Analysis of static broadcast transmission process

The last article analyzed dynamic broadcasting （NR>0 Because it's dynamic regist I will put bf Add to mReceiverResolver This AMS In local variables , If it is static, the query cannot find mReceiverResolver In variables bf）, Next, analyze the statically registered broadcast , Static registered broadcast receivers Not for null.

Summary ：1. First get the dynamically registered broadcast and statically registered broadcast , And store these broadcasts in two different lists

2. Determine whether it is an ordinary broadcast sent , If it is , And dynamically registered broadcast , The dynamically registered broadcast will be sent first ,  Follow the subsequent broadcast transmission process , Then determine whether there is a static broadcast , If there is a static broadcast , Then send static broadcast .( From the source code logic, we can know , Transmission of ordinary broadcast , Is dynamic broadcast priority static broadcast transmission ) If you're sending an ordered broadcast , The two lists in step 1 will be merged into receivers In the list , And sort the broadcasts according to priority , The specific sorting rule is , The one with high priority is in the front , For the same priority , Dynamic priority static priority , For the same priority , The broadcast type is the same , If they are all dynamic broadcast types , Those registered first have priority and those registered later , For all static broadcast types , Scan first, because scan later .

3. The broadcast list of the second step , Add to BroadcastQueue Of mParallelBroadcasts perhaps mOrderedBroadcasts in , If the broadcast is sent in the normal way , The broadcast is stored in mParallelBroadcasts In the list , If it is a static broadcast, it is stored in mOrderedBroadcasts In the list , If the transmission mode is orderly broadcast , Then all the broadcasts ( Whether statically registered or dynamically registered ) Are stored in the mOrderedBroadcasts In the list .

• Dynamic broadcasting ： By calling BroadcastQueue Of enqueueOrderedBroadcastLocked Method stores the transmitted broadcast in BroadcastQueue Of mParallelBroadcasts In the list , And then through scheduleBroadcastsLocked Method send broadcast .

there mBroadcastsScheduled Express ActivityManagerService Are other broadcasts currently being processed , If so , Here we will return directly without processing , Ensure all broadcast serial processing . Notice how the broadcast is handled here , It is handled through a message loop , whenever AMS When a broadcast is received , It puts the broadcast into its own message queue and it's done , It doesn't matter if the broadcast is processed later , therefore , Here we can see that the broadcast sending and processing are asynchronous . Member variables here mHandler It's a ActivityManagerService Internally defined Handler Class variables , Through it sendEmptyMessage The function takes a type as BROADCAST_INTENT_MSG Put empty messages into AMS In the message queue . The empty message here means that the message has type information , No other additional information , Because the broadcast information to be processed has been saved in mParcelBroadcasts It's in , When processing this message , from mParcelBroadcasts You can read back the relevant broadcast information , therefore , There is no need to put the broadcast information in the message content .