Android 音量调节（二）-Android10 音量调节源码实现流程

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已于 2024-03-25 16:29:50 修改

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分类专栏： android framework 音频文章标签： android

于 2024-03-19 18:36:50 首次发布

本文链接：https://blog.youkuaiyun.com/nysin/article/details/136842962

版权

本文围绕Android 10系统，介绍了系统调节音量的实现和默认音量修改。详细阐述按实体音量键修改音量的流程，进入AudioService后，分析了adjustSuggestedStreamVolume和adjustStreamVolume等方法，涉及音频流类型判断、权限检查、音量调整等逻辑，最终完成framework层音量修改。

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上一篇文章描述了在app开发中怎么调节系统不同音频流的音量大小。这次我们看下在android10中系统调节音量的实现和系统默认音量的修改。（本次源码以Android10为主梳理系统音量修改的实现）

一按实体音量键修改音量

// frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java
//以下按键事件中
if (keyCode == KeyEvent.KEYCODE_VOLUME_UP
                || keyCode == KeyEvent.KEYCODE_VOLUME_DOWN
                || keyCode == KeyEvent.KEYCODE_VOLUME_MUTE) {
            if (mUseTvRouting || mHandleVolumeKeysInWM) {
                // On TVs or when the configuration is enabled, volume keys never
                // go to the foreground app.
                dispatchDirectAudioEvent(event);
                return -1;
            }

 private void dispatchDirectAudioEvent(KeyEvent event) {
        // When System Audio Mode is off, volume keys received by AVR can be either consumed by AVR
        // or forwarded to the TV. It's up to Amplifier manufacturer’s implementation.
        HdmiControlManager hdmiControlManager = getHdmiControlManager();
        if (null != hdmiControlManager
                && !hdmiControlManager.getSystemAudioMode()
                && shouldCecAudioDeviceForwardVolumeKeysSystemAudioModeOff()) {
            HdmiAudioSystemClient audioSystemClient = hdmiControlManager.getAudioSystemClient();
            if (audioSystemClient != null) {
                audioSystemClient.sendKeyEvent(
                        event.getKeyCode(), event.getAction() == KeyEvent.ACTION_DOWN);
                return;
            }
        }
        if (event.getAction() != KeyEvent.ACTION_DOWN) {
            return;
        }
        int keyCode = event.getKeyCode();
        int flags = AudioManager.FLAG_SHOW_UI | AudioManager.FLAG_PLAY_SOUND
                | AudioManager.FLAG_FROM_KEY;
        String pkgName = mContext.getOpPackageName();

        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_UP:
                try {
                    getAudioService().adjustSuggestedStreamVolume(AudioManager.ADJUST_RAISE,
                            AudioManager.USE_DEFAULT_STREAM_TYPE, flags, pkgName, TAG);
                } catch (Exception e) {
                    Log.e(TAG, "Error dispatching volume up in dispatchTvAudioEvent.", e);
                }
                break;
            case KeyEvent.KEYCODE_VOLUME_DOWN:
                try {
                    getAudioService().adjustSuggestedStreamVolume(AudioManager.ADJUST_LOWER,
                            AudioManager.USE_DEFAULT_STREAM_TYPE, flags, pkgName, TAG);
                } catch (Exception e) {
                    Log.e(TAG, "Error dispatching volume down in dispatchTvAudioEvent.", e);
                }
                break;
            case KeyEvent.KEYCODE_VOLUME_MUTE:
                try {
                    if (event.getRepeatCount() == 0) {
                        getAudioService().adjustSuggestedStreamVolume(
                                AudioManager.ADJUST_TOGGLE_MUTE,
                                AudioManager.USE_DEFAULT_STREAM_TYPE, flags, pkgName, TAG);
                    }
                } catch (Exception e) {
                    Log.e(TAG, "Error dispatching mute in dispatchTvAudioEvent.", e);
                }
                break;
        }
    }

以上方法dispatchDirectAudioEvent（）方法体中，根据不同的按键事件处理音量调节（增大、减小、静音）
说明：

按键类型	Audio Service操作类型	含义
KEYCODE_VOLUME_UP	AudioManager.ADJUST_RAISE	音量减
KEYCODE_VOLUME_DOWN	AudioManager.ADJUST_LOWER	音量加
KEYCODE_VOLUME_MUTE	AudioManager.ADJUST_TOGGLE_MUTE	改变静音状态

二进入AudioService

getAudioService()获取AudioService实例，
接下来就到了AudioService中的adjustSuggestedStreamVolume方法里面了:

public void adjustSuggestedStreamVolume(int direction, int suggestedStreamType, int flags,
            String callingPackage, String caller) {
        final IAudioPolicyCallback extVolCtlr;
        synchronized (mExtVolumeControllerLock) {
            extVolCtlr = mExtVolumeController;
        }
        if (extVolCtlr != null) {
            sendMsg(mAudioHandler, MSG_NOTIFY_VOL_EVENT, SENDMSG_QUEUE,
                    direction, 0 /*ignored*/,
                    extVolCtlr, 0 /*delay*/);
        } else {
            adjustSuggestedStreamVolume(direction, suggestedStreamType, flags, callingPackage,
                    caller, Binder.getCallingUid());
        }
    }

以上代码中，extVolCtrlr是外部设备（如蓝牙设备，有线耳机等可操作音量的设备）实例，
1）若extVolCtrlr！=null，执行
onNotifyVolumeEvent((IAudioPolicyCallback) msg.obj, msg.arg1);
然后外部设备发送信号到系统。系统再调用adjustSuggestedStreamVolume方法实现音量调节（该部分未找到源码麻烦指正）
2）若extVolCtrlr == null 执行

private void adjustSuggestedStreamVolume(int direction, int suggestedStreamType, int flags, String callingPackage, String caller, int uid) {
       //...省略部分代码
        final int streamType;
        synchronized (mForceControlStreamLock) {
            // Request lock in case mVolumeControlStream is changed by other thread.
            if (mUserSelectedVolumeControlStream) { // implies mVolumeControlStream != -1
                streamType = mVolumeControlStream;
            } else {
                final int maybeActiveStreamType = getActiveStreamType(suggestedStreamType);
                final boolean activeForReal;
                if (maybeActiveStreamType =