android Camera 錄像時旋轉角度

錄像保存時，旋轉角度要與所拍錄像時的角度保持一致，否則，看起來就會出現角度不度，巔倒等問題。

一般在開始錄像之前會先去初始化錄像

initializeRecorder 中會去讀取當前的錄像或拍照的旋轉角度，並跟據當前的角度來選擇一個角度寫到所拍

照片或者視頻的 exif 信息中去。

// See android.hardware.Camera.Parameters.setRotation for  
        // documentation.  
        // Note that mOrientation here is the device orientation, which is the opposite of  
        // what activity.getWindowManager().getDefaultDisplay().getRotation() would return,  
        // which is the orientation the graphics need to rotate in order to render correctly.  
        int rotation = 0;  
        if (mOrientation != OrientationEventListener.ORIENTATION_UNKNOWN) {  
            CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];  
            if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {  
                rotation = (info.orientation - mOrientation + 360) % 360;  
            } else {  // back-facing camera  
                rotation = (info.orientation + mOrientation) % 360;  
            }  
        } else {  
            //Get the right original orientation  
            CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];  
            rotation = info.orientation;  
        }  
//        mMediaRecorder.setOrientationHint(rotation);  
  
        if (mCameraId == CameraInfo.CAMERA_FACING_FRONT) {  
            if (rotation == 270 || rotation == 90 || rotation == 180) {  
                mMediaRecorder.setOrientationHint(180);  
            } else {  
                mMediaRecorder.setOrientationHint(0);  
            }  
        } else {  
            if (rotation == 180){  
                mMediaRecorder.setOrientationHint(180);  
            }else{  
                mMediaRecorder.setOrientationHint(0);  
            }  
        }