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我想以最小的间隔或（如果可能的话）同时制作两个相机。我尝试在服务上实现它，但同步有很多问题。现在我有两个服务，通过前置和后置摄像头拍照。

也许现在有人，如何在一项服务中使用两个摄像头？

public int onStartCommand(Intent intent, int flags, int startId) {

        frontCamera = getCameraInstance(1);

        SurfaceTexture surfaceTexture = new SurfaceTexture(0);

        try {
          frontCamera.setPreviewTexture(surfaceTexture);
          frontParameters = frontCamera.getParameters();

          frontCamera.startPreview();

          frontCamera.takePicture(null, null, frontCameraCall);
          surfaceTexture.release();
        } catch (IOException e) {
          appendToFile(log, "Front camera service preview exception message: " + e + "\n");
          e.printStackTrace();
        }
    return START_REDELIVER_INTENT;
  }
  protected Camera getCameraInstance(int cameraId){

    Camera c = null;
    try {
      do{
        c = Camera.open(cameraId); // atte
mpt to get a Camera instance
      }while (c == null);
    }catch (Exception e){
      // Camera is not available (in use or does not exist)
      Log.e("myLogs", "Camera " + cameraId + " not available! " + e.toString());
    }
    return c; // returns null if camera is unavailable
  }

  Camera.PictureCallback frontCameraCall = new Camera.PictureCallback() {
    public void onPictureTaken(final byte[] data, Camera camera) {
      if (null != camera){
        camera.stopPreview();
        camera.release();
        camera = null;
      }
      FileOutputStream outStream = null;
      try {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMddHHmm");

        String fileName = "Front" + currentDate + "-" + countFormatter(counter) + ".jpg";
        File photo = new File(Environment.getExternalStorageDirectory() + "/UAV/front", fileName);
        if (!photo.getParentFile().exists()) {
          photo.getParentFile().mkdirs();
        }
        outStream = new FileOutputStream(photo);
        outStream.write(data);
        outStream.close();

        camkapa(frontCamera);
      } catch (FileNotFoundException e) {
      } catch (IOException e) {
      }
    }
  };

    protected void camkapa(Camera camera) {
    if (null != camera) {
      camera.release();
      camera = null;
    }
  }

第二次服务的代码相同。现在我的代码捕获错误：

 W/CameraBase﹕ An error occurred while connecting to camera: 0
10-13 11:17:59.808    2493-2493/com:backService D/AndroidRuntime﹕ Shutting down VM
10-13 11:17:59.809    2493-2493/com:backService E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com:backService, PID: 2493
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.hardware.Camera.setPreviewTexture(android.graphics.SurfaceTexture)' on a null object reference
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