Android4.0 音量调节

1. 音量调节流程

AudioManager.java->

    AudioService.java(调节音量)->

        AudioSystem.java->

           android_media_AudioSystem.cpp->

              AudioSystem.cpp->

                  AudioPolicyService.cpp->

                     Audio HAL

2. 相关数据结构

1) VolumeStreamState: 保存音量值

2) Default和MAX值

#### AudioManager.java

    /**  @hide Default volume index values for audio streams */
    public static final int[] DEFAULT_STREAM_VOLUME = new int[] {
        4,  // STREAM_VOICE_CALL
        7,  // STREAM_SYSTEM
        5,  // STREAM_RING
        11, // STREAM_MUSIC
        6,  // STREAM_ALARM
        5,  // STREAM_NOTIFICATION
        7,  // STREAM_BLUETOOTH_SCO
        7,  // STREAM_SYSTEM_ENFORCED
        11, // STREAM_DTMF
        11  // STREAM_TTS
    };

 

#### AudioService.java

   /** @hide Maximum volume index values for audio streams */
    private int[] MAX_STREAM_VOLUME = new int[] {
        5,  // STREAM_VOICE_CALL
        7,  // STREAM_SYSTEM
        7,  // STREAM_RING
        15, // STREAM_MUSIC
        7,  // STREAM_ALARM
        7,  // STREAM_NOTIFICATION
        15, // STREAM_BLUETOOTH_SCO
        7,  // STREAM_SYSTEM_ENFORCED
        15, // STREAM_DTMF
        15  // STREAM_TTS
    };

 

3) 流名字

Settings.java

        /**
         * The mapping of stream type (integer) to its setting.
         */
        public static final String[] VOLUME_SETTINGS = {
            VOLUME_VOICE, VOLUME_SYSTEM, VOLUME_RING, VOLUME_MUSIC,
            VOLUME_ALARM, VOLUME_NOTIFICATION, VOLUME_BLUETOOTH_SCO
        };

        public static final String MODE_RINGER = "mode_ringer";
        public static final String MODE_RINGER_STREAMS_AFFECTED = "mode_ringer_streams_affected";
        public static final String MUTE_STREAMS_AFFECTED = "mute_streams_affected";
        public static final String VIBRATE_ON = "vibrate_on";
        public static final String VOLUME_RING = "volume_ring";
        public static final String VOLUME_SYSTEM = "volume_system";
        public static final String VOLUME_VOICE = "volume_voice";
        /**
         * Music/media/gaming volume. This is used internally, changing this
         * value will not change the volume. See AudioManager.
         */
        public static final String VOLUME_MUSIC = "volume_music";
        public static final String VOLUME_ALARM = "volume_alarm";
        public static final String VOLUME_NOTIFICATION = "volume_notification";
        public static final String VOLUME_BLUETOOTH_SCO = "volume_bluetooth_sco";