如何捕获背景的图像，而无需使用照相机应用 [英] how to capture an image in background without using the camera application

问题描述

我有一个Android应用程序它由一个按钮。
当你点击按钮，图像应该从相机捕获，而无需打开摄像头应用程序（图像应在后台拍摄的）。
如何实现这个功能？
任何建议将是很大的帮助。
感谢很多提前。

I have an android app which consists of a Button.
When you click on Button, an image should be captured from the camera without opening the camera application (the image should be captured in background).
How to implement this feature?
Any suggestions will be of great help.
Thanks a lot in advance.

推荐答案

您必须创建并没有出现在用户的假面视图，然后您可以通过以下code ++实现

You have to create a fake Surface view that doesn't appears to the users and then you can achieve by the following code

public class MainActivity extends Activity {
    public static final int DONE = 1;
    public static final int NEXT = 2;
    public static final int PERIOD = 1;
    private Camera camera;
    private int cameraId = 0;
    private ImageView display;
    private Timer timer;
    SurfaceHolder previewHolder;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        display = (ImageView) findViewById(R.id.imageView1);
        // do we have a camera?
        if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) 
        {
            Toast.makeText(this, "No camera on this device", Toast.LENGTH_LONG)
                    .show();
        } 
        else 
        {
            cameraId = findFrontFacingCamera();
            if (cameraId < 0)
            {
                Toast.makeText(this, "No front facing camera found.",
                        Toast.LENGTH_LONG).show();
            }
            else
            {
                safeCameraOpen(cameraId);
            }
        }
        // THIS IS JUST A FAKE SURFACE TO TRICK THE CAMERA PREVIEW
        // http://stackoverflow.com/questions/17859777/how-to-take-pictures-in-android-
        // application-without-the-user-interface


SurfaceView dummy = new SurfaceView(this);
 previewHolder = dummy.getHolder();

previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
try {
    camera.setPreviewDisplay(previewHolder);
} catch (IOException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}
        /*SurfaceView view = new SurfaceView(this);
        try {
        //  camera.setPreviewDisplay(view.getHolder());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }*/

        Camera.Parameters params = camera.getParameters();
        params.setJpegQuality(100);
        camera.setParameters(params);
        // We need something to trigger periodically the capture of a
        // picture to be processed
        timer = new Timer(getApplicationContext(), threadHandler);
        timer.execute();
    }

    // //////////////////////////////////thread
    // Handler///////////////////////////////////////
    private Handler threadHandler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            switch (msg.what) {
            case DONE:
                camera.startPreview();
                previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
                try {
                    camera.setPreviewDisplay(previewHolder);
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }


                camera.takePicture(null, null, mCall);
                break;
            case NEXT:
                timer = new Timer(getApplicationContext(), threadHandler);
                timer.execute();
                break;
            }
        }
    };
    Camera.PictureCallback mCall = new Camera.PictureCallback() {
        public void onPictureTaken(byte[] data, Camera camera) {
            // decode the data obtained by the camera into a Bitmap
            // display.setImageBitmap(photo);
            Bitmap bitmapPicture = BitmapFactory.decodeByteArray(data, 0,
                    data.length);
            display.setImageBitmap(bitmapPicture);
            Message.obtain(threadHandler, MainActivity.NEXT, "").sendToTarget();
            // Log.v("MyActivity","Length: "+data.length);
        }
    };

    private int findFrontFacingCamera() {
        int cameraId = -1;
        // Search for the front facing camera
        int numberOfCameras = Camera.getNumberOfCameras();
        for (int i = 0; i < numberOfCameras; i++) {
            CameraInfo info = new CameraInfo();
            Camera.getCameraInfo(i, info);
            if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {
                Log.v("MyActivity", "Camera found");
                cameraId = i;
                break;
            }
        }
        return cameraId;
    }

    @Override
    protected void onPause() {
        if (timer != null) {
            timer.cancel(true);
        }
        releaseCamera();
        super.onPause();
    }

    // I think Android Documentation recommends doing this in a separate
    // task to avoid blocking main UI
    private boolean safeCameraOpen(int id) {
        boolean qOpened = false;
        try {
            releaseCamera();
            camera = Camera.open(id);
            qOpened = (camera != null);
        } catch (Exception e) {
            Log.e(getString(R.string.app_name), "failed to open Camera");
            e.printStackTrace();
        }
        return qOpened;
    }

    private void releaseCamera() {
        if (camera != null) {
            camera.stopPreview();
            camera.release();
            camera = null;
        }
    }

}

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