Android Move ImageView

Question

I searched the web for a simple solution to freely move an ImageView. I finally found some code that produces the perfect result:

public class MainActivity extends Activity implements View.OnTouchListener {

    private int _xDelta;
    private int _yDelta;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ImageView j = (ImageView)findViewById(R.id.j);

        j.setOnTouchListener(this);

    }

    public boolean onTouch(View view, MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();
        ImageView j = (ImageView)findViewById(R.id.j);
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                _xDelta = (int) (X - j.getTranslationX());
                _yDelta = (int) (Y - j.getTranslationY());
                break;
            case MotionEvent.ACTION_UP:
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                break;
            case MotionEvent.ACTION_POINTER_UP:
                break;
            case MotionEvent.ACTION_MOVE:
                RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view.getLayoutParams();

                j.setTranslationX(X - _xDelta);
                j.setTranslationY(Y - _yDelta);
                break;
        }

        return true;
    }}

Since I don't really know how my code works, I wanted to see if there were better solutions.

Answer 1

Here's the solution i got:

private float xCoOrdinate, yCoOrdinate;

         view.setOnTouchListener(new View.OnTouchListener() {

            Float y1 = 0f, y2 = 0f;

            @Override
            public boolean onTouch(View v, MotionEvent event) {

                Point size = new Point();
            getWindowManager().getDefaultDisplay().getSize(size);        

                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        //xCoOrdinate = view.getX() - event.getRawX();
                        yCoOrdinate = view.getY() - event.getRawY();
                        Float puffer = 0f;
                        y1 = event.getRawY();

                        break;
                    case MotionEvent.ACTION_MOVE:
                        view.animate().y(event.getRawY() + yCoOrdinate).setDuration(0).start();
                        //view.animate().x(event.getRawX() + xCoOrdinate).y(event.getRawY() + yCoOrdinate).setDuration(0).start();
                        break;
                    case MotionEvent.ACTION_UP:
                        y2 = event.getRawY();
                        Float dy = (y2 - y1);


                        if (dy < 0) { 
                            //moved up
                            view.animate().y(size.y / 100 * -40).setDuration(100).start();
                        } else if (dy > 0) {  
                            // moved down
                            view.animate().y(size.y / 2 - view.getHeight() / 2).setDuration(100).start();  
                        }

                        break;
                }

                return false;
            }
        });

Explanation: I only needed motion on y-axis and dectection if moved up or down. It's done by animating the view to the touch, witch has pros and contras (contra: its complicated to detect where view is in space / pro: the view actually moves and doesnt just appear to be somewhere else) but turned out to work best for me and is quite simple. The goal here is to swipe the view up and get it to a desired spot, same as swipe down, back to original position, this is achieved relativ to screen size. To me the code is relative simple and selfexplainatory, but please ask if anything unclear.