AudioService 和AudioManager 以及使用举例.

/**

 * The implementation of the volume manager service.

 * <p>

 * This implementation focuses on delivering a responsive UI. Most methods are

 * asynchronous to external calls. For example, the task of setting a volume

 * will update our internal state, but in a separate thread will set the system

 * volume and later persist to the database. Similarly, setting the ringer mode

 * will update the state and broadcast a change and in a separate thread later

 * persist the ringer mode.

 *

 * @hide
 */

frameworks/base/media/java/android/media/AudioService .java

public class AudioService extends IAudioService.Stub {

}

AudioService .java 提供了audio service 的服务实现, IAudioService.aidl 定义了服务的方法.

private static IAudioService sService;

/**
* @hide
*/
public AudioManager(Context context) {
mContext = context;
mMediaPlayers = new ArrayList<MediaPlayerInfo>(1);
mUseMasterVolume = mContext.getResources().getBoolean(
com.android.internal.R.bool.config_useMasterVolume);
mUseVolumeKeySounds = mContext.getResources().getBoolean(
com.android.internal.R.bool.config_useVolumeKeySounds);
mUseFixedVolume = mContext.getResources().getBoolean(
com.android.internal.R.bool.config_useFixedVolume);
sAudioPortEventHandler.init();
}

private static IAudioService getService()
{
if (sService != null) {
return sService;
}
IBinder b = ServiceManager.getService(Context.AUDIO_SERVICE);
sService = IAudioService.Stub.asInterface(b);
return sService;
}

IBinder b = ServiceManager.getService(Context.AUDIO_SERVICE);
sService = IAudioService.Stub.asInterface(b)

AudioManager 封装了AudioService的服务,并通过getservice 获取到AudioService的 Service 实例. 

实现了服务和服务的manager, java 应用层的使用方法 ,找到了个例子说明.

导入提供服务的java包

import android.media.AudioManager; 

定义私有对象. 

private AudioManager mAudioManager;

        获取服务并转换成AudioManger 类型.

       mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);

 获取原始音量.

        mOriginalMasterVol = mAudioManager.getMasterVolume();

        mShutterVol =  SystemProperties.getInt("persist.camera.snapshot.volume", -1);
        if (mShutterVol >= 0 && mShutterVol <= 100 )

            mAudioManager.setMasterVolume(mShutterVol,0);  调用服务提供的方法设置音量.  

这样就实现了audio的 Service manger 的调用流程.  当然这只是Service 的大概说明. 

总的框架掌握了. 细节慢慢分析吧.