Android takePicture失败，因为同时拍摄多张照片？

Question

在onCreate方法中，我来自Android Developer网站上的Camera API示例：

  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.content_main);

        getPermission();

        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);


        senSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);        

        mCamera = getCameraInstance();
        mPreview = new CameraPreview(this, mCamera);
        preview.addView(mPreview);

         mPicture = new Camera.PictureCallback() {

            @Override
            public void onPictureTaken(byte[] data, Camera camera) {

                File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
                if (pictureFile == null) {
                    Log.d("NullException", "Error creating media file, check storage permissions");
                    return;
                }

                try {
                    FileOutputStream fos = new FileOutputStream(pictureFile);
                    fos.write(data);
                    fos.close();

                } catch (FileNotFoundException e) {
                    Log.d("FileNotFoundException", "File not found: " + e.getMessage());
                } catch (IOException e) {
                    Log.d("IOException", "Error accessing file: " + e.getMessage());
                }
                safeToTakePicture = true;
            }
        };

        Button captureButton = (Button) findViewById(R.id.button_start);
        captureButton.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        // get an image from the camera
                        while(!safeToTakePicture) {
                        }
                        safeToTakePicture = false;
                        mCamera.takePicture(null, null, mPicture);



                    }
                }
        );

    }

似乎onCreate（）中的takePicture（）有效，但onSensorChanged方法中却无效。当我从onSensorChanged方法中删除了takePicture（）时，没有错误，并且仍然拍摄了图片：

  @Override
    public void onSensorChanged(SensorEvent event) {
        Sensor mySensor = event.sensor;

        if (mySensor.getType() == Sensor.TYPE_LINEAR_ACCELERATION) {

                while(!safeToTakePicture) {
                }
                safeToTakePicture = false;
                mCamera.takePicture(null, null, mPicture);

         }
    }

这是由onSensorChanged（）中的takePicture（）引起的错误日志：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.lawrence.focusrangefinder, PID: 23989
    java.lang.RuntimeException: takePicture failed
        at android.hardware.Camera.native_takePicture(Native Method)
        at android.hardware.Camera.takePicture(Camera.java:1448)
        at android.hardware.Camera.takePicture(Camera.java:1393)
        at com.example.lawrence.focusrangefinder.MainActivity.onSensorChanged(MainActivity.java:157)
        at android.hardware.SystemSensorManager$SensorEventQueue.dispatchSensorEvent(SystemSensorManager.java:964)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:325)
        at android.os.Looper.loop(Looper.java:142)
        at android.app.ActivityThread.main(ActivityThread.java:6938)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

这是onCreate中使用的CameraPreview类，尽管我认为这并不重要：

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d("Error", "Error setting camera preview: " + e.getMessage());
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (mHolder.getSurface() == null){
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
            // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d("Error", "Error starting camera preview: " + e.getMessage());
        }
    }
}

我不确定为什么会这样，我认为这与同时拍摄多张图片有关，因为onSensorChanged被多次调用。我看着这个问题：java.lang.RuntimeException: takePicture failed，我添加了一个变量来阻止这种情况的发生，但仍然无法正常工作。