无法设置音量，音量控制未转发到系统

我尝试使用安卓MediaPlayer框架来发挥mp3 file (看到这个问题).

在我设法使其工作后，我很快意识到，音量增大/减小事件被类捕获javafxports.android.KeyEventProcessor并且永远不会被转发。我试图规避这一点，但没有成功。

是否有任何方法可以将事件分派到发生该事件的系统not被抓住？

感谢致敬， 丹尼尔

虽然我讨厌不断地回答自己的问题，但在玩了几个小时的 Android API、挖掘一些文档等等之后，我找到了一个解决方案。

我的解决方案部分基于 @josé-pereda 就该主题给出的答案《javafxports如何调用android原生媒体播放器》.

我为任务创建了一个界面“volumeUp", "音量减小" and "mute":

public interface NativeVolumeService {
    void volumeUp();
    void volumeDown();
    void mute();
}

然后，根据以下关于如何设置的答案Android 上的系统音量，我在Android上想出了以下实现：

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);
        }
    }
}

为了集成它，我在我的主类中创建了适当的实例（我全局需要这个实例 - 你会看到为什么）

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是一个类变量。

然后我在我的上注册了一个事件处理程序Stages Scene:

@Override
public void start(Stage stage) throws Exception {
    // initiate everything
    scene.addEventFilter(KeyEvent.ANY, this::handleGlobalKeyEvents);
    // do more stuff, if needed
}

最后，方法handleGlobalKeyEvents看起来像这样：

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();
        }
    }
}

最后，解决方案非常干净，而且不太复杂。只是直到它起作用的方式有点令人讨厌。

@JoséPereda：如果您想将此解决方案集成为魅力下降插件等，请随意，但如果您这样做，那么很高兴被提及和通知。

问候， 丹尼尔