Android 音量调节

最新推荐文章于 2025-03-29 11:13:45 发布

cuitianxiang

最新推荐文章于 2025-03-29 11:13:45 发布

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分类专栏： android 4.4音量调节与计算

本文链接：https://blog.youkuaiyun.com/cuitianxiang/article/details/42455363

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本文详细解析了Android系统中音量调节的过程，重点介绍了AudioService.java中的adjustStreamVolume函数，涉及音量指数调整、设备音量管理、蓝牙设备音量控制以及与铃声模式的交互。通过对函数的分析，揭示了音量调节如何影响AudioFlinger并改变应用的音量显示。

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音量调节在AudioService.java 的借口函数是 adjustStreamVolume 如下:

public void adjustStreamVolume(int streamType, int direction, int flags,
            String callingPackage) {
        if (mUseFixedVolume) {
            return;
        }
        if (DEBUG_VOL) Log.d(TAG, "adjustStreamVolume() stream="+streamType+", dir="+direction);

        ensureValidDirection(direction);
        ensureValidStreamType(streamType);

        // use stream type alias here so that streams with same alias have the same behavior,
        // including with regard to silent mode control (e.g the use of STREAM_RING below and in
        // checkForRingerModeChange() in place of STREAM_RING or STREAM_NOTIFICATION)
        int streamTypeAlias = mStreamVolumeAlias[streamType];
        VolumeStreamState streamState = mStreamStates[streamTypeAlias];

        final int device = getDeviceForStream(streamTypeAlias);

        int aliasIndex = streamState.getIndex(device);
        boolean adjustVolume = true;
        int step;

        // skip a2dp absolute volume control request when the device
        // is not an a2dp device
        if ((device & AudioSystem.DEVICE_OUT_ALL_A2DP) == 0 &&
            (flags & AudioManager.FLAG_BLUETOOTH_ABS_VOLUME) != 0) {
            return;
        }

        if (mAppOps.noteOp(STEAM_VOLUME_OPS[streamTypeAlias], Binder.getCallingUid(),
                callingPackage) != AppOpsManager.MODE_ALLOWED) {
            return;
        }

        // reset any pending volume command
        synchronized (mSafeMediaVolumeState) {
            mPendingVolumeCommand = null;
        }

        flags &= ~AudioManager.FLAG_FIXED_VOLUME;
        if ((streamTypeAlias == AudioSystem.STREAM_MUSIC) &&
               ((device & mFi

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