在之前的一些android版本中，修改默認音量是修改：

path：frameworks\base\media\java\android\media\AudioService.java

/// M: modify the default stream volume @{public static int[] DEFAULT_STREAM_VOLUME = new int[] {4, // STREAM_VOICE_CALL8, // STREAM_SYSTEM8, // STREAM_RING8, // STREAM_MUSIC8, // STREAM_ALARM8, // STREAM_NOTIFICATION8, // STREAM_BLUETOOTH_SCO8, // STREAM_SYSTEM_ENFORCED8, // STREAM_DTMF8, // STREAM_TTS8 // STREAM_ACCESSIBILITY};/// @}

當然此文件中也定義了Volume的最大值和最小值：

/** Maximum volume index values for audio streams *//// M: Modify the max stream volume @{protected static int[] MAX_STREAM_VOLUME = new int[] {7, // STREAM_VOICE_CALL15, // STREAM_SYSTEM15, // STREAM_RING15, // STREAM_MUSIC15, // STREAM_ALARM15, // STREAM_NOTIFICATION15, // STREAM_BLUETOOTH_SCO15, // STREAM_SYSTEM_ENFORCED15, // STREAM_DTMF15, // STREAM_TTS15 // STREAM_ACCESSIBILITY};/** Minimum volume index values for audio streams */protected static int[] MIN_STREAM_VOLUME = new int[] {1, // STREAM_VOICE_CALL0, // STREAM_SYSTEM0, // STREAM_RING0, // STREAM_MUSIC1, // STREAM_ALARM0, // STREAM_NOTIFICATION0, // STREAM_BLUETOOTH_SCO0, // STREAM_SYSTEM_ENFORCED0, // STREAM_DTMF0, // STREAM_TTS1 // STREAM_ACCESSIBILITY};

OK? 回歸主題，在android Q版本中DEFAULT_STREAM_VOLUME數組的定義是在AudioSystem.java文件中，但是修改這個數組中的值發現還是無法正確處理為自己想要的默認值。

發現初始化默認值是在AudioService.java的AudioService()方法中：

int maxCallVolume = SystemProperties.getInt("ro.config.vc_call_vol_steps", -1);if (maxCallVolume != -1) {MAX_STREAM_VOLUME[AudioSystem.STREAM_VOICE_CALL] = maxCallVolume;}int defaultCallVolume = SystemProperties.getInt("ro.config.vc_call_vol_default", -1);if (defaultCallVolume != -1 &&defaultCallVolume <= MAX_STREAM_VOLUME[AudioSystem.STREAM_VOICE_CALL] &&defaultCallVolume >= MIN_STREAM_VOLUME[AudioSystem.STREAM_VOICE_CALL]) {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_VOICE_CALL] = defaultCallVolume;} else {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_VOICE_CALL] =(maxCallVolume * 3) / 4;}int maxMusicVolume = SystemProperties.getInt("ro.config.media_vol_steps", -1);if (maxMusicVolume != -1) {MAX_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] = maxMusicVolume;}int defaultMusicVolume = SystemProperties.getInt("ro.config.media_vol_default", -1);if (defaultMusicVolume != -1 &&defaultMusicVolume <= MAX_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] &&defaultMusicVolume >= MIN_STREAM_VOLUME[AudioSystem.STREAM_MUSIC]) {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] = defaultMusicVolume;} else {if (isPlatformTelevision()) {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] =MAX_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] / 4;} else {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] =MAX_STREAM_VOLUME[AudioSystem.STREAM_MUSIC] / 3;}}int maxAlarmVolume = SystemProperties.getInt("ro.config.alarm_vol_steps", -1);if (maxAlarmVolume != -1) {MAX_STREAM_VOLUME[AudioSystem.STREAM_ALARM] = maxAlarmVolume;}int defaultAlarmVolume = SystemProperties.getInt("ro.config.alarm_vol_default", -1);if (defaultAlarmVolume != -1 &&defaultAlarmVolume <= MAX_STREAM_VOLUME[AudioSystem.STREAM_ALARM]) {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_ALARM] = defaultAlarmVolume;} else {// Default is 6 out of 7 (default maximum), so scale accordingly.AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_ALARM] =6 * MAX_STREAM_VOLUME[AudioSystem.STREAM_ALARM] / 7;}int maxSystemVolume = SystemProperties.getInt("ro.config.system_vol_steps", -1);if (maxSystemVolume != -1) {MAX_STREAM_VOLUME[AudioSystem.STREAM_SYSTEM] = maxSystemVolume;}int defaultSystemVolume = SystemProperties.getInt("ro.config.system_vol_default", -1);if (defaultSystemVolume != -1 &&defaultSystemVolume <= MAX_STREAM_VOLUME[AudioSystem.STREAM_SYSTEM]) {AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_SYSTEM] = defaultSystemVolume;} else {// Default is to use maximum.AudioSystem.DEFAULT_STREAM_VOLUME[AudioSystem.STREAM_SYSTEM] =MAX_STREAM_VOLUME[AudioSystem.STREAM_SYSTEM];}

發現這些初始化的值都是由一些ro.config.屬性控制的，所以要修改默認音量大小，可以直接客制化ro.config.這些屬性值就OK。

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