checkbox - flutter :复选框 onChanged

Question

我试图实现一个可以禁用和启用按钮的复选框。但是我被以下错误阻止了:

I/flutter (19999): The following assertion was thrown building DisclaimerPage(dirty, state: DisclaimerPageState#24b3d):
I/flutter (19999): setState() or markNeedsBuild() called during build.
I/flutter (19999): This Overlay widget cannot be marked as needing to build because the framework is already in the
I/flutter (19999): process of building widgets. A widget can be marked as needing to be built during the build phase
I/flutter (19999): only if one of its ancestors is currently building. This exception is allowed because the framework
I/flutter (19999): builds parent widgets before children, which means a dirty descendant will always be built.
I/flutter (19999): Otherwise, the framework might not visit this widget during this build phase.

这是我构建页面的代码:

class DisclaimerPageState extends State<DisclaimerPage> {
  bool checkBoxValue = false;

  @override
  Widget build(BuildContext context) {
    var _floatButtonOnPressed;

    if (checkBoxValue) {
      _floatButtonOnPressed = navToHome();
    }

    return new Scaffold(
      appBar: AppBar(
        title: Text("Disclaimer"),
        leading: Container(),
      ),
      body: Container(
        child: Card(
          child: Column(
            children: <Widget>[
              Text("ADHJASDKHKDAD"),
              Row(
                children: <Widget>[
                  Checkbox(
                      value: checkBoxValue,
                      onChanged: (bool newValue) {
                        setState(() {
                          checkBoxValue = newValue;
                        });
                      }),
                  Text("I understand"),
                ],
              ),
            ],
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton.extended(
        onPressed: _floatButtonOnPressed,
        label: Text("PROCEED"),
        icon: Container(),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
    );
  }

  navToHome() {
    Navigator.push(
      context,
      MaterialPageRoute(
          builder: (context) => ImmunityHomePage(title: 'ImMUnity')),
    );
  }
}

我做错了什么吗？我的复选框实现基于 checkbox.dart 的文档。所以我在这里有点困惑。感谢帮助。非常感谢!

Answer 1

而不是检查 checkBoxValue 和设置 onPressed，你应该在你的 on press 函数中检查 checkBoxValue 然后管理导航。所以首先删除这个

if (checkBoxValue) {
  _floatButtonOnPressed = navToHome();
}

然后更新 float Action 按钮的onPressed为

onPressed: (){navToHome();},

然后更新你的navToHome()函数

navtoHome(){
  if(checkValue){
    //your navigation code here
  }
}