Broadcast

Manifest File

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

  package="com.example.broadcastreceiver">

  <application

    android:allowBackup="true"

    android:icon="@mipmap/ic_launcher"

    android:label="@string/app_name"

    android:roundIcon="@mipmap/ic_launcher_round"

    android:supportsRtl="true"

    android:theme="@style/AppTheme">

    <activity android:name=".MainActivity">

      <intent-filter>

        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.LAUNCHER" />

      </intent-filter>

    </activity>

    <receiver

      android:name=".MyReceiver"

      android:exported="true">

      <intent-filter>

        <action android:name="android.intent.action.BATTERY LOW" />

      </intent-filter>

    </receiver>

  </application>

</manifest>

XML File

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"

  xmlns:app="http://schemas.android.com/apk/res-auto"

  xmlns:tools="http://schemas.android.com/tools"

  android:layout_width="match_parent"

  android:layout_height="match_parent"

  tools:context=".MainActivity">

  <TextView

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:text="Hello World!"

    app:layout_constraintBottom_toBottomOf="parent"

    app:layout_constraintLeft_toLeftOf="parent"

    app:layout_constraintRight_toRightOf="parent"

    app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Java File

package com.example.broadcastreceiver;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

  @Override

  protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

  }

}

MyReceiver.java 

package com.example.broadcastreceiver;

import android.content.BroadcastReceiver;

import android.content.Intent;

import android.widget.Toast;

import android.content.Context;

public class MyReceiver extends BroadcastReceiver {

  @Override

  public void onReceive(Context context, Intent intent){

    Toast.makeText(context,"Battery is low,recharge it",Toast.LENGTH_LONG).show();

  }

}