/**
* Locate the visible view which has the earliest adapter position. Will skip headers unless they
* are the only one visible.
*
* @param sectionFirstPosition Position of first position of section..
* @param skipHeader Do not include the section header if it has one.
* @return View.
*/
public View getFirstVisibleView(int sectionFirstPosition, boolean skipHeader) {
int lookAt = 0;
int childCount = mLayoutManager.getChildCount();
View candidate = null;
while (true) {
if (lookAt >= childCount) {
return candidate;
}
final View view = mLayoutManager.getChildAt(lookAt);
LayoutManager.LayoutParams lp = (LayoutManager.LayoutParams) view.getLayoutParams();
if (sectionFirstPosition == lp.getTestedFirstPosition()) {
if (!lp.isHeader || !skipHeader) {
return view;
} else {
candidate = view;
}
} else {
// Skipped past section.
return candidate;
}
lookAt += 1;
}
}
/**
* Find the lowest displayed edge of the section. If there is no member found then return the
* default edge instead.
*
* @param sectionFirstPosition Section id, position of first item in the section.
* @param lastIndex Index to start looking from. Usually the index of the last attached view in
* this section.
* @param defaultEdge Default value.
* @return Lowest (attached) edge of the section.
*/
public int getLowestEdge(int sectionFirstPosition, int lastIndex, int defaultEdge) {
// Look from end to find children that are the lowest.
for (int i = lastIndex; i >= 0; i--) {
View child = mLayoutManager.getChildAt(i);
LayoutManager.LayoutParams params = (LayoutManager.LayoutParams) child.getLayoutParams();
if (params.getTestedFirstPosition() != sectionFirstPosition) {
break;
}
if (params.isHeader) {
continue;
}
// A more interesting layout would have to do something more here.
return mLayoutManager.getDecoratedBottom(child);
}
return defaultEdge;
}
/**
* Find the highest displayed edge of the section. If there is no member found then return the
* default edge instead.
*
* @param sectionFirstPosition Section id, position of first item in the section.
* @param firstIndex Child index to start looking from.
* @param defaultEdge Default value.
* @return Top (attached) edge of the section.
*/
public int getHighestEdge(int sectionFirstPosition, int firstIndex, int defaultEdge) {
// Look from start to find children that are the highest.
for (int i = firstIndex; i < mLayoutManager.getChildCount(); i++) {
View child = mLayoutManager.getChildAt(i);
LayoutManager.LayoutParams params = (LayoutManager.LayoutParams) child.getLayoutParams();
if (params.getTestedFirstPosition() != sectionFirstPosition) {
break;
}
if (params.isHeader) {
continue;
}
// A more interesting layout would have to do something more here.
return mLayoutManager.getDecoratedTop(child);
}
return defaultEdge;
}
/**
* Locate the last view in this section that is completely visible. Will skip headers unless they
* are the only one visible.
*
* @param sectionFirstPosition First position of section being queried.
* @return Last completely visible item or null.
*/
public View getLastCompletelyVisibleView(int sectionFirstPosition) {
final int topEdge = mLayoutManager.getClipToPadding() ? mLayoutManager.getPaddingTop() : 0;
final int bottomEdge =
mLayoutManager.getClipToPadding()
? mLayoutManager.getHeight() - mLayoutManager.getPaddingBottom()
: mLayoutManager.getHeight();
int lookAt = mLayoutManager.getChildCount() - 1;
View candidate = null;
while (true) {
if (lookAt < 0) {
return candidate;
}
final View view = mLayoutManager.getChildAt(lookAt);
final boolean topInside = mLayoutManager.getDecoratedTop(view) >= topEdge;
final boolean bottomInside = mLayoutManager.getDecoratedBottom(view) <= bottomEdge;
LayoutManager.LayoutParams lp = (LayoutManager.LayoutParams) view.getLayoutParams();
if (sectionFirstPosition == lp.getTestedFirstPosition()) {
if (topInside && bottomInside) {
if (!lp.isHeader) {
return view;
} else {
candidate = view;
}
}
} else if (candidate == null) {
sectionFirstPosition = lp.getTestedFirstPosition();
continue;
} else {
return candidate;
}
lookAt -= 1;
}
}
/**
* Locate the visible view which has the latest adapter position.
*
* @param sectionFirstPosition Section id.
* @return View.
*/
public View getLastVisibleView(int sectionFirstPosition) {
int lookAt = mLayoutManager.getChildCount() - 1;
View candidate = null;
while (true) {
if (lookAt < 0) {
return candidate;
}
View view = mLayoutManager.getChildAt(lookAt);
LayoutManager.LayoutParams lp = (LayoutManager.LayoutParams) view.getLayoutParams();
if (sectionFirstPosition == lp.getTestedFirstPosition()) {
if (!lp.isHeader) {
return view;
} else {
candidate = view;
}
} else {
// Skipped past section.
return candidate;
}
lookAt -= 1;
}
}
