Btukfyl

I have a map of nodes and a circle that can be moved around the nodes using drag and drop. However, after a node has been used and the circle is moved it can no longer be moved back to the same node unless I rotate the screen, resetting everything. Why is this the case?

Secondly on a practical level, do I need to recreate the used component after each successful drop or how should I resolve this issue?

I'm using observables to update the UI:

private void handleObservedCheckers() {

    mainViewModel.checkerLiveData.observe(this, new Observer<Collection<Checker>>() {

        @Override

        public void onChanged(@Nullable Collection<Checker> checkers) {

            if (checkers == null)

                return;

            Log.d(TAG, checkers.toString());

            for (Checker checker : checkers) {

                CheckerView view = (CheckerView) nodeMap.get(checker.getPosition());

                view.invalidate();

                if (checker.getColor() == Color.RED) {

                    view.paintRed();

                    view.show();

                }

                else if (checker.getColor() == Color.BLUE) {

                    view.paintBlue();

                    view.show();

                } else {

                    view.hide();

                }

                view.draggable = checker.isDraggable();

                //view.invalidate();

            }

        }

    });

}

And the view component is created onCreate

private View createChecker(int x, int y, int size, Position position) {

    final CheckerView view = new CheckerView(this, x, y, size, position);

    view.show();

    view.draggable = false;

    // Maps the view to the given position

    nodeMap.put(position, view);

    checkerViewList.add(view);

    Log.d(TAG, "created: " + view.toString());



    view.setOnTouchListener(new View.OnTouchListener() {

        @Override

        public boolean onTouch(View v, MotionEvent event) {

            if (view.draggable && event.getAction() == MotionEvent.ACTION_DOWN) {

                // Save the position as clip data to be retrieved on drop

                ClipData.Item item = new ClipData.Item("" + view.position);

                ClipData data = new ClipData("", new String{ClipDescription.MIMETYPE_TEXT_PLAIN}, item);

                // Start drag

                View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);

                view.startDragAndDrop(data, shadowBuilder, view, 0);

                return true;

            } else {

                return false;

            }

        }

    });

    view.setOnDragListener(new View.OnDragListener() {

        @Override

        public boolean onDrag(View v, DragEvent event) {

            switch (event.getAction()) {

                case DragEvent.ACTION_DRAG_STARTED:

                    return true;

                case DragEvent.ACTION_DRAG_EXITED:

                    return true;

                case DragEvent.ACTION_DRAG_LOCATION:

                    return true;

                case DragEvent.ACTION_DRAG_ENTERED:

                    return true;

                case DragEvent.ACTION_DROP:

                    Log.w(TAG, "dropped");

                    // get stored position inside clip data if any exists

                    String data = (String) event.getClipData().getItemAt(0).getText();

                    if (!data.equals("")) {

                        mainViewModel.moveChecker(Position.valueOf(data), view.position);

                    } else {

                        mainViewModel.placeChecker(view.position);

                    }



                    return true;

                case DragEvent.ACTION_DRAG_ENDED:

                    return true;

                default:

                    return true;

            }

        }

    });

    return view;

}

I changed to redraw on each cycle, this time I constantly get "Reporting drop result: false" instead. (Ref: https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/view/ViewRootImpl.java)

The problem with attaching a drag listener to the same component as the on touch listner (for shadow drag) is that it will only be able to register drops onto itself it seems...