Android w/ Java: Using Seekbar to adjust volume

Question

I'm new to Android App development (on android studio) and to start off I'm creating a simple 'bonk' soundboard app, and testing it using the Pixel 2 android emulator. The goal of the app is to play the bonk noise whenever someone presses the BONK button on my main screen. I also wanted to implement a seekbar that adjusts the volume when you slide it. To do this I followed a simple implementation I found here on StackOverflow (shown below).

Even though the rest of my app works fine, for some reason my volume won't adjust whenever I slide the seekbar. Here is my code:

MainActivity.java

package com.example.bonk;

import androidx.appcompat.app.AppCompatActivity;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;

public class MainActivity extends AppCompatActivity {

    Button bonkButton;
    SeekBar volumeSeekBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bonkButton = (Button)findViewById(R.id.bonkButton);
        volumeSeekBar = (SeekBar)findViewById(R.id.volumeSeekBar);

        final MediaPlayer mp = MediaPlayer.create(this, R.raw.bonksound);
        bonkButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mp.start();
            }
        });
    }
}

Volumizer.java

package com.example.bonk;

import android.app.Activity;
import android.content.Context;
import android.media.AudioManager;
import android.os.Bundle;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

public class Volumizer extends Activity {
    //Called when the activity is first created.
    private SeekBar volumeSeekbar = null;
    private AudioManager audioManager = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setVolumeControlStream(AudioManager.STREAM_MUSIC);
        setContentView(R.layout.activity_main);
        initControls();
    }

    private void initControls() {
        try {
            volumeSeekbar = findViewById(R.id.volumeSeekBar);
            audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
            volumeSeekbar.setMax(audioManager
                    .getStreamMaxVolume(AudioManager.STREAM_MUSIC));
            volumeSeekbar.setProgress(audioManager
                    .getStreamVolume(AudioManager.STREAM_MUSIC));

            volumeSeekbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
                @Override
                public void onStopTrackingTouch(SeekBar arg0) {
                }

                @Override
                public void onStartTrackingTouch(SeekBar arg0) {
                }

                @Override
                public void onProgressChanged(SeekBar arg0, int progress, boolean arg2) {
                    audioManager.setStreamVolume(AudioManager.STREAM_MUSIC,
                            progress, 0);
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Activity_main.xml

<?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">

    <Button
        android:id="@+id/bonkButton"
        android:layout_width="296dp"
        android:layout_height="232dp"
        android:text="@string/bonk"
        android:textSize="30sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <SeekBar
        android:id="@+id/volumeSeekBar"
        android:layout_width="276dp"
        android:layout_height="26dp"
        android:layout_marginBottom="116dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.496"
        app:layout_constraintStart_toStartOf="parent" />


</androidx.constraintlayout.widget.ConstraintLayout>

Please let me know if you have any ideas as of what I may be doing wrong. Thank you!

Answer 1

I was able to solve the problem by moving my initControls() function definition into my MainActivity.java class and calling it onCreate.