BroadcastReceiver学习笔记
BroadcastReceiver 注册过程
BroadcastReceiver 注册的过程大致如下图所示：
+----------------+ +-------------+ +-------------------------+ +------------------------+ | ContextWrapper | | ContextImpl | | LoadedApk(mPackageInfo) | | ActivityManagerService | +-----+----------+ +------+------+ +------------+------------+ +---------------+--------+ || | | || | | registerReceiver|| | | || | | +--------------->| | | | registerReceiver| | | || | | +------------------------> | | || getReceiverDispatcher | | || | | |+---------------------------> | || | | || [IIntentReceiver] | | || | | |<---------------------------+ registerReceiver | || | | |+-------------------------------------------------------------> || | | || | | vv v v 调用ContextWrapper的registerReceiver方法，然后传入receiver实例和filter实例。
调用ContextImpl的registerReceiverInternal方法， 由LoadedApk类将context、receiver、scheduler（receiver所在进程的handler）等包装成ReceiverDispatcher类。并将其内部类IIntentReceiver返回，传给ActivityManagerService进行注册。
LoadeApk中与BroadcastReceiver注册相关的类结构图如下所示：
+-------------------------------------------------------------+ | LoadedApk | | | | +-------------------+ | | | mReceivers | +-----------------------+ | | +-------------------+ | receiver1->dispatcher | | | | context(Activity)+--------> | | | | | | receiver2->dispatcher | | | | context | | | | | | | | receiver3->dispatcher | | | | context | | | | | | | | ... | | | | ... | +-----------------------+ | | +-------------------+ | | | | | +-------------------------------------------------------------+ LoadedApk中保存着context与其注册的各个receiver的对应关系，同时也保存着每个receiver与其dispatcher的对应关系。
dispatcher中的IIntentReceiver是与ActivityManagerService沟通的桥梁。其内部结构如下图所示：
+--------------------------------------------------+| ReceiverDispatcher || +-------------------------------------------+ || | InnerReceiver extends IIntentReceiver.Stub| || +-------------------------------------------+ || || BroadcastReceiver mReceiver; || Context mContext; || Handler mActivityThread; || |+--------------------------------------------------+ActivityManagerService在其registerReceiver方法中，将传入的IIntentReceiver和filter以及caller保存成如下所示的结构：
+---------------------------------------------------------------------------+ | | | ActivityManagerService | | +---------------------+ | | | ReceiverList | | | +-------------+ +---------------------+ | | +-->InnerReceiver+--> BroadcastFilter1 | | | +---------------------+ | +-------------+ | | | | | mRegisteredReceivers+--+ | BroadcastFilter2 | | | +---------------------+ | | | | | | +-------------+ | ... | | | +-->InnerReceiver| +---------------------+ | | | +-------------+| | | | | | | | +--> ... | | | | | | +------------------+| | +-------------------+ | BroadcastFilter1 || | | mReceiverResolver +---> || | +-------------------+ | BroadcastFilter2 || | | || | | ... || | +------------------+| | | +---------------------------------------------------------------------------+ 保存成这种结构的原因是为后面发送Broadcast提供高效的实现。