Flutter，从函数中显示 AlertDialog

Question

我有以下带有 _checkCreds 函数的代码。我想在按下该按钮时显示警报。

当我用 AlertDialog() 替换 print() 语句时，我收到“未找到 MaterialLocalizations”。

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState(); 
}

class _MyAppState extends State<MyApp> {
  void _checkCreds(bool val) {
    if(!val){
      print("Warning, show alert here instead of print!");
      return;
    }
    ...
    // Continue executing
  }

  Widget build(BuildContext context) {
    return MaterialApp(
      home: RaisedButton(
        child: "Press me to trigger an alert!" ),
        onPressed: () => _checkCreds(false),
    );   
  } 

}

Answer 1

我已经弄清楚了，因为我不知道“BuildContext”适合所有这些的 React 环境。经过进一步调查，我将当前上下文作为参数传递给调用警报的函数。

在 main() 之上：

Future<void> _ackAlert(BuildContext context) {
  return showDialog<void>(
    context: context,
    builder: (BuildContext context) {
      return AlertDialog(
        title: Text('Error'),
        content: const Text('Please enter a valid text'),
        actions: <Widget>[
          FlatButton(
            child: Text('Okay'),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
        ],
      );
    },   
  ); 
}

在主要小部件内：

Widget build(BuildContext context) {
    return MaterialApp(
      home: RaisedButton(
        child: "Press me to trigger an alert!" ),
        // I've added a parameter that takes the current context
        onPressed: () => _checkCreds(false, context),
    );   
  }

Answer 2

我想这就是你想要的：

void _checkCreds(bool val){//put it inside 'MyAppState' class
  if(!val){
    showDialog(
      barrierDismissible: true,//tapping outside dialog will close the dialog if set 'true'
      context: context, 
      builder: (context){
        return Dialog(
          //Add code here
        );
      }
    );
  }
  ...
  // Continue executing
}

AlertDialog 和 Dialog 具有相同的属性，除了 AlertDialog 具有 content 属性而 Dialog 具有 child 属性。两者做同样的工作。

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