Broadcast Receivers in Android

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Broadcast Receivers simply respond to broadcast messages from other applications or from the system itself. These messages are sometime called events or intents. For example, applications can also initiate broadcasts to let other applications know that some data has been downloaded to the device and is available for them to use, so this is broadcast receiver who will intercept this communication and will initiate appropriate action.

There are following two important steps to make BroadcastReceiver works for the system broadcasted intents −

  • Creating the Broadcast Receiver
  •  Registering Broadcast Receiver

There is one additional steps in case you are going to implement your custom intents then you will have to create and broadcast those intents.

Creating the Broadcast Receiver

A broadcast receiver is implemented as a subclass of BroadcastReceiverclass and overriding the onReceive() method where each message is received as a Intent object parameter.

 

Registering Broadcast Receiver

An application listens for specific broadcast intents by registering a broadcast receiver in AndroidManifest.xml file. Consider we are going to registerMyReceiver for system generated event ACTION_BOOT_COMPLETED which is fired by the system once the Android system has completed the boot process.

br

BROADCAST-RECEIVER

Now whenever your Android device gets booted, it will be intercepted by BroadcastReceiver MyReceiver and implemented logic inside onReceive() will be executed.

There are several system generated events defined as final static fields in theIntent class. The following table lists a few important system events.

Event Constant Description

android.intent.action.BATTERY_CHANGED

Sticky broadcast containing the charging state, level, and other information about the battery.

android.intent.action.BATTERY_LOW

Indicates low battery condition on the device.

android.intent.action.BATTERY_OKAY

Indicates the battery is now okay after being low.

android.intent.action.BOOT_COMPLETED

This is broadcast once, after the system has finished booting.

android.intent.action.BUG_REPORT

Show activity for reporting a bug.

android.intent.action.CALL

Perform a call to someone specified by the data.

android.intent.action.CALL_BUTTON

The user pressed the “call” button to go to the dialer or other appropriate UI for placing a call.

android.intent.action.DATE_CHANGED

The date has changed.

android.intent.action.REBOOT

Have the device reboot.

Broadcasting Custom Intents

If you want your application itself should generate and send custom intents then you will have to create and send those intents by using thesendBroadcast() method inside your activity class. If you use thesendStickyBroadcast(Intent) method, the Intent is sticky, meaning the Intentyou are sending stays around after the broadcast is complete.

 

This intent com.androindian.CUSTOM_INTENT can also be registered in similar way as we have regsitered system generated intent.

 

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