Question

如何只显示一次警报对话框？我希望在用户首次加载屏幕以显示指令时出现警报对话框。取消对话后，我不希望再次出现。

Answer 1

启动应用程序时，请从共享首选项（例如：isFirstLoaded）中获取值。如果isFirstLoaded == true，则显示对话框。
关闭对话框时，将isFirstLoaded = false设置并保存到共享首选项。

下面是一个示例（请注意，该示例在点击“返回”键时不会处理dismiss事件）。

将shared_preferences添加到您的pubspec.yaml

shared_preferences：^ 0.5.1 + 1

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() {
  runApp(MyStatelessApp());
}

class MyStatelessApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Stateless Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: StatelessWidgetDemo(),
    );
  }
}

class StatelessWidgetDemo extends StatelessWidget {
  final keyIsFirstLoaded = 'is_first_loaded';

  @override
  Widget build(BuildContext context) {
    Future.delayed(Duration.zero, () => showDialogIfFirstLoaded(context));
    return SafeArea(
        child: Scaffold(
            appBar: AppBar(
              title: Text('Flutter Stateless Demo'),
            ),
            body: Center(
              child: Text('Hello'),
            )));
  }

  showDialogIfFirstLoaded(BuildContext context) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    bool isFirstLoaded = prefs.getBool(keyIsFirstLoaded);
    if (isFirstLoaded == null) {
      showDialog(
        context: context,
        builder: (BuildContext context) {
          // return object of type Dialog
          return AlertDialog(
            title: new Text("Title"),
            content: new Text("This is one time dialog"),
            actions: <Widget>[
              // usually buttons at the bottom of the dialog
              new FlatButton(
                child: new Text("Dismiss"),
                onPressed: () {
                  // Close the dialog
                  Navigator.of(context).pop();
                  prefs.setBool(keyIsFirstLoaded, false);
                },
              ),
            ],
          );
        },
      );
    }
  }
}

Flutter中的一次警报对话框

1 个答案: