Công Nghệ Android

Broadcast receiver service android example

Broadcast in android is the system-wide events that can occur when the device starts, when a message is received on the device or when incoming calls are received, or when a device goes to airplane mode, etc. Broadcast Receivers are used to respond to these system-wide events. Broadcast Receivers allow us to register for the system and application events, and when that event happens, then the register receivers get notified. There are mainly two types of Broadcast Receivers:

Static Broadcast Receivers: These types of Receivers are declared in the manifest file and works even if the app is closed.
Dynamic Broadcast Receivers: These types of receivers work only if the app is active or minimized.

Since from API Level 26, most of the broadcast can only be caught by the dynamic receiver, so we have implemented dynamic receivers in our sample project given below. There are some static fields defined in the Intent class which can be used to broadcast different events. We have taken a change of airplane mode as a broadcast event, but there are many events for which broadcast register can be used. Following are some of the important system-wide generated intents:-

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Intent

Description Of Event

android.intent.action.BATTERY_LOW : Indicates low battery condition on the device. android.intent.action.BOOT_COMPLETED This is broadcast once after the system has finished booting android.intent.action.CALL To perform a call to someone specified by the data android.intent.action.DATE_CHANGED Indicates that the date has changed android.intent.action.REBOOT Indicates that the device has been a reboot android.net.conn.CONNECTIVITY_CHANGE The mobile network or wifi connection is changed[or reset] android.intent.ACTION_AIRPLANE_MODE_CHANGED This indicates that airplane mode has been switched on or off.

The two main things that we have to do in order to use the broadcast receiver in our application are:

Creating the Broadcast Receiver:

class AirplaneModeChangeReceiver:BroadcastReceiver[] {

override fun onReceive[context: Context?, intent: Intent?] {

// logic of the code needs to be written here

}

}

Registering a BroadcastReceiver:

IntentFilter[Intent.ACTION_AIRPLANE_MODE_CHANGED].also {

// receiver is the broadcast receiver that we have registered

// and it is the intent filter that we have created

registerReceiver[receiver,it]

}

Example

Below is the sample project showing how to create the broadcast Receiver and how to register them for a particular event and how to use them in the application.

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio.

Step 2: Working with the activity_main.xml file

Go to the activity_main.xml file and refer to the following code. Below is the code for theactivity_main.xml file.

XML

Step 3: Working with the MainActivity file

Go to the MainActivity file and refer to the following code. Below is the code for theMainActivity file. Comments are added inside the code to understand the code in more detail.

Kotlin

import android.content.Intent

import android.content.IntentFilter

import android.os.Bundle

import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity[] {

// register the receiver in the main activity in order

// to receive updates of broadcasts events if they occur

lateinit var receiver: AirplaneModeChangeReceiver

override fun onCreate[savedInstanceState: Bundle?] {

super.onCreate[savedInstanceState]

setContentView[R.layout.activity_main]

receiver = AirplaneModeChangeReceiver[]

// Intent Filter is useful to determine which apps wants to receive

// which intents,since here we want to respond to change of

// airplane mode

IntentFilter[Intent.ACTION_AIRPLANE_MODE_CHANGED].also {

// registering the receiver

// it parameter which is passed in registerReceiver[] function

// is the intent filter that we have just created

registerReceiver[receiver, it]

}

// since AirplaneModeChangeReceiver class holds a instance of Context

// and that context is actually the activity context in which

// the receiver has been created

override fun onStop[] {

super.onStop[]

unregisterReceiver[receiver]

}

Java

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.content.IntentFilter;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

AirplaneModeChangeReceiver airplaneModeChangeReceiver = new AirplaneModeChangeReceiver[];

@Override

protected void onCreate[Bundle savedInstanceState] {

super.onCreate[savedInstanceState];

setContentView[R.layout.activity_main];

}

@Override

protected void onStart[] {

super.onStart[];

IntentFilter filter = new IntentFilter[Intent.ACTION_AIRPLANE_MODE_CHANGED];

registerReceiver[airplaneModeChangeReceiver, filter];

}

@Override

protected void onStop[] {

super.onStop[];

unregisterReceiver[airplaneModeChangeReceiver];

}

Step 4: Create a new class

Go to app > java > your package name[in which the MainActicity is present] > right-click > New > Kotlin File/Class and name the files as AirplaneModeChangeReceiver. Below is the code for theAirplaneModeChangeReceiver file. Comments are added inside the code to understand the code in more detail.

Kotlin

import android.content.BroadcastReceiver

import android.content.Context

import android.content.Intent

import android.widget.Toast

// AirplaneModeChangeReceiver class extending BroadcastReceiver class

class AirplaneModeChangeReceiver : BroadcastReceiver[] {

// this function will be excecuted when the user changes his

// airplane mode

override fun onReceive[context: Context?, intent: Intent?] {

// intent contains the information about the broadcast

// in our case broadcast is change of airplane mode

// if getBooleanExtra contains null value,it will directly return back

val isAirplaneModeEnabled = intent?.getBooleanExtra["state", false] ?: return

// checking whether airplane mode is enabled or not

if [isAirplaneModeEnabled] {

// showing the toast message if airplane mode is enabled

Toast.makeText[context, "Airplane Mode Enabled", Toast.LENGTH_LONG].show[]

} else {

// showing the toast message if airplane mode is disabled

Toast.makeText[context, "Airplane Mode Disabled", Toast.LENGTH_LONG].show[]

}

Java

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.provider.Settings;

import android.widget.Toast;

public class AirplaneModeChangeReceiver extends BroadcastReceiver {

@Override

public void onReceive[Context context, Intent intent] {

if [isAirplaneModeOn[context.getApplicationContext[]]] {

Toast.makeText[context, "AirPlane mode is on", Toast.LENGTH_SHORT].show[];

} else {

Toast.makeText[context, "AirPlane mode is off", Toast.LENGTH_SHORT].show[];

}

private static boolean isAirplaneModeOn[Context context] {

return Settings.System.getInt[context.getContentResolver[], Settings.Global.AIRPLANE_MODE_ON, 0] != 0;

}

Output:

Article Tags :

Android

Kotlin

Technical Scripter

android

Technical Scripter 2020

Practice Tags :

Android

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