2020-06-23-Android下registerReceiver为什么会内存泄漏

开发过程中，如果需要动态注册广告，我们需要调用registerReceiver方法实现动态注册广告，如果没有调用unregisterReceiver会导致内存泄漏，这是为什么呢？

以Context类来说，registerReceiver和unregisterReceiver都是2个abstract方法

    @Nullable
    public abstract Intent registerReceiver(@Nullable BroadcastReceiver receiver,
                                            IntentFilter filter);

    /**
     * Unregister a previously registered BroadcastReceiver.（注销先前注册过的BroadcastReceiver）  All
     * filters that have been registered for this BroadcastReceiver will be
     * removed.
     *
     * @param receiver The BroadcastReceiver to unregister.
     *
     * @see #registerReceiver
     */
    public abstract void unregisterReceiver(BroadcastReceiver receiver);

Context的三兄弟关系，我就在这里解说了，打开
http://androidxref.com/7.1.2_r36/xref/frameworks/base/core/java/android/app/ContextImpl.java
查看ContextImpl.java的实现

  @Override
    public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
        return registerReceiver(receiver, filter, null, null);
    }

在跟踪代码可以看到

ActivityManagerNative.getDefault().registerReceiver(mMainThread.getApplicationThread(), mBasePackageName,rd, filter, broadcastPermission, userId);

    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) {
                if (scheduler == null) {
                    scheduler = mMainThread.getHandler();
                }
                rd = mPackageInfo.getReceiverDispatcher(
                    receiver, context, scheduler,
                    mMainThread.getInstrumentation(), true);
            } else {
                if (scheduler == null) {
                    scheduler = mMainThread.getHandler();
                }
                rd = new LoadedApk.ReceiverDispatcher(
                        receiver, context, scheduler, null, true).getIIntentReceiver();
            }
        }
        try {
            final Intent intent = ActivityManagerNative.getDefault().registerReceiver(
                    mMainThread.getApplicationThread(), mBasePackageName,
                    rd, filter, broadcastPermission, userId);
            if (intent != null) {
                intent.setExtrasClassLoader(getClassLoader());
                intent.prepareToEnterProcess();
            }
            return intent;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

    @Override
    public void unregisterReceiver(BroadcastReceiver receiver) {
        if (mPackageInfo != null) {
            IIntentReceiver rd = mPackageInfo.forgetReceiverDispatcher(
                    getOuterContext(), receiver);
            try {
                ActivityManagerNative.getDefault().unregisterReceiver(rd);
            } catch (RemoteException e) {
                throw e.rethrowFromSystemServer();
            }
        } else {
            throw new RuntimeException("Not supported in system context");
        }
    }

ActivityManagerNative实现动态注册广告，利用binder（AIDL）的transact方法REGISTER_RECEIVER_TRANSACTION和UNREGISTER_RECEIVER_TRANSACTION实现注册和反注册

mRemote.transact(REGISTER_RECEIVER_TRANSACTION, data, reply, 0);

基于观察者模式的原理，如果不取消的话，在ActivityManagerNative的成员变量

 private IBinder mRemote;

就会一直持有对象

另外一个问题？

在ActivityManagerNative里面有一个内部类

image.png

这算不算内部类持有的问题？？

image.png