AudioPlayer close() NullPointerException

Core Library Questions

lady_viol..

AudioPlayer close() NullPointerException

in Core Library Questions • 2 years ago

Hi guys,
I'm new of processing... I've to use AudioPlayer to play a song to a specific output, but I have a problem, I cant close the AudioPlayer after I have played a song

import ddf.minim.*;

Minim minim;
AudioPlayer groove;
void setup()
{
size(512, 200, P3D);
minim = new Minim(this);
groove = minim.loadFile("D:\\Music\\Musica\\11.mp3", 2048);
}
void draw()
{
background(0);
}
void keyPressed()
{
if ( key == 'p' ) groove.play();
if ( key == 's' ) stop();
}
void stop()
{
// always close Minim audio classes when you are done with them
groove.close();
// always stop Minim before exiting.
minim.stop();
super.stop();
}

In this code, when i stop the audioPlayer I keep this error:

processing.app.debug.RunnerException: NullPointerException
    at processing.app.Sketch.placeException(Sketch.java:1543)
    at processing.app.debug.Runner.findException(Runner.java:582)
    at processing.app.debug.Runner.reportException(Runner.java:558)
    at processing.app.debug.Runner.exception(Runner.java:498)
    at processing.app.debug.EventThread.exceptionEvent(EventThread.java:367)
    at processing.app.debug.EventThread.handleEvent(EventThread.java:255)
    at processing.app.debug.EventThread.run(EventThread.java:89)
Exception in thread "Animation Thread" java.lang.NullPointerException
    at ddf.minim.javasound.JSBaseAudioRecordingStream.close(JSBaseAudioRecordingStream.java:407)
    at ddf.minim.AudioSource.close(AudioSource.java:99)
    at sketch_mar03a.stop(sketch_mar03a.java:51)
    at processing.core.PApplet.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:619)

How can I close the AudioPlayer? Where am I wrong?

Replies(3)

anchnk

Re: AudioPlayer close() NullPointerException

2 years ago

Hi & welcome,

Basically there's nothing wrong with your code.
And i'm sure most people getting started would wrote the same code.
So, what's the hell ?

You got that exception because your using event (keyboard strokes) to play or stop sound.
There's nothing wrong doing that but you have to add another line to check that AudioPlayer object (the one you called groove) is actually something.

If we look at the stacktrace, the exception occurs when you call the stop() function.
And in detail it occurs when the program call the close() method from the AudioPlayer object at the line.

groove.close();

You got a null pointer exception. That means your AudioPlayer object is null (not ready to be manipulated, there's just nothing in it) when you try to call is close() method.

To get it sorted, just be sure that the AudioPlayer object isn't null before trying to close() it.
Like :

if (groove != null) {
groove.close();
}
...

The ... is the rest of your program.

You can find similar example in the minim documentation.

I hope i'm not confusing.

lady_viol..

Re: AudioPlayer close() NullPointerException

2 years ago

I added the control

if (groove != null) {
groove.close();
}

But I have the same problem... :(

anchnk

Re: AudioPlayer close() NullPointerException

2 years ago

Oh my bad sorry, i think i just got a work overload today and was confused.
The NPE is caused because the stop function is called twice (you call it when you press the key, and then the program try to stop because it's what happens when the sketch needs to stop by default).

Maybe change the stop() name to something else (like stopMinim()) should avoid that.
Or maybe adding exit(); at the end of the stop() method) so that the program exit before stop is calling once again.

Not sure that's the best solution, as i said i'm a bit confused.

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