onMove method

String onMove(DragTargetDetails<Object?> details)

Implementation

String onMove(DragTargetDetails<Object?> details) {
  scrollTimer?.cancel();
  scrollTimer = null;
  var scrollArea = 70.0;
  var dy = details.offset.dy - parentOffset!.dy;
  if (dy < scrollArea) {
    var jump = (scrollArea - max(dy, 0));
    scrollTimer ??= Timer.periodic(const Duration(milliseconds: 50), (timer) {
      try {
        if (verticalScrollController!.offset >
            verticalScrollController!.position.minScrollExtent) {
          verticalScrollController
              ?.jumpTo(verticalScrollController!.offset - jump);
        }
      } catch (ex) {/*Nothing to Do*/}
    });
  } else if (dy > (parentHeight - scrollArea)) {
    var jump = (scrollArea - (parentHeight - dy));
    scrollTimer ??= Timer.periodic(const Duration(milliseconds: 50), (timer) {
      try {
        if (verticalScrollController!.offset <
            verticalScrollController!.position.maxScrollExtent) {
          verticalScrollController
              ?.jumpTo(verticalScrollController!.offset + jump);
        }
      } catch (ex) {/*Nothing to Do*/}
    });
  }

  //For Debugging
  var f = NumberFormat("###,##0.0", "de_DE");
  return " offset: ${f.format(dy)} parentHeight: ${f.format(parentHeight)}";
}