某些 Android 应用程序会在设备音量发生变化时生成通知,有些应用程序会锁定音量。 对于我的一生,我无法弄清楚这是如何做到的。 请问有人可以帮我举个例子吗?
实际上有一种方法可以在服务中使用 Content Observer。它的工作原理就像一个广播接收器,监听音量、联系人、通话记录等内容变化的事件...
在您的服务中使用以下代码
public class VolumeService extends Service{
AudioManager mAudioManager;
Handler mHandler;
private ContentObserver mVolumeObserver = new ContentObserver(mHandler) {
@Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
if (mAudioManager != null) {
final int volume = mAudioManager.getStreamVolume(AudioManager.STREAM_RING);
System.out.println("Volume: " + volume);
}
}
};
@Override
public void onCreate() {
super.onCreate();
System.out.println("Volume Service started");
mAudioManager = (AudioManager) getSystemService(AUDIO_SERVICE);
//As of API 23, this approach ostensibly no longer works:
//Uri uri = Settings.System.getUriFor(Settings.System.VOLUME_SETTINGS[AudioManager.STREAM_RING]);
Uri uri = Settings.System.CONTENT_URI; //<-- This approach seems to be stable across versions, although will theoretically trigger onChange() during more types of system changes.
getContentResolver().registerContentObserver(uri, true, mVolumeObserver);
System.out.println("Volume listener registered.");
}
@Override
public void onDestroy() {
super.onDestroy();
System.out.println("Volume service ended.");
getContentResolver().unregisterContentObserver(mVolumeObserver);
}
@Override
public IBinder onBind(Intent arg0) {
return null;
}
}
不要忘记在 Android Manifest.xml 中声明它
<service android:name=".service.VolumeService" >
没有广播操作来检测音量变化,但您可能可以每隔一两秒检查一下音量是多少
getStreamVolume
如果您需要将其锁定在特定音量,则每隔一两秒使用:setStreamVolume
查看 http://developer.android.com/reference/android/media/AudioManager.htm 了解更多信息。
您可以使用 AlarmManager 类或处理程序每秒左右检查一次音量。
如果是活动,您可以覆盖
onKeyDown
来检测按键操作。请参阅 http://developer.android.com/reference/android/view/View.html
您可以使用辅助功能服务捕获音量/硬件按键事件。
这是一种方法,您可以固定到设定的音量而不是更改。我的目标是调整系统音量服务。
此外,避免仅在需要时才这样做。
public class VolumeKeyController {
private MediaSessionCompat mMediaSession;
private final Context mContext;
public VolumeKeyController(Context context) {
mContext = context;
}
private void createMediaSession() {
mMediaSession = new MediaSessionCompat(mContext, KeyUtil.log);
mMediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
mMediaSession.setPlaybackState(new Builder()
.setState(PlaybackStateCompat.STATE_PLAYING, 0, 0)
.build());
mMediaSession.setPlaybackToRemote(getVolumeProvider());
mMediaSession.setActive(true);
}
private VolumeProviderCompat getVolumeProvider() {
final AudioManager audio = mContext.getSystemService(Context.AUDIO_SERVICE);
int STREAM_TYPE = AudioManager.STREAM_MUSIC;
int currentVolume = audio.getStreamVolume(STREAM_TYPE);
int maxVolume = audio.getStreamMaxVolume(STREAM_TYPE);
final int VOLUME_UP = 1;
final int VOLUME_DOWN = -1;
return new VolumeProviderCompat(VolumeProviderCompat.VOLUME_CONTROL_RELATIVE, maxVolume, currentVolume) {
@Override
public void onAdjustVolume(int direction) {
// Up = 1, Down = -1, Release = 0
// Replace with your action, if you don't want to adjust system volume
if (direction == VOLUME_UP) {
audio.adjustStreamVolume(STREAM_TYPE,
AudioManager.ADJUST_RAISE, AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE);
}
else if (direction == VOLUME_DOWN) {
audio.adjustStreamVolume(STREAM_TYPE,
AudioManager.ADJUST_LOWER, AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE);
}
setCurrentVolume(audio.getStreamVolume(STREAM_TYPE));
}
};
}
// Call when control needed, add a call to constructor if needed immediately
public void setActive(boolean active) {
if (mMediaSession != null) {
mMediaSession.setActive(active);
return;
}
createMediaSession();
}
// Call from Service's onDestroy method
public void destroy() {
if (mMediaSession != null) {
mMediaSession.release();
}
}
}