DragHandler dragHandler = createDragHandler(currentVerticalPanel);
PickupDragController widgetDragController = new PickupDragController(boundaryPanel, false);
widgetDragController.setBehaviorMultipleSelection(false);
widgetDragController.addDragHandler(dragHandler);
widgetDragController.registerDropController(widgetDropController);
// Add each widget to the VerticalPanel and enable dragging via its DragTarget.
for (T widget : widgets) {
currentVerticalPanel.add(widget);
widgetDragController.makeDraggable(widget, getDragTarget.apply(widget));