如何修改frameworks实现音量统一调节

修改音量最大值和默认音量

拦截音量键分发

在其他应用中添加广播接收者处理音量加减广播

打开主音量调节功能设置音量加减步长

测试

源码为MTK的MT8735平台源码，android 5

1 修改音量最大值和默认音量

源码位置：frameworks/base/media/java/android/media/AudioService.java 约266行

MAX_STREAM_VOLUME为最大值，DEFAULT_STREAM_VOLUME为默认值

为了统一调节音量，把默认音量和最大音量，所有STREAM都保持一致。

如果采用Master音量调节，就不需要设置了，因为Master音量调节最大都是100

/** @hide Maximum volume index values for audio streams */
/// M: Modify the max stream volume @{
private static final int[] MAX_STREAM_VOLUME = new int[] {
20,  // STREAM_VOICE_CALL
20,  // STREAM_SYSTEM
20,  // STREAM_RING
20,  // STREAM_MUSIC
20,  // STREAM_ALARM
20,  // STREAM_NOTIFICATION
20,  // STREAM_BLUETOOTH_SCO
20,  // STREAM_SYSTEM_ENFORCED
20,  // STREAM_DTMF
20,  // STREAM_TTS
};
/// @}

/**
* @hide Default volume index values for audio streams
* M: modify the default stream volume @{
*/
public static int[] DEFAULT_STREAM_VOLUME = new int[] {
9,  // STREAM_VOICE_CALL
9,  // STREAM_SYSTEM
9,  // STREAM_RING
9,  // STREAM_MUSIC
9,  // STREAM_ALARM
9,  // STREAM_NOTIFICATION
9,  // STREAM_BLUETOOTH_SCO
9,  // STREAM_SYSTEM_ENFORCED
9,  // STREAM_DTMF
9,  // STREAM_TTS
};
/** @ */

2 拦截音量键分发

源码位置：frameworks/base/policy/src/com/android/internel/policy/impl/PhoneWindowManager.java 约2607行

方法名：public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags)

作用：在分发之前拦截按键事件。是否分发给应用自己处理，根据返回值：return -1 不返回，自己处理了。return 0 返回给应用自己处理

拦截音量键

音量键码：KeyEvent.KEYCODE_VOLUME_DOWN KeyEvent.KEYCODE_VOLUME_UP

if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN || keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
// TODO: 这里添加你需要音量键按下后做什么事
return -1;
}

我们需要音量键按下后，发出按下广播。（来电铃声响起时，音量键起到静音作用，所以来电话的时候不拦截音量键，让系统处理）

Intent intent = new Intent();
intent.addFlags(Intent.FLAG_INCLUDE_STOPPED_PACKAGES);
if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN || keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
TelecomManager telecomManager = getTelecommService();
if (telecomManager == null || !(telecomManager.isRinging() || telecomManager.isInCall())) {
if (down) {
if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {
intent.setAction("xxx.ACTION_VOLUME_DOWN");
mContext.sendBroadcast(intent);
} else if (keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
intent.setAction("xxx.ACTION_VOLUME_UP");
mContext.sendBroadcast(intent);
}
return -1;
}
}
}

3 在其他应用中添加广播接收者处理音量加减广播

public class VolumeEventReceiver extends BroadcastReceiver {
Context mContext;
AudioManager manager;
int[] stream = {
AudioManager.STREAM_RING,
AudioManager.STREAM_ALARM,
AudioManager.STREAM_NOTIFICATION,
AudioManager.STREAM_DTMF,
AudioManager.STREAM_VOICE_CALL,
AudioManager.STREAM_SYSTEM,
AudioManager.STREAM_MUSIC,
};

@Override
public void onReceive(Context context, Intent intent) {
try {
mContext = context;
manager = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);

String action = intent.getAction();
if ("xxx.ACTION_VOLUME_DOWN".equals(action)) {
controlVolume(AudioManager.ADJUST_LOWER);

} else if ("xxx.ACTION_VOLUME_UP".equals(action)) {
controlVolume(AudioManager.ADJUST_RAISE);
}

} catch (Exception e) {
Log.i("VolumeEvent", "*** Exception: " + e.getMessage());
}
}

void controlVolume(int direction) {
for (int i = 0; i < stream.length - 1; i++) {
manager.adjustStreamVolume(stream[i], direction, 0);
}
// 显示媒体音量调节的图标，其他音量图标不显示
manager.adjustStreamVolume(AudioManager.STREAM_MUSIC, direction,
AudioManager.FLAG_SHOW_UI | AudioManager.FLAG_PLAY_SOUND);
}

}

注册广播：

<receiver android:name=".VolumeEventReceiver"
android:exported="false">
<intent-filter>
<action android:name="xxx.ACTION_VOLUME_DOWN" />
<action android:name="xxx.ACTION_VOLUME_UP" />
</intent-filter>
</receiver>

4 打开主音量调节功能，设置音量加减步长

源码位置：frameworks/base/core/res/res/values/config.xml 约71行

将config_useMasterVolume设置为true。

<!-- Flag indicating that the media framework should allow changing
master volume stream and nothing else . -->
<bool name="config_useMasterVolume">true</bool>

约86行，第二个item根据调试设置步长。默认是5， 这里改成1。根据测试，调节音量时，从最小到最大，需要按+键16下左右

<integer-array name="config_masterVolumeRamp">
<item>0</item>  <item>1</item>  <!-- default: always increase volume by 5% -->
</integer-array>

当用户调用adjustStreamVolume的时候，mUseMasterVolume是上面config_useMasterVolume的值。

public void adjustStreamVolume(int streamType, int direction, int flags) {
IAudioService service = getService();
Log.d(TAG, "adjustStreamVolume: StreamType = " + streamType + ", direction = " + direction);
try {
if (mUseMasterVolume) {
service.adjustMasterVolume(direction, flags, mContext.getOpPackageName());
} else {
service.adjustStreamVolume(streamType, direction, flags,
mContext.getOpPackageName());
}
} catch (RemoteException e) {
Log.e(TAG, "Dead object in adjustStreamVolume", e);
}
}

由Master调节音量，所有音量最大为100，发出音量调节广播为：

“android.media.MASTER_VOLUME_CHANGED_ACTION”

而普通的音量调节，最大音量根据AudioService.java中MAX_STREAM_VOLUME定义的，默认音量DEFAULT_STREAM_VOLUME

广播为：“android.media.VOLUME_CHANGED_ACTION”

5 测试

写一个测试程序测试