Source Code of MainAcivity.java

import androidx.appcompat.app.AppCompatActivity;

import android.os.BatteryManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button showstatus = (Button) findViewById(R.id.showstatus);
        showstatus.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                BatteryManager bm = (BatteryManager)getSystemService(BATTERY_SERVICE);

                    int percentage = 0;
                    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
                        percentage = bm.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);
                    }
                    Toast.makeText(getApplicationContext(),"Battery Percentage is " + percentage + " %",Toast.LENGTH_LONG).show();


            }
        });

    }
}

Source Code of activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".workingwithbattery" >

    <Button
        android:id="@+id/showstatus"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Show Status" android:layout_marginTop="30dp"
        android:layout_marginLeft="30dp"
        android:layout_marginRight="30dp"
        />

</LinearLayout>

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