/**
* This method takes layout manager and finds the right center element of it
*
* @param layoutManager
* @return View
*/
private View findCenterView(LinearLayoutManager layoutManager) {
int minDistance = 0;
View view, returnView = null;
boolean notFound = true;
for (int i = layoutManager.findFirstVisibleItemPosition();
i <= layoutManager.findLastVisibleItemPosition() && notFound;
i++) {
view = layoutManager.findViewByPosition(i);
int center = (view.getLeft() + view.getRight()) / 2;
int leastDifference = Math.abs(mCenterPivot - center);
if (leastDifference <= minDistance || i == layoutManager.findFirstVisibleItemPosition()) {
minDistance = leastDifference;
returnView = view;
} else {
notFound = false;
}
}
return returnView;
}
private View findCenterView(LinearLayoutManager lm) {
int minDistance = 0;
View view = null;
View returnView = null;
boolean notFound = true;
for (int i = lm.findFirstVisibleItemPosition();
i <= lm.findLastVisibleItemPosition() && notFound;
i++) {
view = lm.findViewByPosition(i);
int center =
lm.getOrientation() == LinearLayoutManager.HORIZONTAL
? (view.getLeft() + view.getRight()) / 2
: (view.getTop() + view.getBottom()) / 2;
int leastDifference = Math.abs(mCenterPivot - center);
if (leastDifference <= minDistance || i == lm.findFirstVisibleItemPosition()) {
minDistance = leastDifference;
returnView = view;
setCenterView(returnView);
} else {
notFound = false;
}
}
return returnView;
}
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
LinearLayoutManager linearLayoutManager =
(LinearLayoutManager) recyclerView.getLayoutManager();
if (mCenterPivot == 0) {
mCenterPivot = recyclerView.getLeft() + recyclerView.getRight();
}
if (!mAutoSet) {
synchronized (this) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
View view = linearLayoutManager.findViewByPosition(mPosition);
mPosition = INITIAL_POSITION;
if (view == null) {
view = findCenterView(linearLayoutManager);
}
int viewCenter = (view.getLeft() + view.getRight()) / 2;
int viewWidth = view.getRight() - view.getLeft();
int scrollNeeded = viewCenter - mCenterPivot;
if (BuildConfig.DEBUG)
Log.d(
TAG,
"viewCentre = "
+ viewCenter
+ " viewWidth = "
+ viewWidth
+ " scrollNeeded = "
+ scrollNeeded
+ " recyclerViewWidth = "
+ recyclerView.getMeasuredWidth());
recyclerView.smoothScrollBy(scrollNeeded, 0);
mCenterHolderPosition = recyclerView.getChildLayoutPosition(view);
if (BuildConfig.DEBUG)
Log.d(
TAG,
"centerHolderPosition = " + mCenterHolderPosition + " mPosition = " + mPosition);
if (mScrollType == null) {
mScrollType = SwipeType.SWIPE;
}
onCenterItemSnap(
mCenterHolderPosition, recyclerView.getChildViewHolder(view), mScrollType);
mScrollType = null;
mAutoSet = true;
}
}
}
if (newState == RecyclerView.SCROLL_STATE_DRAGGING
|| newState == RecyclerView.SCROLL_STATE_SETTLING) {
mAutoSet = false;
}
}