Application that uses audio mode

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-permission android:name="android.permission.VIBRATE" />

    <application
    ....
    </application>
</manifest>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn_normal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Normal" />

    <Button
        android:id="@+id/btn_silent"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Silent" />

    <Button
        android:id="@+id/btn_vibrate"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Vibrate" />

</LinearLayout>

package com.example.myapplication;

import android.content.Context;
import android.media.AudioManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private Button btnNormal;
    private Button btnSilent;
    private Button btnVibrate;
    private AudioManager audioManager;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
        btnNormal = findViewById(R.id.btn_normal);
        btnSilent = findViewById(R.id.btn_silent);
        btnVibrate = findViewById(R.id.btn_vibrate);
        
        btnNormal.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                audioManager.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
            }
        });
        
        btnSilent.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                audioManager.setRingerMode(AudioManager.RINGER_MODE_SILENT);
            }
        });
        
        btnVibrate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                audioManager.setRingerMode(AudioManager.RINGER_MODE_VIBRATE);
            }
        });
    }
}