Learn about Android Broadcasts

Below is a summary of core knowledge points for the Android broadcast system:

Real-world analogy: Similar to loudspeakers, radios and televisions, meaning “sent from one location and received by multiple locations”.
Android mechanism: Provides a flexible broadcast messaging system. Each app may register for broadcasts it is interested in to receive only specific content.
Broadcast sources: May come from the system (e.g. device boot, battery level changes) or from other applications.
Sending and receiving: Broadcasts are normally sent via Intent; broadcast reception relies on BroadcastReceiver. Android offers a complete API set to freely send and receive broadcasts.

Android broadcasts are mainly divided into Normal Broadcasts and Ordered Broadcasts. Their core differences are listed below:

Comparison Item	Normal Broadcast	Ordered Broadcast
Execution Mode	Fully asynchronous	Synchronous sequential execution
Reception Timing	All receivers receive simultaneously once dispatched	Only one receiver receives at a time; the next runs only after processing completes
Order of Delivery	No defined order	Ordered delivery; receivers with higher priority get events first
Abort Mechanism	Cannot be aborted; all receivers will receive the broadcast	Earlier receivers may abort the broadcast, blocking subsequent receivers
Performance	High efficiency	Relatively slower (depends on delivery chain)

Normal Broadcast
Broadcast sent → Distributed concurrently to BroadcastReceiver 1, BroadcastReceiver 2, BroadcastReceiver 3 (radial delivery, no interception).
Ordered Broadcast
Broadcast sent → BroadcastReceiver 1 (may abort) → BroadcastReceiver 2 (may abort) → BroadcastReceiver 3 (linear delivery).