关闭 Drawer 后重新聚焦 TextField

Question

当用户关闭抽屉时，我想将焦点返回到 TextField。在此处的示例应用程序中（取自 https://flutter.dev/docs/cookbook/design/drawer 并稍作修改）有一个 TextField 具有焦点。打开抽屉，然后通过点击它旁边的来关闭抽屉，但TextField 上的焦点已经消失。

如何将焦点返回到TextField？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  final appTitle = 'Drawer Demo';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: appTitle,
      home: MyHomePage(title: appTitle),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(title)),
      body: Center(child: TextField(autofocus: true)),
      drawer: Drawer(
        // Add a ListView to the drawer. This ensures the user can scroll
        // through the options in the drawer if there isn't enough vertical
        // space to fit everything.
        child: ListView(
          // Important: Remove any padding from the ListView.
          padding: EdgeInsets.zero,
          children: <Widget>[
            DrawerHeader(
              child: Text('Drawer Header'),
              decoration: BoxDecoration(
                color: Colors.blue,
              ),
            ),
            ListTile(
              title: Text('Item 1'),
              onTap: () {
                // Update the state of the app
                // ...
                // Then close the drawer
                Navigator.pop(context);
              },
            ),
            ListTile(
              title: Text('Item 2'),
              onTap: () {
                // Update the state of the app
                // ...
                // Then close the drawer
                Navigator.pop(context);
              },
            ),
          ],
        ),
      ),
    );
  }
}

Answer 1

使用FocusNode 和自定义Drawer 小部件：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  final appTitle = 'Drawer Demo';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: appTitle,
      home: MyHomePage(title: appTitle),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {

    FocusNode fieldNode = FocusNode();

    return Scaffold(
      appBar: AppBar(title: Text(title)),
      body: Center(
          child: Container(
            width: 150.0,
            child: TextField(autofocus: true,focusNode: fieldNode,)
          ),
      ),
      drawer: CustomDrawer(node: fieldNode,),
    );
  }
}

class CustomDrawer extends StatefulWidget {

  final FocusNode node ;

  CustomDrawer({Key key,this.node}): super(key: key);

  @override
  _CustomDrawerState createState() => _CustomDrawerState();
}

class _CustomDrawerState extends State<CustomDrawer> {

  @override
  void initState() {
    super.initState();
    widget.node.unfocus();
  }

  @override
  void dispose() {
    widget.node.requestFocus();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Drawer(
      // Add a ListView to the drawer. This ensures the user can scroll
      // through the options in the drawer if there isn't enough vertical
      // space to fit everything.
      child: ListView(
        // Important: Remove any padding from the ListView.
        padding: EdgeInsets.zero,
        children: <Widget>[
          DrawerHeader(
            child: Text('Drawer Header'),
            decoration: BoxDecoration(
              color: Colors.blue,
            ),
          ),
          ListTile(
            title: Text('Item 1'),
            onTap: () {
              // Update the state of the app
              // ...
              // Then close the drawer
              Navigator.pop(context);
            },
          ),
          ListTile(
            title: Text('Item 2'),
            onTap: () {
              // Update the state of the app
              // ...
              // Then close the drawer
              Navigator.pop(context);
            },
          ),
        ],
      ),
    );
  }
}