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      1 /*
      2  * Copyright (C) 2016 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 package android.car.cluster.renderer;
     17 
     18 import android.annotation.Nullable;
     19 import android.car.navigation.CarNavigationInstrumentCluster;
     20 import android.graphics.Bitmap;
     21 import android.os.Bundle;
     22 import android.os.Handler;
     23 import android.os.Looper;
     24 import android.os.Message;
     25 
     26 import java.lang.ref.WeakReference;
     27 import java.util.concurrent.CountDownLatch;
     28 
     29 /**
     30  * A wrapper over {@link NavigationRenderer} that runs all its methods in the context of provided
     31  * looper. It is guaranteed that all calls will be invoked in order they were called.
     32  */
     33 // TODO(deanh): Does this class even need to exist?
     34 /* package */ class ThreadSafeNavigationRenderer extends NavigationRenderer {
     35 
     36     private final Handler mHandler;
     37     private final NavigationRenderer mRenderer;
     38 
     39     private final static int MSG_EVENT = 1;
     40 
     41     /** Creates thread-safe {@link NavigationRenderer}. Returns null if renderer == null */
     42     @Nullable
     43     static NavigationRenderer createFor(Looper looper, NavigationRenderer renderer) {
     44         return renderer == null ? null : new ThreadSafeNavigationRenderer(looper, renderer);
     45     }
     46 
     47     private ThreadSafeNavigationRenderer(Looper looper, NavigationRenderer renderer) {
     48         mRenderer = renderer;
     49         mHandler = new NavigationRendererHandler(looper, renderer);
     50     }
     51 
     52     @Override
     53     public CarNavigationInstrumentCluster getNavigationProperties() {
     54         if (mHandler.getLooper() == Looper.myLooper()) {
     55             return mRenderer.getNavigationProperties();
     56         } else {
     57             return runAndWaitResult(mHandler,
     58                     new RunnableWithResult<CarNavigationInstrumentCluster>() {
     59                         @Override
     60                         protected CarNavigationInstrumentCluster createResult() {
     61                             return mRenderer.getNavigationProperties();
     62                         }
     63                     });
     64         }
     65     }
     66 
     67     @Override
     68     public void onEvent(int eventType, Bundle bundle) {
     69         mHandler.sendMessage(mHandler.obtainMessage(MSG_EVENT, eventType, 0, bundle));
     70     }
     71 
     72     private static class NavigationRendererHandler extends RendererHandler<NavigationRenderer> {
     73 
     74         NavigationRendererHandler(Looper looper, NavigationRenderer renderer) {
     75             super(looper, renderer);
     76         }
     77 
     78         @Override
     79         public void handleMessage(Message msg, NavigationRenderer renderer) {
     80             switch (msg.what) {
     81                 case MSG_EVENT:
     82                     Bundle bundle = (Bundle) msg.obj;
     83                     renderer.onEvent(msg.arg1, bundle);
     84                     break;
     85                 default:
     86                     throw new IllegalArgumentException("Msg: " + msg.what);
     87             }
     88         }
     89     }
     90 
     91     private static <E> E runAndWaitResult(Handler handler, final RunnableWithResult<E> runnable) {
     92         final CountDownLatch latch = new CountDownLatch(1);
     93 
     94         Runnable wrappedRunnable = new Runnable() {
     95             @Override
     96             public void run() {
     97                 runnable.run();
     98                 latch.countDown();
     99             }
    100         };
    101 
    102         handler.post(wrappedRunnable);
    103 
    104         try {
    105             latch.await();
    106         } catch (InterruptedException e) {
    107             throw new RuntimeException(e);
    108         }
    109         return runnable.getResult();
    110     }
    111 
    112     private static abstract class RunnableWithResult<T> implements Runnable {
    113         private volatile T result;
    114 
    115         protected abstract T createResult();
    116 
    117         @Override
    118         public void run() {
    119             result = createResult();
    120         }
    121 
    122         public T getResult() {
    123             return result;
    124         }
    125     }
    126 
    127     private static abstract class RendererHandler<T> extends Handler {
    128 
    129         private final WeakReference<T> mRendererRef;
    130 
    131         RendererHandler(Looper looper, T renderer) {
    132             super(looper);
    133             mRendererRef = new WeakReference<>(renderer);
    134         }
    135 
    136         @Override
    137         public void handleMessage(Message msg) {
    138             T renderer = mRendererRef.get();
    139             if (renderer != null) {
    140                 handleMessage(msg, renderer);
    141             }
    142         }
    143 
    144         public abstract void handleMessage(Message msg, T renderer);
    145     }
    146 }
    147