Auto-moving image on drag listener

Question

I set a drag listener to an ImageView in my app, but when I click it, I don't want it to center the image based on where I pressed. It does this:

https://gfycat.com/ConstantDisguisedKudu

Basically, if I press on bottom right of the image, it takes where I press as central point and moves image's center point on that exact location. But I don't want it to do that. If I press on bottom right , it shouldn't auto move itself and I can drag the image from that point. I don't think any code is necessary but just in case:

@Override
public boolean onDrag(View v, DragEvent event) {
    switch (event.getAction()) {
        // Signal for the start of drag and drop operation
        case DragEvent.ACTION_DRAG_STARTED: {
            // do nothing
            break;
        }
        // The drag point has entered the bounding box of the View
        case DragEvent.ACTION_DRAG_ENTERED: {
            // do nothing
            break;
        }
        // The user has moved the drag shadow outside the bounding box of the view
        case DragEvent.ACTION_DRAG_EXITED: {
            // do nothing
            break;
        }
        // Drag shadow has been released, the drag point is within the bounding box of the view
        case DragEvent.ACTION_DROP: {
            // Get the image and its position
            ImageView view = (ImageView) event.getLocalState();
            int position = (int) view.getTag(R.id.piece_position);

            /**
             * If it is dropped on the left pane, remove it from its parent and also
             * remove the bitmap at the position and notify the adapter.
             * Add it to the left pane and set the position.
             */
            if (v == puzzlePane) {
                ViewGroup viewgroup = (ViewGroup) view.getParent();
                viewgroup.removeView(view);

                if (position != -1) {
                    pieces.remove(position);
                    mAdapter.notifyDataSetChanged();
                }

                FrameLayout containView = (FrameLayout) v;
                containView.addView(view);
                view.setVisibility(View.VISIBLE);
                view.setTag(R.id.piece_state, "left");
                view.setTag(R.id.piece_position, -1);
                view.setOnLongClickListener(null);
                view.setOnTouchListener(mAdapter);
            } else {
                view.setVisibility(View.VISIBLE);
                view.setTag(R.id.piece_state, "right");
                view.setOnTouchListener(null);
                view.setOnLongClickListener(mAdapter);
            }

            Log.d(MyDragListener.class.getSimpleName(), view.getTag(R.id.piece_state) + "");

            view.setX(event.getX() - (view.getWidth() / 2));
            view.setY(event.getY() - (view.getHeight() / 2));

            break;
        }
        // The drag and drop operation has concluded
        case DragEvent.ACTION_DRAG_ENDED: {
            // do nothing
            break;
        }
    }
    return true;
}

Answer 1

You need to extend View.DragShadowBuilder , and send the location of your finger relative to the continer. Something like that:

//where you trigger the dragging
View yourImage; //

yourImage.setOnTouchListener(new OnTouchListener() {
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        final ClipData dragData = new ClipData("label", new String[]{ClipDescription.MIMETYPE_TEXT_PLAIN}, null);
        startDrag(dragData,  // the data to be dragged
                new MyDragShadowBuilder(v, event.getX(), event.getY()), // the drag shadow builder
                null,
                0          // flags (not currently used, set to 0)
        );
        return true;
    }
});

And the class:

private static class MyDragShadowBuilder extends View.DragShadowBuilder {

    int width, height, relativeX, relativeY;

    public MyDragShadowBuilder(View v, float relativeX,float relativeY) {
        super(v);
        this.relativeX = (int) relativeX;
        this.relativeY = (int) relativeY;
        width = (v.getWidth());
        height = (v.getHeight());
    }

    @Override
    public void onProvideShadowMetrics (@NonNull Point size, @NonNull Point touch){
        size.set(width, height);
        touch.set(relativeX, relativeY);
    }

}