'Set<Row>' 类型的值不能分配给 'Widget' 类型的变量

Question

在 运行 之后我的小部件树中：

List<List<Widget>> widgets;
/***/
Column(
  children: [
    for (List<Widget> range in (widgets as List<List<Widget>>)) {
      Row(children: range),
    }
  ]
)

我收到这个错误：

Error: A value of type 'Set<Row>' can't be assigned to a variable of type 'Widget'.

Answer 1

使用此删除{ 用于 FOR 循环括号

 for (List<Widget> range in (widgets as List<List<Widget>>))
        Row(children: range),

Set or map? The syntax for map literals is similar to that for set literals. Because map literals came first, {} defaults to the Map type. If you forget the type annotation on {} or the variable it’s assigned to, then Dart creates an object of type Map<dynamic, dynamicdart tour

提示

我们也可以这样使用

Column(children: [
      ...widgets.map((e) {
        return Row(children: e);
      }),
      
    ]);

Answer 2

那是因为您试图将 [[...]] 之类的东西影响到子列而不是 []，请尝试这样的东西：

Column(children: widgets.map(element) => Row(children: element));