| Adam Powell | c9fda28 | 2019-12-05 09:49:48 -0800 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2019 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package androidx.lifecycle; |
| 18 | |
| 19 | import android.view.View; |
| 20 | import android.view.ViewParent; |
| 21 | |
| 22 | import androidx.annotation.NonNull; |
| 23 | import androidx.annotation.Nullable; |
| 24 | |
| 25 | /** |
| 26 | * Accessors for finding a view tree-local {@link LifecycleOwner} that reports the lifecycle for |
| 27 | * the given view. |
| 28 | */ |
| 29 | public class ViewTreeLifecycleOwner { |
| 30 | private ViewTreeLifecycleOwner() { |
| 31 | // No instances |
| 32 | } |
| 33 | |
| 34 | /** |
| 35 | * Set the {@link LifecycleOwner} responsible for managing the given {@link View}. |
| 36 | * Calls to {@link #get(View)} from this view or descendants will return {@code lifecycleOwner}. |
| 37 | * |
| 38 | * <p>This should only be called by constructs such as activities or fragments that manage |
| 39 | * a view tree and reflect their own lifecycle through a {@link LifecycleOwner}. Callers |
| 40 | * should only set a {@link LifecycleOwner} that will be <em>stable.</em> The associated |
| 41 | * lifecycle should report that it is destroyed if the view tree is removed and is not |
| 42 | * guaranteed to later become reattached to a window.</p> |
| 43 | * |
| 44 | * @param view Root view managed by lifecycleOwner |
| 45 | * @param lifecycleOwner LifecycleOwner representing the manager of the given view |
| 46 | */ |
| 47 | public static void set(@NonNull View view, @Nullable LifecycleOwner lifecycleOwner) { |
| 48 | view.setTag(R.id.view_tree_lifecycle_owner, lifecycleOwner); |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * Retrieve the {@link LifecycleOwner} responsible for managing the given {@link View}. |
| 53 | * This may be used to scope work or heavyweight resources associated with the view |
| 54 | * that may span cycles of the view becoming detached and reattached from a window. |
| 55 | * |
| 56 | * @param view View to fetch a {@link LifecycleOwner} for |
| 57 | * @return The {@link LifecycleOwner} responsible for managing this view and/or some subset |
| 58 | * of its ancestors |
| 59 | */ |
| 60 | @Nullable |
| 61 | public static LifecycleOwner get(@NonNull View view) { |
| 62 | LifecycleOwner found = (LifecycleOwner) view.getTag(R.id.view_tree_lifecycle_owner); |
| 63 | if (found != null) return found; |
| 64 | ViewParent parent = view.getParent(); |
| 65 | while (found == null && parent instanceof View) { |
| 66 | final View parentView = (View) parent; |
| 67 | found = (LifecycleOwner) parentView.getTag(R.id.view_tree_lifecycle_owner); |
| 68 | parent = parentView.getParent(); |
| 69 | } |
| 70 | return found; |
| 71 | } |
| 72 | } |
