颤振错误:每个孩子必须恰好布置一次.关于建筑布局 [英] Flutter error: Each child must be laid out exactly once. On building layout

问题描述

我正在使用flutter_bloc.

I'm using flutter_bloc.

我有这样的代码:

class Settings extends StatelessWidget {
  final _formKey = GlobalKey<FormState>();
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
          title: new Text("SomeApp",style: TextStyle(color: Colors.white)),
          automaticallyImplyLeading: false,
          backgroundColor: myBlue.shade50,

          actions: <Widget>[
            IconButton(
              icon: new Icon(FontAwesomeIcons.download,color:  Colors.white),
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => DownloadView()),
                );
              },
            ),
            IconButton(
              icon: new Icon(FontAwesomeIcons.chevronCircleLeft,color:  Colors.white),
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => MainWindow()),
                );
              },
            ),]
      ),
      body: Container(
        padding: EdgeInsets.symmetric(vertical: 16),
        alignment: Alignment.center,
        child: new BlocBuilder<SettingsBloc, SettingsState>(
          builder: (context, state) {
            if (state is SettingsNotLoaded) {
              return new Center(
                  child: Text(
                    'count1',
                    style: TextStyle(fontSize: 24.0,color: Colors.black),
                  )
              );
            } else if (state is SettingsLoaded) {  
              return new Center(
                  child: Text(
                    'count2',
                    style: TextStyle(fontSize: 24.0,color: Colors.black),
                  )
              );
            }
            else
              {
                return new Center(
                    child: Text(
                      'count3',
                      style: TextStyle(fontSize: 24.0,color: Colors.black),
                    )
                );
              }
          },
        ),

      ),
    );
  }

当启动我的应用程序时，我看到了我想要的 appBar，但我没有看到正文中的任何文本(我应该看到 count1、count2 或 count3)，但我得到了错误:

And when starting my app I see the appBar just the way I want, but I do not see any text in body (I should see either count1, count2 or count3), but instead I get the error:

每个孩子必须恰好布置一次."参考第 5 行 - return new Scaffold(

Each child must be laid out exactly once." referring to line 5 - return new Scaffold(

当然，我在 https://flutter 上查找了 flutter_bloc 页面上的信息.dev/docs/development/ui/layout/tutorial ，在此处和在 google 中也是如此.

Of course, I looked for info on flutter_bloc page, on https://flutter.dev/docs/development/ui/layout/tutorial ,here and in google as well.

推荐答案

我只是遇到了同样的问题，我认为它只是颤振中的一个错误.停止并重新安装您的应用

I just had the same problem I think its just a bug in flutter. Stop and then reinstall your app

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