Android 6.0系统音量相关小知识点

系统默认的音量值

frameworks/base/media/java/android/media/AudioSystem.java

public static int[] DEFAULT_STREAM_VOLUME = new int[] {    4,  // STREAM_VOICE_CALL    15, // STREAM_SYSTEM    8,  // STREAM_RING    8,  // STREAM_MUSIC    8,  // STREAM_ALARM    8,  // STREAM_NOTIFICATION    7,  // STREAM_BLUETOOTH_SCO    15, // STREAM_SYSTEM_ENFORCED    11, // STREAM_DTMF    11  // STREAM_TTS};//获取输出设备和输入设备public static String getOutputDeviceName(int device) {    ...}public static String getInputDeviceName(int device) {    ...}

系统安全音量值的设置

frameworks/base/core/res/res/values/config.xml

<!-- 20170220 micheal modify 10 to 13 for home care app --><integer name="config_safe_media_volume_index">13</integer><!-- Whether safe headphone volume is enabled or not (country specific). --><bool name="config_safe_media_volume_enabled">true</bool>

系统音量的最大值和最小值

frameworks/base/services/core/java/com/android/server/audio/AudioService.java

/** Maximum volume index values for audio streams *//// M: Modify the max stream volume @{private static int[] MAX_STREAM_VOLUME = new int[] {    7,  // STREAM_VOICE_CALL    15,  // STREAM_SYSTEM    15,  // STREAM_RING    15, // STREAM_MUSIC    15,  // STREAM_ALARM    15,  // STREAM_NOTIFICATION    15, // STREAM_BLUETOOTH_SCO    15,  // STREAM_SYSTEM_ENFORCED    15, // STREAM_DTMF    15  // STREAM_TTS};/** Minimum volume index values for audio streams */private static int[] MIN_STREAM_VOLUME = new int[] {    1,  // STREAM_VOICE_CALL    0,  // STREAM_SYSTEM    0,  // STREAM_RING    0,  // STREAM_MUSIC    0,  // STREAM_ALARM    0,  // STREAM_NOTIFICATION    1,  // STREAM_BLUETOOTH_SCO    0,  // STREAM_SYSTEM_ENFORCED    0,  // STREAM_DTMF    0   // STREAM_TTS};

adb查看系统默认的配置users后面的0表示用户id，不同的用户对应不同的id

/data/system/users/0

参考文章

Android java层音频相关的分析与理解（一）基本框架
Android java层音频相关的分析与理解（二）音量控制相关
Android java层音频相关的分析与理解（三）调用相关
Android java层音频相关的分析与理解（四）音频外设相关
简单聊一下Android音频通路的切换

一点小小的经验： Android 上的「安全音量」
一点小小的经验： Android 上的「安全音量」