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      1 /*
      2  * Copyright (C) 2017 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.app.Service;
     20 import android.content.Intent;
     21 import android.os.Handler;
     22 
     23 import androidx.annotation.NonNull;
     24 
     25 /**
     26  * Helper class to dispatch lifecycle events for a service. Use it only if it is impossible
     27  * to use {@link LifecycleService}.
     28  */
     29 @SuppressWarnings("WeakerAccess")
     30 public class ServiceLifecycleDispatcher {
     31     private final LifecycleRegistry mRegistry;
     32     private final Handler mHandler;
     33     private DispatchRunnable mLastDispatchRunnable;
     34 
     35     /**
     36      * @param provider {@link LifecycleOwner} for a service, usually it is a service itself
     37      */
     38     public ServiceLifecycleDispatcher(@NonNull LifecycleOwner provider) {
     39         mRegistry = new LifecycleRegistry(provider);
     40         mHandler = new Handler();
     41     }
     42 
     43     private void postDispatchRunnable(Lifecycle.Event event) {
     44         if (mLastDispatchRunnable != null) {
     45             mLastDispatchRunnable.run();
     46         }
     47         mLastDispatchRunnable = new DispatchRunnable(mRegistry, event);
     48         mHandler.postAtFrontOfQueue(mLastDispatchRunnable);
     49     }
     50 
     51     /**
     52      * Must be a first call in {@link Service#onCreate()} method, even before super.onCreate call.
     53      */
     54     public void onServicePreSuperOnCreate() {
     55         postDispatchRunnable(Lifecycle.Event.ON_CREATE);
     56     }
     57 
     58     /**
     59      * Must be a first call in {@link Service#onBind(Intent)} method, even before super.onBind
     60      * call.
     61      */
     62     public void onServicePreSuperOnBind() {
     63         postDispatchRunnable(Lifecycle.Event.ON_START);
     64     }
     65 
     66     /**
     67      * Must be a first call in {@link Service#onStart(Intent, int)} or
     68      * {@link Service#onStartCommand(Intent, int, int)} methods, even before
     69      * a corresponding super call.
     70      */
     71     public void onServicePreSuperOnStart() {
     72         postDispatchRunnable(Lifecycle.Event.ON_START);
     73     }
     74 
     75     /**
     76      * Must be a first call in {@link Service#onDestroy()} method, even before super.OnDestroy
     77      * call.
     78      */
     79     public void onServicePreSuperOnDestroy() {
     80         postDispatchRunnable(Lifecycle.Event.ON_STOP);
     81         postDispatchRunnable(Lifecycle.Event.ON_DESTROY);
     82     }
     83 
     84     /**
     85      * @return {@link Lifecycle} for the given {@link LifecycleOwner}
     86      */
     87     public Lifecycle getLifecycle() {
     88         return mRegistry;
     89     }
     90 
     91     static class DispatchRunnable implements Runnable {
     92         private final LifecycleRegistry mRegistry;
     93         final Lifecycle.Event mEvent;
     94         private boolean mWasExecuted = false;
     95 
     96         DispatchRunnable(@NonNull LifecycleRegistry registry, Lifecycle.Event event) {
     97             mRegistry = registry;
     98             mEvent = event;
     99         }
    100 
    101         @Override
    102         public void run() {
    103             if (!mWasExecuted) {
    104                 mRegistry.handleLifecycleEvent(mEvent);
    105                 mWasExecuted = true;
    106             }
    107         }
    108     }
    109 }
    110