声音的类型有：定义在AudioSystem.java文件中
/* The default audio stream */ public static final int STREAM_DEFAULT = -1; /* The audio stream for phone calls */ public static final int STREAM_VOICE_CALL = 0; /* The audio stream for system sounds */ public static final int STREAM_SYSTEM = 1; /* The audio stream for the phone ring and message alerts */ public static final int STREAM_RING = 2; /* The audio stream for music playback */ public static final int STREAM_MUSIC = 3; /* The audio stream for alarms */ public static final int STREAM_ALARM = 4; /* The audio stream for notifications */ public static final int STREAM_NOTIFICATION = 5; /* @hide The audio stream for phone calls when connected on bluetooth */ public static final int STREAM_BLUETOOTH_SCO = 6; /* @hide The audio stream for enforced system sounds in certain countries (e.g camera in Japan) */ public static final int STREAM_SYSTEM_ENFORCED = 7; /* @hide The audio stream for DTMF tones */ public static final int STREAM_DTMF = 8; /* @hide The audio stream for text to speech (TTS) */ public static final int STREAM_TTS = 9;正常情况下在音、视频界面调节音量调节的Stream是STREAM_MUSIC，回到Luncher调节的是STREAM_VOICE_CALL，但这个切换有点延迟StreamOverride.sDelayMs，导致退出音、视频界面后马上调节，改变的还是STREAM_MUSIC的大小，如图所示：
可以修改/frameworks/base/media/java/android/media/AudioService.java文件
/**
* For code clarity for getActiveStreamType(int)
* @param delay_ms max time since last STREAM_MUSIC activity to consider
* @return true if STREAM_MUSIC is active in streams handled by AudioFlinger now or
* in the last "delay_ms" ms.
*/
private boolean isAfMusicActiveRecently(int delay_ms) {
return AudioSystem.isStreamActive(AudioSystem.STREAM_MUSIC, delay_ms)
|| AudioSystem.isStreamActiveRemotely(AudioSystem.STREAM_MUSIC, delay_ms);
}
private int getActiveStreamType(int suggestedStreamType) {
switch (mPlatformType) {
case PLATFORM_VOICE:
if (isInCommunication()) {
if (AudioSystem.getForceUse(AudioSystem.FOR_COMMUNICATION)
== AudioSystem.FORCE_BT_SCO) {
// Log.v(TAG, "getActiveStreamType: Forcing STREAM_BLUETOOTH_SCO...");
return AudioSystem.STREAM_BLUETOOTH_SCO;
} else {
// Log.v(TAG, "getActiveStreamType: Forcing STREAM_VOICE_CALL...");
return AudioSystem.STREAM_VOICE_CALL;
}
} else if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {
if (isAfMusicActiveRecently(StreamOverride.sDelayMs)) {
if (DEBUG_VOL)
Log.v(TAG, "getActiveStreamType: Forcing STREAM_MUSIC stream active");
return AudioSystem.STREAM_MUSIC;
} else {
if (DEBUG_VOL)
Log.v(TAG, "getActiveStreamType: Forcing STREAM_RING b/c default");
return AudioSystem.STREAM_RING;
}
} else if (isAfMusicActiveRecently(0)) {
if (DEBUG_VOL)
Log.v(TAG, "getActiveStreamType: Forcing STREAM_MUSIC stream active");
return AudioSystem.STREAM_MUSIC;
}
break;
case PLATFORM_TELEVISION:
if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {
// TV always defaults to STREAM_MUSIC
return AudioSystem.STREAM_MUSIC;
}
break;
default:
if (isInCommunication()) {
if (AudioSystem.getForceUse(AudioSystem.FOR_COMMUNICATION)
== AudioSystem.FORCE_BT_SCO) {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Forcing STREAM_BLUETOOTH_SCO");
return AudioSystem.STREAM_BLUETOOTH_SCO;
} else {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Forcing STREAM_VOICE_CALL");
return AudioSystem.STREAM_VOICE_CALL;
}
} else if (AudioSystem.isStreamActive(AudioSystem.STREAM_NOTIFICATION,
StreamOverride.sDelayMs) ||
AudioSystem.isStreamActive(AudioSystem.STREAM_RING,
StreamOverride.sDelayMs)) {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Forcing STREAM_NOTIFICATION");
return AudioSystem.STREAM_NOTIFICATION;
} else if (suggestedStreamType == AudioManager.USE_DEFAULT_STREAM_TYPE) {
if (isAfMusicActiveRecently(StreamOverride.sDelayMs)) {
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: forcing STREAM_MUSIC");
return AudioSystem.STREAM_MUSIC;
} else {
if (DEBUG_VOL) Log.v(TAG,
"getActiveStreamType: using STREAM_NOTIFICATION as default");
return AudioSystem.STREAM_NOTIFICATION;
}
}
break;
}
if (DEBUG_VOL) Log.v(TAG, "getActiveStreamType: Returning suggested type "
+ suggestedStreamType);
return suggestedStreamType;
}把isAfMusicActiveRecently(StreamOverride.sDelayMs) 改为： isAfMusicActiveRecently(0) 或一个小的值。Android声音焦点----从音乐回到Luncher调节音量显示的是Music的音量
原文地址：http://blog.csdn.net/deng0zhaotai/article/details/45058935
