Question

I wrote this code in order to make a soundboard like app

public class ButtonSoundActivity extends Activity implements OnClickListener {
    private Button buttons[];
    private MediaPlayer mediaPlayers[];

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);     
    }

    @Override
    protected void onPause() {
        super.onPause();
        releaseSounds();
    }

    @Override
    protected void onResume() {
        super.onResume();
        initContent();
    }

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

    /**
     * Initialise all the content :
     * buttons, media players and set click listeners for the buttons
     */
    private void initContent() {
        buttons = new Button[5];
        mediaPlayers = new MediaPlayer[5];

        buttons[0] = (Button)findViewById(R.id.button0);
        buttons[1] = (Button)findViewById(R.id.button1);
        buttons[2] = (Button)findViewById(R.id.button2);
        buttons[3] = (Button)findViewById(R.id.button3);
        buttons[4] = (Button)findViewById(R.id.button4);

        mediaPlayers[0] = MediaPlayer.create(ButtonSoundActivity.this, R.raw.sound1);
        mediaPlayers[1] = MediaPlayer.create(ButtonSoundActivity.this, R.raw.sound2);
        mediaPlayers[2] = MediaPlayer.create(ButtonSoundActivity.this, R.raw.sound3);
        mediaPlayers[3] = MediaPlayer.create(ButtonSoundActivity.this, R.raw.sound4);
        mediaPlayers[4] = MediaPlayer.create(ButtonSoundActivity.this, R.raw.sound5);


        for(int i=0; i<5; i++) {
            buttons[i].setOnClickListener(this);
        }      
    }

    public void onClick(View v) {
        stopSounds();
        for(int i=0; i<5; i++)
            if(v.getId() == buttons[i].getId()) {
                if(mediaPlayers[i] != null)
                mediaPlayers[i].start();
            }
    }

    /**
     * Stop the previous sound when another button is clicked
     * so that the sounds don't overlap
     */
    private void stopSounds() {
        for(int i=0; i<5 ;i++)
            if(mediaPlayers[i] != null)
            if(mediaPlayers[i].isPlaying()) {
                mediaPlayers[i].pause();
                mediaPlayers[i].seekTo(0);
            }
    }

    /**
     * Release all sounds and empty the mediaPlayers array
     */
    private void releaseSounds() {
        for(int i=0; i<5;i++) {
            if(mediaPlayers[i] != null) {
                mediaPlayers[i].stop();
                mediaPlayers[i].release();
                mediaPlayers[i] = null;                 
            }
        }
    }       
}

the xml file

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

    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="button0" android:id="@+id/button0"/>

    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="button1" android:id="@+id/button1"/>

    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="button2" android:id="@+id/button2"/>      

    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="button3" android:id="@+id/button3"/>

    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="button4" android:id="@+id/button4"/>      
</LinearLayout>

The problem is that if I click a button multiple times in a row, the sound doesn’t play anymore, or sometime, when I first open the app, it crashes when I click a button.
The error says it’s related to the stopSounds method

error code

So, does anyone have an answer?

Edit: I added the if() before each mediaPlayer element to check if they are null, also I followed this method:

            AssetFileDescriptor fileDescriptor = getResources().openRawResourceFd(R.raw.sound1);
        mediaPlayers[0] = new MediaPlayer();

        try {
            mediaPlayers[0].setDataSource(fileDescriptor.getFileDescriptor());
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            mediaPlayers[0].prepare();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

but without any luck 🙁

Edit 2: I got it working 🙂 , I just had to make sure that the mediaPlayer array is empty when I restart the app. Also I added the onPause() and onResume() functions.

Answer 1

You are getting a NullPointerException at line 57, inside your stopSounds method. Could you post this line all by itself?

Most likely one of the objects in mediaPlayers is null. Try stepping through the debugger and see what the array looks like when you first enter the stopSounds method.