Get Battery Percentage Using Broadcast Receiver In Android

Create your android app named as BatterPercentageDemo.

Add TextView in MainActivity Layout File

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<?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:id="@+id/tvBattery"
        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>

Create BatteryReceiver Java Class

Creae BatteryReceiver java class and extends it by BroadcastReceiver.

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public class BatteryReceiver extends BroadcastReceiver {

    TextView tv;
    BatteryReceiver(TextView tv){
        this.tv = tv;
    }
    @Override
    public void onReceive(Context context, Intent intent) {
        int batteryPercentage = intent.getIntExtra("level", 0);
        if(batteryPercentage != 0){
            tv.setText(batteryPercentage + "%");
        }
    }
}

Override the onReceive method and use the Intent to get the battery level.

Register Broadcast Receiver Programmatically In MainActivity Class

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public class MainActivity extends AppCompatActivity {

    BatteryReceiver batteryReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView tv = (TextView)findViewById(R.id.tvBattery);

        batteryReceiver = new BatteryReceiver(tv);
        registerReceiver(batteryReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    }

    @Override
    protected void onStop() {
        super.onStop();
        unregisterReceiver(batteryReceiver);
    }
}

We have created the object of BatteryReceiver class and pass the TextView object in the constructor.
Use registerReceiver method to regsiter your batteryReceiver class with Intent Action ACTION_BATTERY_CHANGED.

Unregsiter Broadcast Receiver

Unregister your broadcast receiver class object batteryReceiver in onStop method.

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 @Override
    protected void onStop() {
        super.onStop();
        unregisterReceiver(batteryReceiver);
    }

If you get below error while building you application:
One or more issues found when checking AAR metadata values:

The minCompileSdk (31) specified in a
dependency’s AAR metadata (META-INF/com/android/build/gradle/aar-metadata.properties)
is greater than this module’s compileSdkVersion (android-30).
Dependency: androidx.appcompat:appcompat:1.4.0.

Fix: update the compileSdk and targetSdk to 31 in build.gradle file.

Now, connect your android phone and run the app there. It will show the battery percentage in the app.