Android音频相关（一）插入耳机后调节音量（安全音量）

一、安全音量提醒框的开启

二、修改安全音量提醒框显示

三、重启后还会显示安全音量提醒框

四、一些关于安全音量的初始值

一、安全音量提醒框的开启

安卓系统是有耳机音量保护机制的，对于一些出口欧盟的手机来说，这个提醒是必须存在的。当然安卓系统也是有这个功能的。我们下面就来简单介绍一下

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

 private void onConfigureSafeVolume(boolean force, String caller) {                     ///modify by xiangzaixiansheng for @{              ///这个主要是修改下面的布尔值为true；                boolean safeMediaVolumeEnabled =                        SystemProperties.getBoolean("audio.safemedia.force", true)                        || mContext.getResources().getBoolean(                                com.android.internal.R.bool.config_safe_media_volume_enabled);               ///}@               }

对于提醒的安全音量值来说

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

 8    true

二、修改安全音量提醒框显示

在安卓原生的逻辑中，达到安全音量后，如果再增加音量，安全音量提醒框会消失。这样其实不太符合欧盟国家的要求。所以简单修改成，用户必须点击确认，才能消失安全音量提醒框。

/frameworks/base/packages/SystemUI/src/com/android/systemui/volume/SafetyWarningDialog.java

 public boolean onKeyUp(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_VOLUME_UP && mNewVolumeUp                && (System.currentTimeMillis() - mShowTime) > KEY_CONFIRM_ALLOWED_AFTER) {            if (D.BUG) Log.d(TAG, "Confirmed warning via VOLUME_UP");            //modify by xiangzaixiansheng @{            //mAudioManager.disableSafeMediaVolume();            //dismiss();            ///}@        }        return super.onKeyUp(keyCode, event);    }

三、重启后还会显示安全音量提醒框

1: 可以在 AudioService.java 的构造方法中设个变量, 比如 bool bIsFirstBoot = true;

2: 然后在 checkSafeMediaVolume 方法中, 判断此变量, 如下:

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

private boolean checkSafeMediaVolume(int streamType, int index, int device) {synchronized (mSafeMediaVolumeState) {//add beginif(bIsFirstBoot){mSafeMediaVolumeState = SAFE_MEDIA_VOLUME_ACTIVE;bIsFirstBoot = false;}//add endsif ((mSafeMediaVolumeState == SAFE_MEDIA_VOLUME_ACTIVE) &&(mStreamVolumeAlias[streamType] == AudioSystem.STREAM_MUSIC) &&((device & mSafeMediaVolumeDevices) != 0) &&(index > mSafeMediaVolumeIndex)) {return false;}return true;}}

四、一些关于安全音量的初始值

public class AudioService extends IAudioService.Stub {    // mSafeMediaVolumeState 当前媒体音量是否被限制的状态标识.    // 设备启动时为 SAFE_MEDIA_VOLUME_NOT_CONFIGURED.     // 根据国家不同或是 SAFE_MEDIA_VOLUME_ACTIVE 或是 SAFE_MEDIA_VOLUME_DISABLED.    // 当用户确认过后会调用 disableSafeMediaVolume() 设为 SAFE_MEDIA_VOLUME_INACTIVE.    private static final int SAFE_MEDIA_VOLUME_NOT_CONFIGURED = 0;    private static final int SAFE_MEDIA_VOLUME_DISABLED = 1;    private static final int SAFE_MEDIA_VOLUME_INACTIVE = 2;    private static final int SAFE_MEDIA_VOLUME_ACTIVE = 3;    private Integer mSafeMediaVolumeState;    // Mobile country code，这里主要用来区分国家    private int mMcc = 0;    // 安全音量值    private int mSafeMediaVolumeIndex;    // mSafeMediaVolumeDevices 强制开启SafeVolume的输出设备（耳机）    private final int mSafeMediaVolumeDevices = AudioSystem.DEVICE_OUT_WIRED_HEADSET |                                                AudioSystem.DEVICE_OUT_WIRED_HEADPHONE;    // mMusicActiveMs 在禁用SafeVolume下的使用耳机的累计时长.    // 当累计达到 UNSAFE_VOLUME_MUSIC_ACTIVE_MS_MAX 时会自动开启SafeVolume    private int mMusicActiveMs;    private static final int UNSAFE_VOLUME_MUSIC_ACTIVE_MS_MAX = (20 * 3600 * 1000); // 20 hours    private static final int MUSIC_ACTIVE_POLL_PERIOD_MS = 60000;  // 1 minute polling interval    private static final int SAFE_VOLUME_CONFIGURE_TIMEOUT_MS = 30000;  // 30s after boot completed    ...

private void onConfigureSafeVolume(boolean force, String caller) {    synchronized (mSafeMediaVolumeState) {        int mcc = mContext.getResources().getConfiguration().mcc;        if ((mMcc != mcc) || ((mMcc == 0) && force)) {            // 从 values 中获取具体的安全音量阈值            mSafeMediaVolumeIndex =  mContext.getResources().getInteger(com.android.internal.R.integer.config_safe_media_volume_index) * 10;            boolean safeMediaVolumeEnabled =  SystemProperties.getBoolean("audio.safemedia.force", false) || mContext.getResources().getBoolean(com.android.internal.R.bool.config_safe_media_volume_enabled);            boolean safeMediaVolumeBypass =                     SystemProperties.getBoolean("audio.safemedia.bypass", false);            // persitedSate 只会是 "disabled" 或者 "active"，这个变量值作用于下次启动且不能是 "inactive"            int persistedState;            if (safeMediaVolumeEnabled && !safeMediaVolumeBypass) {                persistedState = SAFE_MEDIA_VOLUME_ACTIVE;                // 有可能在这个方法被调用之前用户已经设为"inactive"了.                if (mSafeMediaVolumeState != SAFE_MEDIA_VOLUME_INACTIVE) {                    if (mMusicActiveMs == 0) {                        mSafeMediaVolumeState = SAFE_MEDIA_VOLUME_ACTIVE;                        // 降低音量到安全阈值                        enforceSafeMediaVolume(caller);                    } else {                        // 用户已经过确认                        mSafeMediaVolumeState = SAFE_MEDIA_VOLUME_INACTIVE;                    }                }            } else {                persistedState = SAFE_MEDIA_VOLUME_DISABLED;                mSafeMediaVolumeState = SAFE_MEDIA_VOLUME_DISABLED;            }            mMcc = mcc;            // 发送保存 persistedState 的消息            sendMsg(mAudioHandler,                    MSG_PERSIST_SAFE_VOLUME_STATE,                    SENDMSG_QUEUE,                    persistedState,                    0,                    null,                    0);        }    }}

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