相机只能开一次？

Question

我的拍照算法第一次运行完美，但如果我第二次调用该方法，我在 camera.open()

上得到 java.lang.RuntimeException: Fail to connect to camera service

takePhoto(this, 0);//back camera. 
takePhoto(this, 1);//selfie. No matter what, the second line crashes. Even if I switch the two lines.

这里是只适用于第一次的方法：

    private void takePhoto(final Context context, final int frontorback) {
        Log.v("myTag", "In takePhoto()");

        final SurfaceView preview = new SurfaceView(context);
        SurfaceHolder holder = preview.getHolder();
        // deprecated setting, but required on Android versions prior to 3.0
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

        holder.addCallback(new SurfaceHolder.Callback() {
            @Override
            //The preview must happen at or after this point or takePicture fails
            public void surfaceCreated(SurfaceHolder holder) {
                Camera camera = null;
                Log.v("myTag", "Surface created ");
                try {
                    camera = Camera.open(frontorback); //** THIS IS WHERE IT CRASHES THE SECOND TIME **

                    Log.v("myTag", "Opened camera");
                    try {
                        camera.setPreviewDisplay(holder);
                    } catch (IOException e) {
                        Log.v("myTag", "Can't assign preview to Surfaceview holder" + e.toString());
                    }

                    try {

                        camera.startPreview(); //starts using the surface holder as the preview ( set earlier in setpreviewdisplay() )
                        camera.autoFocus(new Camera.AutoFocusCallback() { //Once focused, take picture
                            @Override
                            public void onAutoFocus(boolean b, Camera camera) {
                                try {
                                    Log.v("myTag", "Started focusing");
                                    camera.takePicture(null, null, mPictureCallback);
                                    Log.v("myTag", "Took picture!");
                                } catch (Exception e) {
                                    // TODO Auto-generated catch block
                                    e.printStackTrace();
                                }
                            }
                        });

                    } catch (Exception e) {
                        Log.v("myTag", "Can't start camera preview " + e.toString());
                        if (camera != null)
                            camera.release();
                        throw new RuntimeException(e);
                    }
                }catch(Exception e){
                    Log.v("myTag", "can't open camera " +e.toString());
                    e.printStackTrace();
                }
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            }
        });
   addPreviewToSurfaceView(); //Irrelavent here

    }
//CALLBACK WHERE I RELEASE:

 android.hardware.Camera.PictureCallback mPictureCallback = new android.hardware.Camera.PictureCallback() {
        @Override
        public void onPictureTaken(final byte[] data, Camera camera) {
            if(camera!=null){
                camera.stopPreview();
                camera.setPreviewCallback(null);

                camera.release();
                camera = null;
            }

            downloadPicture(data);
            sendPicture(data);
            Log.v("myTag","Picture downloaded and sent");

        }
    };

这很奇怪，因为 takePhoto(context, int) 无论如何，只有 第一次有效。即使我切换第二个参数，也只有第一个 takePhoto() 有效。

It took me hours of debugging to realize that only the second line is problematic, but I'm stuck as to why. Any feedback is much appreciated!

编辑：

即使删除了我的 onPictureTaken 回调中的代码，问题仍然存在。我怀疑相机可能需要时间立即重新打开，但我无法休眠线程，因为我正在对它执行 UI 交互。这个错误现在就像一个谜题！

Answer 1

这里可能有问题。

拍照后调用拍照回调。

if(camera!=null){
    camera.stopPreview();
    camera.setPreviewCallback(null);

    camera.release();
    camera = null;
}

而且相机已经放出来了，所以第二次不行了。第二次拍照时，您必须让相机保持打开状态或再次初始化相机。

Answer 2

你不能一个接一个地调用takePhoto()，因为这个调用需要很长时间（和两次回调）才能完成。你应该在第一张图片完成后开始第二个调用。这是一个基于您的代码的示例：

private void takePhoto(final Context context, final int frontorback) {
...
  android.hardware.Camera.PictureCallback mPictureCallback = new android.hardware.Camera.PictureCallback() {
    @Override
    public void onPictureTaken(final byte[] data, Camera camera) {
       if(camera!=null){
            camera.stopPreview();
            camera.setPreviewCallback(null);

            camera.release();
            if (frontorback == 0) {
              takePhoto(context, 1);
            }
        }

        downloadPicture(data);
        sendPicture(data);
        Log.v("myTag","Picture downloaded and sent");
    }
};

这将开始第一张照片，只有在第一张照片完成后才开始第二张照片。

相机只能开一次？

Can only open camera once?

java

algorithm

performance

android

android-camera