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Prevent mScrollY jumping on GridLayoutManager with 2+ columns. #78

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Prevent mScrollY jumping on GridLayoutManager with 2+ columns. #78

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15 changes: 12 additions & 3 deletions ...c/main/java/com/github/ksoichiro/android/observablescrollview/ObservableRecyclerView.java
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Original file line number Diff line number Diff line change
Expand Up @@ -96,15 +96,24 @@ protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if (mCallbacks != null) {
if (getChildCount() > 0) {
int firstVisiblePosition = getChildPosition(getChildAt(0));
int lastVisiblePosition = getChildPosition(getChildAt(getChildCount() - 1));
int firstVisiblePosition;
int lastVisiblePosition;

if (getLayoutManager() instanceof LinearLayoutManager) {
LinearLayoutManager manager = (LinearLayoutManager) getLayoutManager();
firstVisiblePosition = manager.findFirstVisibleItemPosition();
lastVisiblePosition = manager.findLastVisibleItemPosition();
} else {
throw new IllegalArgumentException("need to be an LinearLayoutManager child");
}

for (int i = firstVisiblePosition, j = 0; i <= lastVisiblePosition; i++, j++) {
if (mChildrenHeights.indexOfKey(i) < 0 || getChildAt(j).getHeight() != mChildrenHeights.get(i)) {
mChildrenHeights.put(i, getChildAt(j).getHeight());
}
}

View firstVisibleChild = getChildAt(0);
View firstVisibleChild = getChildAt(firstVisiblePosition);
if (firstVisibleChild != null) {
if (mPrevFirstVisiblePosition < firstVisiblePosition) {
// scroll down
Expand Down