Try to set MediaPlayer - error `Attempt to invoke virtual method`

[salvonos]

I am trying to connect the visualiser with a music player from MainActivity.java. The visualiser is set in a fragment and all works well when I call it showing it in the activity however, overtime I try to add the MusicPlayer i get the error:

java.lang.RuntimeException: Unable to start activity ComponentInfo{example.it/example.it.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.media.MediaPlayer.getCurrentPosition()' on a null object reference
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3253)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3349)
                      at android.app.ActivityThread.access$1100(ActivityThread.java:221)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:158)
                      at android.app.ActivityThread.main(ActivityThread.java:7224)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.media.MediaPlayer.getCurrentPosition()' on a null object reference
                      at example.it.AudioVisualizationFragment.onViewCreated(AudioVisualizationFragment.java:60)
                      at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1127)
                      at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
                      at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
                      at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
                      at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
                      at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:604)
                      at example.it.MainActivity.onStart(MainActivity.java:1210)

I have called the music player from MusicService.java

AudioVisualizationFragment.java

audioVisualization = (AudioVisualization) view;
        audioVisualization.linkTo(DbmHandler.Factory.newVisualizerHandler(getContext(), MusicService.mPlayer));

MainActivity.java

private void openFragment() {
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.audio_player_lyt, AudioVisualizationFragment.newInstance())
                .commit();

    }

How could I solve this error?

[Iojjj]

According to the logs, your MediaPlayer instance equals null. Check your AudioVisualizationFragment on line 60. This crash doesn't related to library.

P.S. Do not use static variables for holding a MediaPlayer instance.

[salvonos]

Thank you for your quick replay. I understand that the value is null but If I don't use static variables how could I send the audio from mediaPlayer to the fragment?

[Iojjj]

@salvonos. MediaPlayer is not required for visualizer handler. You can pass audio session ID instead. There are several ways to communicate with service:

• bind to service and retrieve instance of MediaPlayer or audioSessionId;
• use BroadcastReceiver to get audioSessionId;

[salvonos]

Thanks I will try this. I have also tried to use "0" as session ID which should corresponds to the audio output mix? However, not animation is received

[salvonos]

I have tried almost everything but cannot work it out. I have tried to start the media player direct into the fragment but the visualiser is not animating:

mediaPlayer = MediaPlayer.create(getContext(), R.raw.sound);
        mediaPlayer.start();
        audioVisualization.linkTo(DbmHandler.Factory.newVisualizerHandler(context, mediaPlayer));

[Iojjj]

Have you checked Troubleshooting section in Readme? It's possible that visualizer will not work on some devices. What device are you using?

[salvonos]

I am using Samsung Galaxy S5. I can see the visualiser but not animating