Intent flag

1:FLAG_RECEIVER_REPLACE_PENDING

After setting this flag, the new broadcast will replace the unexecuted broadcast that matches this broadcast.

2：FLAG_RECEIVER_REGISTERED_ONLY

Only registered broadcasts in the code are executed

3：FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT

Only the broadcast registered in the code is executed. If FLAG_RECEIVER_REGISTERED_ONLY is set, this flag is unnecessary.

In order to make the system service more convenient to avoid some complicated detection after the startup is completed. Currently hidden API