| /* |
| * 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 android.util.SparseArray; |
| import android.view.View; |
| |
| import androidx.annotation.NonNull; |
| import androidx.annotation.Nullable; |
| import androidx.recyclerview.widget.RecyclerView; |
| import androidx.recyclerview.widget.RecyclerView.OnChildAttachStateChangeListener; |
| |
| import java.util.HashMap; |
| import java.util.Map; |
| |
| /** |
| * 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 final SparseArray<Long> mPositionToKey = new SparseArray<>(); |
| private final Map<Long, Integer> mKeyToPosition = new HashMap<Long, Integer>(); |
| 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); |
| } |
| } |
| ); |
| |
| } |
| |
| private void onAttached(@NonNull View view) { |
| RecyclerView.ViewHolder holder = mRecyclerView.findContainingViewHolder(view); |
| 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); |
| } |
| } |
| |
| private void onDetached(@NonNull View view) { |
| RecyclerView.ViewHolder holder = mRecyclerView.findContainingViewHolder(view); |
| 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) { |
| if (mKeyToPosition.containsKey(key)) { |
| return mKeyToPosition.get(key); |
| } |
| return RecyclerView.NO_POSITION; |
| } |
| } |