GridLayoutManagerUtils.java
/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.car.util;
import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;
import android.view.View;
import androidx.annotation.RestrictTo;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
/**
* Utility class that helps navigating in GridLayoutManager.
*
* <p>Assumes parameter {@code RecyclerView} uses {@link GridLayoutManager}.
*
* <p>Assumes the orientation of {@code GridLayoutManager} is vertical.
*
* @hide
*/
@RestrictTo(LIBRARY_GROUP_PREFIX)
public class GridLayoutManagerUtils {
private GridLayoutManagerUtils() {}
/**
* Returns the number of items in the first row of a RecyclerView that has a
* {@link GridLayoutManager} as its {@code LayoutManager}.
*
* @param recyclerView RecyclerView that uses GridLayoutManager as LayoutManager.
* @return number of items in the first row in {@code RecyclerView}.
*/
public static int getFirstRowItemCount(RecyclerView recyclerView) {
GridLayoutManager manager = (GridLayoutManager) recyclerView.getLayoutManager();
int itemCount = recyclerView.getAdapter().getItemCount();
int spanCount = manager.getSpanCount();
int spanSum = 0;
int numOfItems = 0;
while (numOfItems < itemCount && spanSum < spanCount) {
spanSum += manager.getSpanSizeLookup().getSpanSize(numOfItems);
numOfItems++;
}
return numOfItems;
}
/**
* Returns the span index of an item.
*/
public static int getSpanIndex(View item) {
GridLayoutManager.LayoutParams layoutParams =
((GridLayoutManager.LayoutParams) item.getLayoutParams());
return layoutParams.getSpanIndex();
}
/**
* Returns whether or not the given view is on the last row of a {@code RecyclerView} with a
* {@link GridLayoutManager}.
*
* @param view The view to inspect.
* @param parent {@link RecyclerView} that contains the given view.
* @return {@code true} if the given view is on the last row of the {@code RecyclerView}.
*/
public static boolean isOnLastRow(View view, RecyclerView parent) {
return getLastItemPositionOnSameRow(view, parent) == parent.getAdapter().getItemCount() - 1;
}
/**
* Returns the position of the last item that is on the same row as input {@code view}.
*
* @param view The view to inspect.
* @param parent {@link RecyclerView} that contains the given view.
*/
public static int getLastItemPositionOnSameRow(View view, RecyclerView parent) {
GridLayoutManager layoutManager = ((GridLayoutManager) parent.getLayoutManager());
GridLayoutManager.SpanSizeLookup spanSizeLookup = layoutManager.getSpanSizeLookup();
int spanCount = layoutManager.getSpanCount();
int lastItemPosition = parent.getAdapter().getItemCount() - 1;
int currentChildPosition = parent.getChildAdapterPosition(view);
int spanSum = getSpanIndex(view) + spanSizeLookup.getSpanSize(currentChildPosition);
// Iterate to the end of the row starting from the current child position.
while (currentChildPosition <= lastItemPosition && spanSum <= spanCount) {
spanSum += spanSizeLookup.getSpanSize(currentChildPosition + 1);
if (spanSum > spanCount) {
return currentChildPosition;
}
currentChildPosition++;
}
return lastItemPosition;
}
}