在满足条件或方法出错时显示 Flutter 警报对话框

在以下代码中，只要中的值TextField不是双精度值，就会显示消息“不是双精度”。这是通过此 Flutter 应用程序中的方法完成的。我希望它们显示在警报对话框中，而不是像这里显示的消息。我该如何实现？谢谢。

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late TextEditingController myController;
  String text = "INIT";

  bool is_double_input(String str) {
    double a = 0.0;
    int exception_caught = 0;
    try {
      a = double.parse(str);
    } catch (e) {
      exception_caught++;
    } finally {
      if (exception_caught == 0) {
        return true;
      } else {
        return false;
      }
    }
  }

  void setMessage(String myStr) {
    // text = myStr;
    if (is_double_input(myStr)) {
      text = myStr;
    } else {
      text = "Not A Double";
    }
  }

  @override
  void initState() {
    super.initState();
    myController = TextEditingController();
  }

  @override
  void dispose() {
    myController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Column(
        children: [
          Expanded(
            child: TextField(
              controller: myController,
              keyboardType: TextInputType.number,
              onChanged: (value) {
                setState(() {
                  setMessage(value);
                });
              },
            ),
          ),
          Expanded(
            child: Text("MESSAGE: ${text}"),
          ),
        ],
      ),
    );
  }
}

更新 01：虽然问题现在已经得到解答，但我还添加了其他代码showDialog来弹出警报对话框，但这不起作用。我必须触摸警报对话框之外的内容才能关闭对话框。有人能帮忙吗？代码如下：

showDialog(
  context: context,
  builder: (context) => AlertDialog(
    title: const Text('Error'),
    content: const Text('Not a Double'),
    actions: [
      TextButton(
        onPressed: () {
          Navigator.of(context).pop;
        },
        child: const Text("Ok"),
      ),
    ],
  ),
);