);
}
}
}
}
private void updateHeader(int headerPosition) {
// check if there is a new header should be sticky
if (mHeaderPosition == null || mHeaderPosition != headerPosition) {
mHeaderPosition = headerPosition;
final long headerId = mAdapter.getHeaderId(headerPosition);
if (mHeaderId == null || mHeaderId != headerId) {
mHeaderId = headerId;
final View header = mAdapter.getHeaderView(mHeaderPosition, mHeader, this);
if (mHeader != header) {
if (header == null) {
throw new NullPointerException("header may not be null");
}
swapHeader(header);
}
ensureHeaderHasCorrectLayoutParams(mHeader);
measureHeader(mHeader);
if (mOnStickyHeaderChangedListener != null) {
mOnStickyHeaderChangedListener.onStickyHeaderChanged(
this, mHeader, headerPosition, mHeaderId);
}
// Reset mHeaderOffset to null ensuring
// that it will be set on the header and
// not skipped for performance reasons.
mHeaderOffset = null;
}
}
int headerOffset = 0;
// Calculate new header offset
// Skip looking at the first view. it never matters because it always
// results in a headerOffset = 0
int headerBottom = mHeader.getMeasuredHeight() + stickyHeaderTop();
for (int i = 0; i < mList.getChildCount(); i++) {
final View child = mList.getChildAt(i);
final boolean doesChildHaveHeader =
child instanceof WrapperView && ((WrapperView) child).hasHeader();
final boolean isChildFooter = mList.containsFooterView(child);
if (child.getTop() >= stickyHeaderTop() && (doesChildHaveHeader || isChildFooter)) {
headerOffset = Math.min(child.getTop() - headerBottom, 0);
break;
}
}
setHeaderOffet(headerOffset);
if (!mIsDrawingListUnderStickyHeader) {
mList.setTopClippingLength(mHeader.getMeasuredHeight() + mHeaderOffset);
}
updateHeaderVisibilities();
}
public View getListChildAt(int index) {
return mList.getChildAt(index);
}