leafOnly<T> static method

bool? Function(TreeNode<T> dragNode, TreeNode<T>? targetNode, DropPosition position) leafOnly<T>()

只允许叶子节点拖拽

适用于只允许最底层节点移动的场景，如文件系统中只能移动文件不能移动文件夹

示例：

TolyDraggableTree(
  canDrop: DragRules.leafOnly<MyData>(),
  // ...
)

Implementation

static bool? Function(
        TreeNode<T> dragNode, TreeNode<T>? targetNode, DropPosition position)
    leafOnly<T>() {
  return (dragNode, targetNode, position) => dragNode.isLeaf;
}