private void switchCameraOnCameraThread() {
   checkIsOnCameraThread();
   Logging.d(TAG, "switchCameraOnCameraThread");
   stopCaptureOnCameraThread();
   synchronized (cameraIdLock) {
     id = (id + 1) % Camera.getNumberOfCameras();
   }
   dropNextFrame = true;
   startCaptureOnCameraThread(
       requestedWidth, requestedHeight, requestedFramerate, frameObserver, applicationContext);
   Logging.d(TAG, "switchCameraOnCameraThread done");
 }
  private void startCaptureOnCameraThread(
      final int width,
      final int height,
      final int framerate,
      final CapturerObserver frameObserver,
      final Context applicationContext) {
    Throwable error = null;
    checkIsOnCameraThread();
    if (camera != null) {
      throw new RuntimeException("Camera has already been started.");
    }
    this.applicationContext = applicationContext;
    this.frameObserver = frameObserver;
    this.firstFrameReported = false;

    try {
      try {
        synchronized (cameraIdLock) {
          Logging.d(TAG, "Opening camera " + id);
          if (eventsHandler != null) {
            eventsHandler.onCameraOpening(id);
          }
          camera = Camera.open(id);
          info = new Camera.CameraInfo();
          Camera.getCameraInfo(id, info);
        }
      } catch (RuntimeException e) {
        openCameraAttempts++;
        if (openCameraAttempts < MAX_OPEN_CAMERA_ATTEMPTS) {
          Logging.e(TAG, "Camera.open failed, retrying", e);
          openCameraOnCodecThreadRunner =
              new Runnable() {
                @Override
                public void run() {
                  startCaptureOnCameraThread(
                      width, height, framerate, frameObserver, applicationContext);
                }
              };
          cameraThreadHandler.postDelayed(openCameraOnCodecThreadRunner, OPEN_CAMERA_DELAY_MS);
          return;
        }
        openCameraAttempts = 0;
        throw e;
      }

      try {
        camera.setPreviewTexture(surfaceHelper.getSurfaceTexture());
      } catch (IOException e) {
        Logging.e(TAG, "setPreviewTexture failed", error);
        throw new RuntimeException(e);
      }

      Logging.d(
          TAG,
          "Camera orientation: "
              + info.orientation
              + " .Device orientation: "
              + getDeviceOrientation());
      camera.setErrorCallback(cameraErrorCallback);
      startPreviewOnCameraThread(width, height, framerate);
      frameObserver.onCapturerStarted(true);

      // Start camera observer.
      cameraThreadHandler.postDelayed(cameraObserver, CAMERA_OBSERVER_PERIOD_MS);
      return;
    } catch (RuntimeException e) {
      error = e;
    }
    Logging.e(TAG, "startCapture failed", error);
    stopCaptureOnCameraThread();
    frameObserver.onCapturerStarted(false);
    if (eventsHandler != null) {
      eventsHandler.onCameraError("Camera can not be started.");
    }
    return;
  }