切换按钮，失败的断言行 188 pos 12：'isSelected != null is not true

Question

我目前正在学习 Flutter，我尝试制作一个文本 ToogleButtons，但是我遇到了这个错误：

'package:flutter/src/material/toogle_buttons.dart': Failed assertion: line 188 pos 12: 'isSelected != null': is not true.

我已经将列表 isSelected 的 bool 更改为 [true, false, false]; 但它没有用，

我的代码如下：


  List<bool> isSelected = [false, false, false];
  FocusNode focusNodeButton1 = FocusNode();
  FocusNode focusNodeButton2 = FocusNode();
  FocusNode focusNodeButton3 = FocusNode();
  List<FocusNode> focusToggle;

  @override
  void initState() {
    // ignore: todo
    // TODO: implement initState
    super.initState();
    focusToggle = [focusNodeButton1, focusNodeButton2, focusNodeButton3];
  }

  @override
  void dispose() {
    // Clean up the focus node when the Form is disposed.
    focusNodeButton1.dispose();
    focusNodeButton2.dispose();
    focusNodeButton3.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: <Widget>[
        Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.end,
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.only(left: kDefaultPadding / 2),
              child: ToggleButtons(
                borderColor: Colors.black,
                fillColor: Colors.white,
                borderWidth: 2,
                borderRadius: BorderRadius.circular(2),
                selectedBorderColor: kMaincolor,
                selectedColor: kMaincolor,
                focusNodes: focusToggle,
                children: <Widget>[
                  Padding(
                    padding: EdgeInsets.all(5),
                    child: Text(
                      "Lingkar Teman",
                      style: TextStyle(fontSize: 15),
                    ),
                  ),
                  Padding(
                    padding: EdgeInsets.all(5),
                    child: Text(
                      "Orang Lain",
                      style: TextStyle(fontSize: 15),
                    ),
                  ),
                  Padding(
                    padding: EdgeInsets.all(5),
                    child: Text(
                      "Semua",
                      style: TextStyle(fontSize: 15),
                    ),
                  ),
                ],
                isSelected: isSelected,
                onPressed: (int index) {
                  setState(() {
                    isSelected[index] = !isSelected[index];
                  });
                },
              ),
            ),
          ],
        ),

Answer 1

代码对我来说很好。可能的问题可能是您在运行应用程序之后写了 isSelected 列表，现在您正在尝试热重新加载应用程序，因此它将其视为 null 并且这个问题正在发生。请尝试重新启动应用程序或初始化 isSelected in build.此外，您不能像那样恢复数组的状态，因为您需要检查索引。您可以将setState()内容替换为如下

setState(() {
    for (int i = 0; i < isSelected.length; i++) {
        isSelected[i] = i == index
    }
});

切换按钮，失败的断言行 188 pos 12：'isSelected != null is not true

Toggle Buttons, failed assertion line 188 pos 12: 'isSelected != null is not true

togglebutton

dart

flutter