JB4.2:添加一个SwithButton控制ShutterSound

在Andoird JB 4.2中，Camera的代码有非常大的变动，不管是frameworks，还是APP。逻辑更加严谨，google里的程序员真的很喜欢用设计模式，到处都可以看到设计模式的影子，刚刚拿到JB4.2源码的时候，我被绕晕了，一方面是代码变化太大，另一个最主要的因素还是自己功力不够。

现在，我们讨论一下如何在JB 4.2的Camera中实现一个功能：添加一个开关来控制拍照声音。

在4.2中实现应该说是更加简单了，因为系统在frameworks已经提供了一个方法：enableShutterSound(boolean enabled)，其实我们可以在上层直接调用该方法来控制shutterSound，但是实践证明，它只能控制拍照的声音，而录制的声音会失效。

我们先跟踪一下这个方法，enableShutterSound(boolean enabled)方法在frameworks/base/core/java/android/hardware/Camera.java中，

public final boolean enableShutterSound(boolean enabled) {
...
    return _enableShutterSound(enabled);
}

private native final boolean _enableShutterSound(boolean enabled);

在这里，它调用了一个native方法_enableShutterSound(boolean enabled)，查看JNI目录，在

frameworks/base/core/jni/android_hardware_Camera.cpp文件中，如下代码：

static JNINativeMethod camMethods[] = {
    ...
    {"_enableShutterSound","(Z)Z",(void *)anroid_hardware_Camera_enableShutterSound},
    ...
}

然后我们分析

android_hardware_Camera_enableShutterSound()

如下：

static jboolean android_hardware_Camera_enableShutterSound(JNIEnv *env, jobject thiz, jboolean enabled) {
     ...
     status_t rc = camera->sendCommand(CAMERA_CMD_ENABLE_SHUTTER_SOUND, value, 0);
     ...
}

然后转到frameworks/av/services/camera/libcameraservice/CameraClient.cpp。从4.1开始，Camera被更加重视了，将av放到base同等级别的目录下，呵呵。

status_t CameraClient::sendCommand(int32_t cmd, int32_t arg1, int32_t arg2) {
    ...
    }else if(cmd == CAMERA_CMD_ENABLE_SHUTTER_SOUND) {
        switch(arg1) {
            case 0:
                return enableShutterSound(false);
            case 1:
                return enableShutterSound(true);
            default:
                return BAD_VALUE;
        }
        return OK;
    }
    ...
}

跟踪enableShutterSound方法，

status_t CameraClient::enableShutterSound(bool enable) {
    ...

    if (enable){
        mPlayShutterSound = true;
        return OK;
    }
    ...
    mPlayShutterSound = false;
    return false;
}

在snapshot taken callback，即

void CameraCilent::handleShutter(void) {
    if(mPlayShutterSound) {
         mCameraService->playSound(CameraService::SOUND_SHUTTER);
    }
    ...
}

 而在，录制视频的动作中，

status_t CameraCilent::startRecordingMode(){
    ...
    mCameraService->playSound(CameraService::SOUND_RECORDING);
    ...
}

void CameraCilent::stopRecording(){
    ...
    mCameraService->playSound(CameraService::SOUND_RECORDING);
    ...
}

因此，framework/base/core/java/android/hardware/Camera中的enableShutterSound对Recording没有作用，因此我们只需加入与拍照时的同等逻辑，即：

status_t CameraCilent::startRecordingMode(){
    ...
    if (mPlayShutterSound) {
        mCameraService->playSound(CameraService::SOUND_RECORDING);
    }
    ...
}

void CameraCilent::stopRecording(){
    ...
    if (mPlayShutterSound) {
        mCameraService->playSound(CameraService::SOUND_RECORDING);
    }
    ...
}

这样我们就可以直接在上层调用android.hardware.Camera中的enableShutterSound来控制拍照和录制模式的shutter sound.

下面实现app层的逻辑，正如我前面所说的那样，4.2的改动很大，不过改动起来还是很方便的。

在UI方面，因为要在CameraSettings中添加一个开关，则需要做如下操作：

packages/apps/Camera/src/com/android/camera/SettingsChecker.java

...
public static final int ROW_SETTING_SHUTTER_SOUND = 51;
...

public static final int[] SETTING_GROUP_COMMON_FOR_TAB_MY_SETTING = new int[]{
...
   ROW_SETTING_SHUTTER_SOUND;
...
}

public static final int[] SETTING_GROUP_COMMON_FOR_TAB = new int[]{
...
   ROW_SETTING_SHUTTER_SOUND;
...
}

public static final int[] SETTING_GROUP_CAMERA_FOR_PARAMETERS = new int[]{
...
   ROW_SETTING_SHUTTER_SOUND;
...
}

public static final int[] SETTING_GROUP_VIDEO_FOR_PARAMETERS = new int[]{
...
   ROW_SETTING_SHUTTER_SOUND;
...
}

public static final int[] SETTING_GROUP_ALL_IN_SETTING = new int[]{
...
   ROW_SETTING_SHUTTER_SOUND;
...
}

static {
...
MATRIX_MODE_STATE[ROW_SETTING_SHUTTER_SOUND] = new int[]{STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO,STATE_EO};
...

RESET_STATE_VALUE[ROW_SETTING_SHUTTER_SOUND] = new String[]{"on"};
...

KEYS_FOR_SETTING[ROW_SETTING_SHUTTER_SOUND] = CameraSettings.KEY_SOUND;
...

MATRIX_SETTING_VISIBLE[CAMERA_BACK_ID][ROW_SETTING_SHUTTER_SOUND] = true;
...

MATRIX_SETTING_VISIBLE[CAMERA_FRONT_ID][ROW_SETTING_SHUTTER_SOUND] = true;
...

DEFAULT_VALUE_FOR_SETTING_ID[ROW_SETTING_SHUTTER_SOUND] = R.string.pref_camera_shuttersound_default;
...

}


private static String getParameterValue(Parameters parameters, int row) {
...
   case ROW_SETTING_SHUTTER_SOUND:
        throw new CameraSettingsException("Cannot get sound from parameters"); 
...

}  


private static boolean setParameterValue(Context context, Parameters parameters, int row, String Value) {
    ...
    case ROW_SETTING_SHUTTER_SOUND:
        updateShutterSound(context);
        break;
    ...
}


private static boolean isParamenterSupportedValue(Paramenters parameters, int row, String value) {
   ...
    case ROW_SETTING_SHUTTER_SOUND:
        support = true;
        break;
   ...
}

private static void updateShutterSound(Context context) {
    Camera camera = (Camera) context;
    camera.updateShutterSound();
}

packages/apps/Camera/src/com/android/camera/Camera.java

public static final int MSG_SHUTTER_SOUND_KEY = 24;

...

public void updateShutterSound() {
    mMainHandler.sendEmptyMessage(MSG_SHUTTER_SOUND_KEY);
}

...

public Handler mMainHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        ...
            case MSG_SHUTTER_SOUND_KEY:
                if ("on".equals(mSettingChecker.getStringCurrentValue(SettingChecker.ROW_SETTING_SHUTTER_SOUND))) {
                 mCameraActor.enableShutterSound(true);
             } else {
                 mCameraActor.enableShutterSound(false);
             }
        ...
    }

}

public void enableShutterSound(boolean enable) {
    mCameraDevice.enableShutterSound(enable);
}

packages/apps/Camera/src/com/android/camera/CameraManager.java

private static final int SET_SHUTTER_SOUND = 118;

public void enableShutterSound(boolean enable) {
    mSig.close();
    mCameraHandler.obtainMessage(SET_SHUTTER_SOUND,enable).sendToTarget();
    mSig.block();
}

private class CameraHandler extends Handler {
    ...
    @Override
    public void handleMessage(final Message msg) {
    ...
        case SET_SHUTTER_SOUND:
            mCamera.enableShutterSound((Boolean)msg.obj);
            break;
    ...
  
    }
    ...
}

packages/apps/Camera/src/com/mediatek/camera/ICamera.java

public interface ICamera {
    ...
    public void enableShutterSound(boolean enable);
    ...
}

packages/apps/Camera/src/com/mediatek/camera/AndroidCamera.java

...
import android.hardware.Camera;
...

public class AndroidCamera implements ICamera {
    ...
    protect Camera mCamera;
    ...
    public void enableShutterSound(boolean enable) {
        mCamera.enableShutterSound(enable);
    }
    ...
}

packages/apps/Camera/src/com/android/camera/actor/CameraActor.java

public void enableShutterSound(boolean enable) {
    mContext.enableShutterSound(enable);
}

从上面代码可以看出，AndroidCamera.java中的enableShutterSound方法调用了framework层android.hardware.Camera.enableShutterSound；而在Camera中，

case MSG_SHUTTER_SOUND_KEY:
                if ("on".equals(mSettingChecker.getStringCurrentValue(SettingChecker.ROW_SETTING_SHUTTER_SOUND))) {
                 mCameraActor.enableShutterSound(true);
             } else {
                 mCameraActor.enableShutterSound(false);
             }

在这里，只需简单的调用mCameraActor.enableShutterSound即可，而其他的Actor都是继承自CameraActor，也就是说，我们只需加上上述代码，其他各种模式的shutter sound 我们都可以控制了。其可扩展性确实挺高的，但是容易让人绕晕。