How do I take a lot of pictures with no UI or user interaction in android?

Question

Alright so I am working on an app that has to take pictures and send them to a server for processing. I need this for some image recognition that will eventually help control a robot. Basically I need to use the android device as a webcam that sends pictures. I figured out the Sockets part but now after fiddling with some code for a few days I ended up with this:

public class MainActivity extends AppCompatActivity {
public static final String dTag = "DBG";
@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button trg = (Button)findViewById(R.id.trigger_btn);
    trg.setOnClickListener(new Button.OnClickListener(){
        @Override
        public void onClick(View v)
        {
            SurfaceHolder mSurfaceHolder = new SurfaceHolder() {
                @Override
                public void addCallback(Callback callback) {

                }

                @Override
                public void removeCallback(Callback callback) {

                }

                @Override
                public boolean isCreating() {
                    return false;
                }

                @Override
                public void setType(int type) {

                }

                @Override
                public void setFixedSize(int width, int height) {

                }

                @Override
                public void setSizeFromLayout() {

                }

                @Override
                public void setFormat(int format) {

                }

                @Override
                public void setKeepScreenOn(boolean screenOn) {

                }

                @Override
                public Canvas lockCanvas() {
                    return null;
                }

                @Override
                public Canvas lockCanvas(Rect dirty) {
                    return null;
                }

                @Override
                public void unlockCanvasAndPost(Canvas canvas) {

                }

                @Override
                public Rect getSurfaceFrame() {
                    return null;
                }

                @Override
                public Surface getSurface() {
                    return null;
                }
            };
            Camera.PictureCallback mCall = new Camera.PictureCallback()
            {
                @Override
                public void onPictureTaken(byte[] data, Camera camera)
                {
                    ByteArrayInputStream inputStream = new ByteArrayInputStream(data);
                    Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                    ImageView imW = (ImageView)findViewById(R.id.imView);
                    imW.setImageBitmap(bitmap);
                    Log.d(dTag, "" + data.length);
                }
            };
            mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
            Camera mCamera;
            mCamera = Camera.open();
            try {
                mCamera.setPreviewDisplay();
                mCamera.startPreview();
            }
            catch(IOException e){
                Log.d(dTag, "Cam is null!");
            }
            mCamera.takePicture(null, null, mCall);
            mCamera.stopPreview();
            mCamera.release();
        }
    });

}

Now whenever I press the button I see this in the debug log "D/Camera: app passed NULL surface", I assume this is because of mSurfaceHolder which isn't properly declared. If anyone could point to me what the problem is and how to solve it I would be grateful since I don't have a very good understanding of java and can't seem to find anything that works on the internet.

Answer 1

several problems -

1. You have no surface view and surface holder must be obtained from the surface view. You just can not create a "new" for this purpose.

2. You did not pass any surfaceolder in mCamera.setPreviewDisplay(); so system can not decide where to display.

3. Your method local anonymous inner class is just simply wrong.

Tutorial link: http://examples.javacodegeeks.com/android/core/ui/surfaceview/android-surfaceview-example/