先上一張個人專案研發settings應用的一個功能，效果圖如下：

個人根據專案相關程式碼跟蹤到framework層時（framework層關鍵程式碼如下：）

@Override
    public int adjustVolumeLevel(int volumeType, int level) {
        if (null == mAudioManager) {
            return -1;
        }

        boolean bMcuMute = false;

        if (null == mSettingService) {
            mSettingService = SettingService.getInstance();
        }

        if
 
 (null != mSettingService) {
            try {
                bMcuMute = mSettingService.isMcuMute();
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

        switch (volumeType) {
        case VOLUME_TYPE_MUSIC:
        case VOLUME_TYPE_NVGIS:
            if
 
 (level >= 0 && masterMax() >= level) {
                if (bMcuMute && 0 != level) {
                    setSystemMute(false);
                }

                mAudioManager.setStreamVolume(AudioManager.STREAM_GIS, level, 0);
                mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, level, 0
 
);
                saveAudioTypeVolumeLevel(AudioManager.STREAM_GIS, level);
                saveAudioTypeVolumeLevel(AudioManager.STREAM_MUSIC, level);
            }
            break;
        case VOLUME_TYPE_BTHFP:
            if (level >= 0 && bthfpMax() >= level) {
                mAudioManager.setStreamVolume(AudioManager.STREAM_BLUETOOTH_SCO, level, 0);
                saveAudioTypeVolumeLevel(AudioManager.STREAM_BLUETOOTH_SCO, level);
            }
            break;
        case VOLUME_TYPE_BKCAR:
            if (level >= 0 && backcarMax() >= level) {
                mAudioManager.setStreamVolume(AudioManager.STREAM_BACKCAR, level, 0);
                saveAudioTypeVolumeLevel(AudioManager.STREAM_BACKCAR, level);
            }
            break;
        case VOLUME_TYPE_xRING:
            if (level >= 0 && ringMax() >= level) {
                mAudioManager.setStreamVolume(AudioManager.STREAM_RING, level, 0);
                saveAudioTypeVolumeLevel(AudioManager.STREAM_RING, level);
            }
            break;
        default:
            break;
        }

        return 0;
    }

發現Android實際上已經針對不同音源的不同音量設定提供了介面，其原始碼路徑為<個人使用的是Android4.2.2平臺程式碼>：path:\android4.2.2\frameworks\base\media\java\android\media\AudioService.java，部分關鍵程式碼如下：

/** @see AudioManager#setStreamVolume(int, int, int) */
    public void setStreamVolume(int streamType, int index, int flags) {
        ensureValidStreamType(streamType);
        VolumeStreamState streamState = mStreamStates[mStreamVolumeAlias[streamType]];

        final int device = getDeviceForStream(streamType);
        int oldIndex;
        boolean force = false;

        flags &= ~AudioManager.FLAG_FIXED_VOLUME;
        if ((mStreamVolumeAlias[streamType] == AudioSystem.STREAM_MUSIC) &&
                ((device & mFixedVolumeDevices) != 0)) {
            flags |= AudioManager.FLAG_FIXED_VOLUME;
            index = mStreamStates[streamType].getMaxIndex();
            oldIndex = index;
        } else {
            // get last audible index if stream is muted, current index otherwise
            oldIndex = streamState.getIndex(device,
                                            (streamState.muteCount() != 0) /* lastAudible */);

            index = rescaleIndex(index * 10, streamType, mStreamVolumeAlias[streamType]);

            if (!checkSafeMediaVolume(mStreamVolumeAlias[streamType], index, device)) {
                return;
            }

            if (mStreamVolumeAlias[streamType] == AudioSystem.STREAM_MUSIC) {
                force = true;
            }

            // setting volume on master stream type also controls silent mode
            if (((flags & AudioManager.FLAG_ALLOW_RINGER_MODES) != 0) ||
                    (mStreamVolumeAlias[streamType] == getMasterStreamType())) {
                int newRingerMode;
                if (index == 0) {
                    newRingerMode = mHasVibrator ? AudioManager.RINGER_MODE_VIBRATE
                                                  : AudioManager.RINGER_MODE_SILENT;
                    setStreamVolumeInt(mStreamVolumeAlias[streamType],
                                       index,
                                       device,
                                       force,
                                       true);
                } else {
                    newRingerMode = AudioManager.RINGER_MODE_NORMAL;
                    setRingerMode(newRingerMode);
                }

                //setRingerMode(newRingerMode);  移動到else中,正對Ring = 0避免全部靜音
            }

            setStreamVolumeInt(mStreamVolumeAlias[streamType], index, device, false, true);
            // get last audible index if stream is muted, current index otherwise
            index = mStreamStates[streamType].getIndex(device,
                                    (mStreamStates[streamType].muteCount() != 0) /* lastAudible */);
        }
        sendVolumeUpdate(streamType, oldIndex, index, flags);
    }

這邊實際上是AudioManager呼叫了AudioService的相關方法，而AudioService又呼叫了本地jni庫的方法。

上層使用方式：

我們直接通過context取get一個AudioManager管理者，然後通過設定不同音訊通道即可，程式碼如下：

mAudioManager.setStreamVolume(AudioManager.STREAM_GIS, level, 0);
                mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, level, 0);

mAudioManager.setStreamVolume(AudioManager.STREAM_BLUETOOTH_SCO, level, 0);

mAudioManager.setStreamVolume(AudioManager.STREAM_BACKCAR, level, 0);
mAudioManager.setStreamVolume(AudioManager.STREAM_RING, level, 0);