Implementing Audiotrack Class in Static mode

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I’m trying to do in app very simple so I learn to implement the Audiotrack class (android.media.AudioTrack).
The app is just a screen with a button, which when pressed should play a file . wav of 1seg. The app installs smoothly in the emulator, but when I click the button to play the sound, it gives error.
My implementation of audioTrack is correct? 

//MainActivity

public class MainActivity extends Activity{

    private DrumKit dk = new DrumKit();

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

    public void onClick(View v) { 
        dk.playAudio();
    } 

}

//Classe para executar o audio:

public class DrumKit {

     byte[] byteData = null;
     private File file = null; 
     private AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
            AudioFormat. CHANNEL_OUT_MONO,
            AudioFormat.ENCODING_PCM_16BIT, 88200,
            AudioTrack.MODE_STATIC );

     public void playAudio(){

         file = new File(Environment.getExternalStorageDirectory(), "snare.wav");
         byteData = new byte[(int) file.length()];

         audioTrack.play();
         audioTrack.write(byteData, 0, byteData.length); 
         audioTrack.stop();
         audioTrack.release();
     }
}

//Logcat:

06-05 10:23:01.131: D/gralloc_goldfish(1381): Emulator without GPU emulation detected.
06-05 10:23:14.371: D/AndroidRuntime(1381): Shutting down VM
06-05 10:23:14.371: W/dalvikvm(1381): threadid=1: thread exiting with uncaught exception (group=0xb1a1eba8)
06-05 10:23:14.451: E/AndroidRuntime(1381): FATAL EXCEPTION: main
06-05 10:23:14.451: E/AndroidRuntime(1381): Process: com.example.airdrums, PID: 1381
06-05 10:23:14.451: E/AndroidRuntime(1381): java.lang.IllegalStateException: Could not execute method of the activity
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.view.View$1.onClick(View.java:3823)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.view.View.performClick(View.java:4438)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.view.View$PerformClick.run(View.java:18422)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at     android.os.Handler.handleCallback(Handler.java:733)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.os.Handler.dispatchMessage(Handler.java:95)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.os.Looper.loop(Looper.java:136)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.app.ActivityThread.main(ActivityThread.java:5017)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at java.lang.reflect.Method.invokeNative(Native Method)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at java.lang.reflect.Method.invoke(Method.java:515)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at dalvik.system.NativeStart.main(Native Method)
06-05 10:23:14.451: E/AndroidRuntime(1381): Caused by: java.lang.reflect.InvocationTargetException
06-05 10:23:14.451: E/AndroidRuntime(1381):     at java.lang.reflect.Method.invokeNative(Native Method)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at java.lang.reflect.Method.invoke(Method.java:515)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.view.View$1.onClick(View.java:3818)
06-05 10:23:14.451: E/AndroidRuntime(1381):     ... 11 more
06-05 10:23:14.451: E/AndroidRuntime(1381): Caused by: java.lang.IllegalStateException: play() called on uninitialized AudioTrack.
06-05 10:23:14.451: E/AndroidRuntime(1381):     at android.media.AudioTrack.play(AudioTrack.java:984)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at com.example.airdrums.DrumKit.playAudio(DrumKit.java:25)
06-05 10:23:14.451: E/AndroidRuntime(1381):     at com.example.airdrums.MainActivity.onClick(MainActivity.java:51)
06-05 10:23:14.451: E/AndroidRuntime(1381):     ... 14 more
android

  • @Andrecsimoes, is the fact that giving stop/release soon after giving play does not cause problems (even if it is 1 second)? It is not worth testing

  • @Wakin I’ve tried to comment on the stop and release, but it didn’t work!

  • logcat indicates that Audiotrack has not been initialized correctly. Check which state of Audiotrack through: audioTrack.getState();. More info on Audiostack

  • Just one question... Did you happen to declare the two public classes in the same file? Or did you just put them together here in your question? A source file cannot have two public classes.

1 answer

1

At the startup of your AudioTrack has a space in an argument. Look closely:

private AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
            AudioFormat. CHANNEL_OUT_MONO,
            AudioFormat.ENCODING_PCM_16BIT, 88200,
            AudioTrack.MODE_STATIC );

The argument AudioFormat. CHANNEL_OUT_MONO is with a space after the point, remove this space. Another thing I realized is that in the class documentation AudioTrack concerning the method play(), says the following:

Starts playing an Audiotrack. If track’s Creation mode is MODE_STATIC, you must have called write() prior.

Translating...

Starts playback of an Audiotrack. If the track creation mode is MODE_STATIC, you should call write() before.

As your way of creating the track there is MODE_STATIC, then reverse the lines:

audioTrack.play();
audioTrack.write(byteData, 0, byteData.length);

The write method has to be called before the play(). See if this solves.

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