Flutter - 在 AlertDialog 小部件之外点击后关闭系统键盘

Posted 2023-02-23

【中文标题】Flutter - 在 AlertDialog 小部件之外点击后关闭系统键盘

【英文标题】：Flutter - Dismiss system keyboard after tapping outside of AlertDialog widget

【发布时间】：2021-09-25 16:30:15

【问题描述】：

我有一个 AlertDialog 小部件，它有一个 TextField 小部件作为孩子。我已将 AlertDialog 小部件配置为当用户在其外部点击时不会关闭。当用户点击 TextField 时，系统键盘会打开。当用户在 AlertDialog 之外点击时，我想隐藏系统键盘。我正在使用的当前 GestureDetector 仅在用户点击 AlertDialog 时关闭键盘，但在 TextField 之外。我正在寻求的行为是否可以在 Flutter 中实现？我创建了一个全新的 Flutter 应用，并仅包含了相关代码来说明下面的用例。

ma​​in.dart

import 'package:flutter/material.dart';

void main() 
  runApp(MyApp());


class MyApp extends StatelessWidget 
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) 
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  


class MyHomePage extends StatefulWidget 
  MyHomePage(Key? key, required this.title) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();


class _MyHomePageState extends State<MyHomePage> 
  int _counter = 0;

  void _incrementCounter() 
    setState(() 
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    );
  

  @override
  Widget build(BuildContext context) 
    WidgetsBinding.instance!.addPostFrameCallback((_) async 
      await showDialog<String>(
        context: context,
        barrierDismissible: false,
        builder: (BuildContext context) => WillPopScope(
          onWillPop: () async => false,
          child: GestureDetector(
            onTap: () => FocusManager.instance.primaryFocus?.unfocus(),
            child: AlertDialog(
              content: Column(
                mainAxisSize: MainAxisSize.min,
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  TextField(),
                ],
              ),
            ),
          ),
        ),
      );
    );

    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  

【参考方案1】：

基本上，Flutter 中的任何 Dialog 都是在当前对话框之上打开的 Route。 当 barrierDismissible 设置为 true - 点击屏障会触发 Navigator.pop() 方法。

既然您有 WillPopScope - 您可以利用它的 onWillPop 来做您需要的事情：

onWillPop: () async 
            final currentFocus = FocusScope.of(context);
            if (!currentFocus.hasPrimaryFocus && currentFocus.focusedChild != null) 
              FocusManager.instance.primaryFocus?.unfocus();
            

            return false;
          ,

别忘了：

将 barrierDismissible 设置为 true（或删除它，因为它默认为 true） 移除 GestureDetector

【讨论】：

我期待着尝试一下。我试一试后会跟进。感谢您的回答-您给出了非常清晰简洁的解释。干杯! :)