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

Question

我有一个 AlertDialog 小部件，它有一个 TextField 小部件作为孩子。 我已将 AlertDialog 小部件配置为在用户点击它外部时不关闭。 当用户点击 TextField 时，系统键盘被打开。 当用户在 AlertDialog 之外点击时，我想隐藏系统键盘。 我当前使用的 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 应用程序，并仅包含相关代码来说明下面的用例。

main.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.
    );
  }
}

Answer 1

Flutter 中的任何 Dialog 基本上都是一个在当前对话框之上打开的 Route。
当barrierDismissible设置为true 时——点击barrier 会触发一个Navigator.pop()方法。

既然你有WillPopScope - 你可以利用它的onWillPop来做你需要的事情：

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

            return false;
          },

不要忘记：

1. 将 barrierDismissible 设置为 true（或删除它，因为它默认为 true）
2. 删除手势检测器