I tried to use the Android MediaPlayer framework to play a mp3 file
(see this question).
After I managed to make it work, I quickly recognized, that the volume up/down events are caught by the class javafxports.android.KeyEventProcessor and never get forwarded. I tried to circumvent that, but to no avail.
Are there any means to dispatch the event to the system where it not gets caught?
Thanks and regards, Daniel
While I hate to constantly answer my own questions, I found a solution after a couple of hours playing with the Android API, digging through some documentations and so on.
My solution is partially based the answer, given by @josé-pereda on the topic "javafxports how to call android native Media Player".
I created an interface for the tasks "volumeUp", "volumeDown" and "mute":
public interface NativeVolumeService {
void volumeUp();
void volumeDown();
void mute();
}
Then, based on the following answer on how to set the system volume on Android, I came up with the following implementation on Android:
import java.util.ArrayList;
import java.util.logging.Logger;
import android.content.Context;
import android.media.AudioManager;
import android.view.KeyEvent;
import android.view.View;
import android.view.ViewGroup;
import my.package.platform.NativeVolumeService;
import javafxports.android.FXActivity;
public class NativeVolumeServiceAndroid implements NativeVolumeService {
private static final Logger LOG = Logger.getLogger(NativeVolumeServiceAndroid.class.getName());
private final AudioManager audioManager;
private final int maxVolume;
private int preMuteVolume = 0;
private int currentVolume = 0;
public NativeVolumeServiceAndroid() {
audioManager = (AudioManager) FXActivity.getInstance().getSystemService(Context.AUDIO_SERVICE);
maxVolume = audioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
}
@Override
public void volumeUp() {
LOG.info("dispatch volume up event");
KeyEvent event = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_VOLUME_UP);
dispatchEvent(event, true, false);
}
@Override
public void volumeDown() {
LOG.info("dispatch volume down event");
KeyEvent event = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_VOLUME_DOWN);
dispatchEvent(event, false, false);
}
@Override
public void mute() {
LOG.info("dispatch volume mute event");
KeyEvent event = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_VOLUME_MUTE);
dispatchEvent(event, false, true);
}
private void dispatchEvent(KeyEvent event, boolean up, boolean mute) {
// hardware key events (amongst others) get caught by the JavaFXPorts engine (or better: the Dalvik impl from Oracle)
// to circumvent this, we need to do the volume adjustment the hard way: via the AudioManager
// see: https://developer.android.com/reference/android/media/AudioManager.html
// see: https://stackoverflow.com/questions/9164347/setting-the-android-system-volume?rq=1
// reason:
// FXActivity registers a FXDalvikEntity, which etends the surface view and passing a key processor
// called KeyEventProcessor - this one catches all key events and matches them to JavaFX representations.
// Unfortunately, we cannot bypass this, so we need the AudioManager
currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
if (mute) {
if (currentVolume > 0) {
preMuteVolume = currentVolume;
audioManager.adjustStreamVolume(AudioManager.STREAM_MUSIC, AudioManager.ADJUST_SAME,
AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE | AudioManager.FLAG_SHOW_UI);
} else {
preMuteVolume = 0;
audioManager.adjustStreamVolume(AudioManager.STREAM_MUSIC, preMuteVolume, AudioManager.FLAG_SHOW_UI);
}
} else if (up) {
audioManager.adjustStreamVolume(AudioManager.STREAM_MUSIC,
(currentVolume + 1) <= maxVolume ? AudioManager.ADJUST_RAISE : AudioManager.ADJUST_SAME, AudioManager.FLAG_SHOW_UI);
} else if (!up) {
audioManager.adjustStreamVolume(AudioManager.STREAM_MUSIC,
(currentVolume - 1) >= 0 ? AudioManager.ADJUST_LOWER : AudioManager.ADJUST_SAME, AudioManager.FLAG_SHOW_UI);
}
}
}
to integrate it, I created the appropriate instance in my main class (I need this globally - you will see, why)
private void instantiateNativeVolumeService() {
String serviceName = NativeVolumeService.class.getName();
if (Platform.isDesktop()) {
serviceName += "Desktop";
} else if (Platform.isAndroid()) {
serviceName += "Android";
}
try {
volumeService = (NativeVolumeService) Class.forName(serviceName).newInstance();
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
LOG.log(Level.SEVERE, "Could not get an instance of NativeAudioService for platform " + Platform.getCurrent(), e);
}
}
volumeService is a class variable.
Then I registered an event handler on my Stages Scene:
@Override
public void start(Stage stage) throws Exception {
// initiate everything
scene.addEventFilter(KeyEvent.ANY, this::handleGlobalKeyEvents);
// do more stuff, if needed
}
And finally, the method handleGlobalKeyEvents looks like this:
private void handleGlobalKeyEvents(KeyEvent event) {
// use a more specific key event type like
// --> KeyEvent.KEY_RELEASED == event.getEventType()
// --> KeyEvent.KEY_PRESSED == event.getEventType()
// without it, we would react on both events, thus doing one operation too much
if (event.getCode().equals(KeyCode.VOLUME_UP) && KeyEvent.KEY_PRESSED == event.getEventType()) {
if (volumeService != null) {
volumeService.volumeUp();
event.consume();
}
}
if (event.getCode().equals(KeyCode.VOLUME_DOWN) && KeyEvent.KEY_PRESSED == event.getEventType()) {
if (volumeService != null) {
volumeService.volumeDown();
event.consume();
}
}
}
In the end, the solution is as clean as it gets and not too complicated. Only the way until it worked was a bit nasty.
@JoséPereda: If you want to integrate this solution as a charm down plugin or so, please feel free, but it would be nice to be mentioned and notified, if you do.
Regards, Daniel