我正在学习在 Flutter 中构建应用程序。现在我来到了警报对话框。我以前做过Android and iOS，但是如何在 Flutter 中发出警报呢？

以下是一些相关的问题：

• 如何在 Flutter 中设置 AlertDialog 操作的样式
• 在 flutter 的警报对话框中添加下拉菜单
• 在应用程序主屏幕上自动加载显示警报对话框
• 如何在flutter中刷新alertdialog
• 颤动中带有圆角的警报对话框

我想做一个更一般的规范问答，所以我的答案如下。

一键式

showAlertDialog(BuildContext context) {

  // set up the button
  Widget okButton = TextButton(
    child: Text("OK"),
    onPressed: () { },
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("My title"),
    content: Text("This is my message."),
    actions: [
      okButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

两个按钮

showAlertDialog(BuildContext context) {

  // set up the buttons
  Widget cancelButton = TextButton(
    child: Text("Cancel"),
    onPressed:  () {},
  );
  Widget continueButton = TextButton(
    child: Text("Continue"),
    onPressed:  () {},
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("AlertDialog"),
    content: Text("Would you like to continue learning how to use Flutter alerts?"),
    actions: [
      cancelButton,
      continueButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

三个按钮

showAlertDialog(BuildContext context) {

  // set up the buttons
  Widget remindButton = TextButton(
    child: Text("Remind me later"),
    onPressed:  () {},
  );
  Widget cancelButton = TextButton(
    child: Text("Cancel"),
    onPressed:  () {},
  );
  Widget launchButton = TextButton(
    child: Text("Launch missile"),
    onPressed:  () {},
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("Notice"),
    content: Text("Launching this missile will destroy the entire universe. Is this what you intended to do?"),
    actions: [
      remindButton,
      cancelButton,
      launchButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

处理按钮按下操作

The onPressed上面示例中按钮的回调是空的，但您可以添加如下内容：

Widget launchButton = TextButton(
  child: Text("Launch missile"),
  onPressed:  () {
    Navigator.of(context).pop(); // dismiss dialog
    launchMissile();
  },
);

如果您进行回调null，则该按钮将被禁用。

onPressed: null,

补充代码

这是代码main.dart如果您没有运行上面的功能。

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter'),
        ),
        body: MyLayout()),
    );
  }
}

class MyLayout extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: ElevatedButton(
        child: Text('Show alert'),
        onPressed: () {
          showAlertDialog(context);
        },
      ),
    );
  }
}

// replace this function with the examples above
showAlertDialog(BuildContext context) { ... }