注册BroadcastReceiver不注销是否会导致内存泄露

深藏阁楼爱情的钟 2022-05-13 11:06 206阅读 0赞

ContextImpl\#registerReceiverInternal(...)

private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
                IntentFilter filter, String broadcastPermission,
                Handler scheduler, Context context) {
            IIntentReceiver rd = null;
            if (receiver != null) {
                if (mPackageInfo != null && context != null) {//一般都会进入这里
                    //...
                    rd = mPackageInfo.getReceiverDispatcher(//mPackageInfo是LoadedApk
                        receiver, context, scheduler,
                        mMainThread.getInstrumentation(), true);//然后进入这里
                } else {
                    //...
                    rd = new LoadedApk.ReceiverDispatcher(
                            receiver, context, scheduler, null, true).getIIntentReceiver();
                }
            }
            try {
                return ActivityManagerNative.getDefault().registerReceiver(
                        mMainThread.getApplicationThread(), mBasePackageName,
                        rd, filter, broadcastPermission, userId);
            } catch (RemoteException e) {
                return null;
            }
        }

LoadedApk\#getReceiverDispatcher(...)

public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
                Context context, Handler handler,
                Instrumentation instrumentation, boolean registered) {
            synchronized (mReceivers) {
                LoadedApk.ReceiverDispatcher rd = null;
                ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher> map = null;
                if (registered) {
                    map = mReceivers.get(context);//每个ContextImpl中都保存了一个Map
                    if (map != null) {
                        rd = map.get(r);//如果这个broadcastReceiver已经注册过，就不加入map中
                    }
                }
                if (rd == null) {//如果这个Receiver没有注册过，则创建一个ReceiverDispatcher实例
                    rd = new ReceiverDispatcher(r, context, handler,
                            instrumentation, registered);
                    if (registered) {
                        if (map == null) {
                            map = new ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher>();
                            mReceivers.put(context, map);
                        }
                        map.put(r, rd);//加入该应用进程堆的Map中
                    }
                } else {
                    rd.validate(context, handler);//查看是否使用不同的Context注册同一个Receiver
                }
                rd.mForgotten = false;
                return rd.getIIntentReceiver();
            }
        }

根据实验和分析源码，其实反复注册同一个BroadcastReceiver实例并不会造成更多的内存泄露。如果一个Activity周期中注册了Receiver，而Activity生命周期结束时，没有注销该Receiver，在onDestroy中，会去LoadedApk中把Activity的注册的BroadcastReceiver及相关的对象销毁，在该Activity中bindService的service也会unbind。所以其实这种泄露比较小。同一个Broadcast Receiver使用不同的Context注册时，会相当于多次注册，和创建多个IIntentReceiver。如果使用同一Context对同一个Receiver对象注册，在应用中不会新增任何对象，只是如果使用的IntentFilter没有注册过，则在AMS中新增一个BroadcastFilter对象。