StableIdKeyProvider.java
/*
* Copyright 2017 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.recyclerview.selection;
import static androidx.recyclerview.selection.Shared.DEBUG;
import android.util.Log;
import android.util.SparseArray;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.collection.LongSparseArray;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.RecyclerView.OnChildAttachStateChangeListener;
/**
* An {@link ItemKeyProvider} that provides stable ids by way of cached
* {@link RecyclerView.Adapter} stable ids. Items enter the cache as they are laid out by
* RecyclerView, and are removed from the cache as they are recycled.
*
* <p>
* There are trade-offs with this implementation as it necessarily auto-boxes {@code long}
* stable id values into {@code Long} values for use as selection keys. The core Selection API
* uses a parameterized key type to permit other keys (such as Strings or URIs).
*/
public final class StableIdKeyProvider extends ItemKeyProvider<Long> {
private static final String TAG = "StableIdKeyProvider";
private final SparseArray<Long> mPositionToKey = new SparseArray<>();
private final LongSparseArray<Integer> mKeyToPosition = new LongSparseArray<>();
private final RecyclerView mRecyclerView;
/**
* Creates a new key provider that uses cached {@code long} stable ids associated
* with the RecyclerView items.
*
* @param recyclerView the owner RecyclerView
*/
public StableIdKeyProvider(@NonNull RecyclerView recyclerView) {
// Since this provide is based on stable ids based on whats laid out in the window
// we can only satisfy "window" scope key access.
super(SCOPE_CACHED);
mRecyclerView = recyclerView;
mRecyclerView.addOnChildAttachStateChangeListener(
new OnChildAttachStateChangeListener() {
@Override
public void onChildViewAttachedToWindow(View view) {
onAttached(view);
}
@Override
public void onChildViewDetachedFromWindow(View view) {
onDetached(view);
}
}
);
}
@SuppressWarnings("WeakerAccess") /* synthetic access */
void onAttached(@NonNull View view) {
RecyclerView.ViewHolder holder = mRecyclerView.findContainingViewHolder(view);
if (holder == null) {
if (DEBUG) {
Log.w(TAG, "Unable to find ViewHolder for View. Ignoring onAttached event.");
}
return;
}
int position = holder.getAdapterPosition();
long id = holder.getItemId();
if (position != RecyclerView.NO_POSITION && id != RecyclerView.NO_ID) {
mPositionToKey.put(position, id);
mKeyToPosition.put(id, position);
}
}
@SuppressWarnings("WeakerAccess") /* synthetic access */
void onDetached(@NonNull View view) {
RecyclerView.ViewHolder holder = mRecyclerView.findContainingViewHolder(view);
if (holder == null) {
if (DEBUG) {
Log.w(TAG, "Unable to find ViewHolder for View. Ignoring onDetached event.");
}
return;
}
int position = holder.getAdapterPosition();
long id = holder.getItemId();
if (position != RecyclerView.NO_POSITION && id != RecyclerView.NO_ID) {
mPositionToKey.delete(position);
mKeyToPosition.remove(id);
}
}
@Override
public @Nullable Long getKey(int position) {
return mPositionToKey.get(position, null);
}
@Override
public int getPosition(@NonNull Long key) {
return mKeyToPosition.get(key, RecyclerView.NO_POSITION);
}
}