onDragDown method

void onDragDown(
  1. DragDownDetails details
)

Implementation

void onDragDown(DragDownDetails details) {
  /// 按下
  setState(() {
    backgroundOffset = details.localPosition - Offset(widget.areaSize.width / 2, widget.areaSize.height / 2);
    handleOffset = Offset.zero;
  });
}