56.2 An Overview of Broadcast Receivers
An application listens for specific broadcast intents by registering a broadcast receiver. Broadcast receivers are implemented by extending the Android BroadcastReceiver class and overriding the onReceive() method. The broadcast receiver may then be registered, either within code (for example within an activity), or within a manifest file. Part of the registration implementation involves the creation of intent filters to indicate the specific broadcast intents the receiver is required to listen for. This is achieved by referencing the action string of the broadcast intent. When a matching broadcast is detected, the onReceive() method of the broadcast receiver is called, at which point the method has 5 seconds within which to perform any necessary tasks before returning. It is important to note that a broadcast receiver does not need to be running all the time. In the event that a matching intent is detected, the Android runtime system will automatically...