键盘打开时重新创建 StatefulWidget 页面

Question

在我的个人资料页面中，当使用单击编辑图标时有编辑选项我使用布尔条件将文本小部件更改为 TextField 小部件，例如
widget.isUpdate ? new Flexible(child: new TextField()) : Text("Text Widget") 它可以工作，但是当 TextField 聚焦时，键盘在那个时候打开，StatefulWidget 重新创建，所以 Boolean 再次变为 false，然后 Textfield 移动到 Text Widget。只有当页面有 Navigator 推送页面（第二页）时才会发生这种情况

 Navigator.push(context,MaterialPageRoute(builder: (context) => UpdateProfile()))

如果此页面作为默认主页则工作正常。我不知道我做错了什么。

代码：

import 'package:flutter/material.dart';

class UpdateProfile extends StatefulWidget {
  bool isUpdate = false;

  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return UpdateProfileState();
  }
}

class UpdateProfileState extends State<UpdateProfile> {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
          title: Text("Update"),
          elevation: 2.0),
      body: Container(
        width: double.infinity,
        height: double.infinity,
        color: Colors.red,
        margin: const EdgeInsets.all(10.0),
        child: Row(
          children: <Widget>[
            widget.isUpdate ? new Flexible(child: new TextField()) : Text("Text Widget"),
            GestureDetector(
              child: IconTheme(
                  data: IconThemeData(color: Color(0xFFffffff)),
                  child: Icon(Icons.edit)),
              onTap: () {
                setState(() {
                  widget.isUpdate = !widget.isUpdate;
                });
              },
            )
          ],
        ),
      ),
    );
  }
}

问题：

如果我设置为主页，那么工作正常，如下所示

import 'package:expense_manager_app/page/splash_page.dart';
import 'package:expense_manager_app/page/update_profile.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(
      debugShowCheckedModeBanner: false,
      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.
        brightness: Brightness.dark,
        primaryColor: Colors.red[500],
        accentColor: Colors.green[900],
      ),
      home: UpdateProfile(),
    );
  }
}

Answer 1

您应该将变量 isUpdate 移到您的状态中，记住小部件是不可变的。

        class UpdateProfileState extends State<UpdateProfile> {

         bool isUpdate = false;

          @override
          Widget build(BuildContext context) {
            // TODO: implement build
            return Scaffold(
              appBar: AppBar(
                  title: Text("Update"),
                  elevation: 2.0),
              body: Container(
                width: double.infinity,
                height: double.infinity,
                color: Colors.red,
                margin: const EdgeInsets.all(10.0),
                child: Row(
                  children: <Widget>[
                    isUpdate ? new Flexible(child: new TextField()) : Text("Text Widget"),
                    GestureDetector(
                      child: IconTheme(
                          data: IconThemeData(color: Color(0xFFffffff)),
                          child: Icon(Icons.edit)),
                      onTap: () {
                        setState(() {
                          isUpdate = !isUpdate;
                        });
                      },
                    )
                  ],
                ),
              ),
            );
          }
        }

还要更改此：

    Navigator.push(context,MaterialPageRoute(builder: (context) => UpdateProfile()))

为此：

    final page = UpdateProfile();
    Navigator.push(context,MaterialPageRoute(builder: (context) => page ))

Answer 2

因为你设置了默认值 bool isUpdate = false; 把它改成 bool isUpdate;

并使用 State class 的 initState 方法并将 isUpdate 设置为 false。我会被叫一次。

@override
void initState() { 
  widget.isUpdate = false;   
  super.initState();
}

Answer 3

另外，如果你在 didChangeDependencies 方法上做了一些事情，那也会导致

键盘打开时重新创建 StatefulWidget 页面

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