title: How to move element anywhere inside parent container with drag and drop in Flutter?
body: <p>I'm using the Draggable widget in Flutter, and I want to move my element anywhere inside a parent widget.</p>
  
  <p>I tried the dragtarget widget, but I couldn't set it to my parent widget. I also tried the <code>onDraggableCanceled</code> method of the Draggable widget for getting the offset, and applied it for the new offset of the element, but it gives me the offset from the device, not from the parent container. </p>
  
  <p>So, what is the right way of doing this?</p>