Question

我遇到的挑战与我读过的here类似：

但是，答案并不能解决问题。现在我被困住了。这是我的代码：

if (snapshot.hasData) {
  List<String> zipCodes = List<String>.from(snapshot.data);
  zipCodeValue = zipCodes[0];
  return Center(
    child: Container(
      height: 50,
      child: DropdownButton<String>(
        items: zipCodes.map((String dropDownStringItem) {
          return DropdownMenuItem<String>(
            value: dropDownStringItem,
            child: Text(dropDownStringItem),
          );
        }).toList(),
        onChanged: (String newValueSelected) {
          setState(() {
            zipCodeValue = newValueSelected;
          });
        },
        value: zipCodeValue,
      ),
    ),
  );
}

我按照建议将DropdownButton小部件包装在容器中，但没有解决问题。

我尝试了Stackoverflow问题的其他答案，但没有解决我的问题。

任何帮助将不胜感激。

Answer 1

结果是，我不能在列中包装DropDownButton。我相信挑战是：

When a Column has one or more Expanded or Flexible children, and is placed in another Column, or in a ListView, or in some other context that does not provide a maximum height constraint for the Column, you will get an exception at runtime saying that there are children with non-zero flex but the vertical constraints are unbounded.[As noted here][1]

在Flexible小部件中包装DropDownButton起作用了。

出现异常-“ RenderFlex底部溢出了Infinity像素。”使用DropdownButton时

1 个答案: