java.lang.RuntimeException：无法连接到摄像头服务OnPause和OnResume

Question

我正在开发相机应用程序。在调用OnResume()后调用onPause()时，它会出现以下异常：

  

04-07 17：46：35.374 3674-4562 / com.joltatech.videowatermark W / CameraBase：连接到相机时出错：0   04-07 17：46：35.374 3674-4562 / com.joltatech.videowatermark A / VideoCaptureActivity：无法获取相机                                                                                     java.lang.RuntimeException：无法连接到摄像头服务                                                                                         在android.hardware.Camera.native_setup（本机方法）                                                                                         在android.hardware.Camera。（Camera.java:421）                                                                                         在android.hardware.Camera.open（Camera.java:382）                                                                                         at com.joltatech.videowatermark.VideoCaptureActivity $ 17.doInBackground（VideoCaptureActivity.java:770）                                                                                         at com.joltatech.videowatermark.VideoCaptureActivity $ 17.doInBackground（VideoCaptureActivity.java:765）                                                                                         在android.os.AsyncTask $ 2.call（AsyncTask.java:288）                                                                                         在java.util.concurrent.FutureTask.run（FutureTask.java:237）                                                                                         在android.os.AsyncTask $ SerialExecutor $ 1.run（AsyncTask.java:231）                                                                                         at java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1112）                                                                                         at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:587）                                                                                         在java.lang.Thread.run（Thread.java:841）

public static Camera checkForCamera(){
    Camera camera = null;
    try {
        camera = Camera.open(); // this line will throw exception if camera is not in use.
    }
    catch (Exception e){
        // if exception is thrown, return your boolean value here...
    }
    return camera; // if instance of camera, if it is not available it will return null.
}

  void releaseCamera() {
    if (this.camera != null) {
        this.camera.lock(); // unnecessary in API >= 14
        this.camera.stopPreview();
        this.camera.release();
        this.camera = null;
        this.cameraPreviewFrame.removeView(this.cameraPreview);
    }
}

void releaseMediaRecorder() {
    if (this.mediaRecorder != null) {
        this.mediaRecorder.reset(); // clear configuration (optional here)
        this.mediaRecorder.release();
        this.mediaRecorder = null;
    }
}

void releaseResources() {
    this.releaseMediaRecorder();
    if(checkForCamera()!=null)
    this.releaseCamera();
}

@Override
public void onPause() {
    this.releaseResources();
    super.onPause();
}

  @Override
protected void onResume() {
    super.onResume();

    // initialize the camera in background, as this may take a while
    new AsyncTask<Void, Void, Camera>() {

        @Override
        protected Camera doInBackground(Void... params) {
            try {
                Camera camera = Camera.open();
                return camera == null ? Camera.open(0) : camera;
            } catch (RuntimeException e) {
                Log.wtf(TAG, "Failed to get camera", e);
                return null;
            }
        }

        @Override
        protected void onPostExecute(Camera camera) {
            if (camera == null) {
                Toast.makeText(VideoCaptureActivity.this, "Cannot record video.",
                        Toast.LENGTH_SHORT);
            } else {
                VideoCaptureActivity.this.initCamera(camera);
            }
        }
    }.execute();}

void initCamera(Camera camera) {
    // we now have the camera
    this.camera = camera;
    Camera.Parameters params = camera.getParameters();
    if (params.getSupportedFocusModes().contains(
            Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO)) {
        params.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);
    }
    this.camera.setParameters(params);
    // create a preview for our camera
    this.cameraPreview = new CameraPreview(VideoCaptureActivity.this, this.camera);
    // add the preview to our preview frame
    this.cameraPreviewFrame.addView(this.cameraPreview, 0);
    // enable just the record button
    this.recordButton.setEnabled(true);
}