Почему mediaPlayer.stop(); тут не работает?

[В ВИДЕ] Я загрузил два звука, которые могут воспроизводиться и перекрываться без проблем, однако я не могу их остановить или приостановить.

В своем текущем состоянии кнопка «Стоп» только записывает в журнал, но я не могу получить mediaplayer.stop(); или медиаплеер.пауза(); работать.

Чтобы было ясно, я хочу, чтобы stopSound заканчивал все звуки, воспроизводимые в данный момент, и чтобы каждый звук начинался с начала при повторном вызове.

VolumeControl создает конфликт? Я что-то упускаю? Любая помощь приветствуется.

MainActivity.java

public class MainActivity extends AppCompatActivity {

    public MediaPlayer mediaPlayer;
    AudioManager audioManager;

    public void playSound(View view) {

        Button soundButton = (Button) view;

        Log.i("INFO", soundButton.getTag().toString() + " button pressed.");

        MediaPlayer mediaPlayer = MediaPlayer.create(this, getResources().getIdentifier(soundButton.getTag().toString(), "raw", getPackageName()));

        mediaPlayer.start();

    }

    public void stopSound(View view) {

        Log.i("INFO", "stop button pressed.");   

        mediaPlayer.stop();

    }

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

        audioManager = (AudioManager) getSystemService(AUDIO_SERVICE);

        int maxVolume = audioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
        int currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);

        mediaPlayer = MediaPlayer.create(this, R.raw.sound_01);

        mediaPlayer = MediaPlayer.create(this, R.raw.sound_02);

        SeekBar volumeControl = (SeekBar) findViewById(R.id.seekBar);

        volumeControl.setMax(maxVolume);
        volumeControl.setProgress(currentVolume);

        volumeControl.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {

                Log.i("Seekbar changed", Integer.toString(i));

                audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, i, 0);

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });

    }

Activity_main.xml

<?xml version = "1.0" encoding = "utf-8"?>
<android.support.constraint.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"
    android:background = "@android:color/background_light"
    tools:context = "com.example.company.app.MainActivity">

    <android.support.constraint.ConstraintLayout
        android:id = "@+id/constraintLayout"
        android:layout_width = "match_parent"
        android:layout_height = "match_parent"
        app:layout_constraintBottom_toBottomOf = "parent"
        app:layout_constraintEnd_toEndOf = "parent"
        app:layout_constraintStart_toStartOf = "parent"
        app:layout_constraintTop_toTopOf = "parent">

        <ScrollView
            android:id = "@+id/scrollView"
            android:layout_width = "match_parent"
            android:layout_height = "match_parent"
            android:layout_marginBottom = "128dp"
            android:layout_marginTop = "64dp"
            app:layout_constraintBottom_toBottomOf = "parent"
            app:layout_constraintEnd_toEndOf = "parent"
            app:layout_constraintStart_toStartOf = "parent"
            app:layout_constraintTop_toTopOf = "parent">

            <GridLayout
                android:id = "@+id/gridLayout"
                android:layout_width = "match_parent"
                android:layout_height = "wrap_content"
                android:background = "@android:color/black"
                android:columnCount = "2"
                android:paddingBottom = "4dp"
                android:paddingTop = "4dp"
                app:layout_constraintBottom_toBottomOf = "parent"
                app:layout_constraintEnd_toEndOf = "parent"
                app:layout_constraintStart_toStartOf = "parent"
                app:layout_constraintTop_toTopOf = "parent">

                <Button
                    android:id = "@+id/buttonL1"
                    android:layout_columnWeight = "1"
                    android:layout_gravity = "center_vertical"
                    android:layout_marginLeft = "6dp"
                    android:layout_marginRight = "1dp"
                    android:layout_rowWeight = "1"
                    android:onClick = "playSound"
                    android:tag = "sound_01"
                    android:text = "Sound One" />

                <Button
                    android:id = "@+id/buttonR1"
                    android:layout_columnWeight = "1"
                    android:layout_gravity = "center_vertical"
                    android:layout_marginLeft = "1dp"
                    android:layout_marginRight = "6dp"
                    android:layout_rowWeight = "1"
                    android:onClick = "playSound"
                    android:tag = "sound_02"
                    android:text = "Sound Two" />


            </GridLayout>
        </ScrollView>

        <SeekBar
            android:id = "@+id/seekBar"
            android:layout_width = "0dp"
            android:layout_height = "wrap_content"
            android:layout_marginEnd = "24dp"
            android:layout_marginStart = "24dp"
            android:layout_marginTop = "16dp"
            app:layout_constraintEnd_toEndOf = "parent"
            app:layout_constraintStart_toStartOf = "parent"
            app:layout_constraintTop_toBottomOf = "@+id/scrollView" />

        <Button
            android:id = "@+id/stopButton"
            android:layout_width = "0dp"
            android:layout_height = "0dp"
            android:layout_marginTop = "16dp"
            android:onClick = "stopSound"
            android:text = "stop"
            app:layout_constraintBottom_toBottomOf = "parent"
            app:layout_constraintEnd_toEndOf = "parent"
            app:layout_constraintStart_toStartOf = "parent"
            app:layout_constraintTop_toBottomOf = "@id/seekBar" />

    </android.support.constraint.ConstraintLayout>

</android.support.constraint.ConstraintLayout>