"setState() or MarkNeedsBuild() called during" flutter 应用程序出错

Question

我是 flutter 的初学者。当我调用 Settings widget 时，出现以下错误。我尝试了同一期发布的所有内容，但没有任何改变。当我删除 StreamBuilder 时，它工作正常。但是，如果没有 StreamBuilder，我无法从 Cloud firestore 获取数据并将其显示在设置小部件中。

这是主屏幕，我在其中调用 Settings widget。

body: FlatButton.icon(
            onPressed: () {
              Navigator.of(context)
                  .push(MaterialPageRoute(builder: (context) => Settings()));
            },
            icon: Icon(Icons.settings),
            label: Text('User Profile')),
      );

这是设置小部件

import 'dart:math';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:flutter_firebase_test/screens/services/auth.dart';
import 'package:flutter_firebase_test/shared/loading.dart';

class Settings extends StatefulWidget {
  @override
  _Settings createState() => _Settings();
}

class _Settings extends State<Settings> {
  AuthService _auth = new AuthService();
  @override
  Widget build(BuildContext context) {
    Color randomColor() {
      int index = 0;
      List colors = [
        Colors.red,
        Colors.blue,
        Colors.green,
        Colors.yellow,
        Colors.amber,
        Colors.deepPurple
      ];
      Random rnd = new Random();
      setState(() => index = rnd.nextInt(6));
      return colors[index];
    }

    return StreamBuilder<QuerySnapshot>(
        stream: Firestore.instance.collection('users').snapshots(),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return Loading();
          } else {
            return Scaffold(
              body: Container(
                padding: EdgeInsets.fromLTRB(30, 80, 30, 0),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Center(
                      child: Column(
                        children: [
                          CircleAvatar(
                            backgroundColor: randomColor(),
                            //backgroundImage: AssetImage('assets/avatars/male1.jpg'),
                            radius: 60,
                            child: Text(
                              // TODO: The name will be set later!
                              "Ali"[0].toUpperCase(),
                              style: TextStyle(
                                color: Colors.black,
                                fontWeight: FontWeight.bold,
                                fontSize: 40,
                              ),
                            ),
                          ),
                          SizedBox(
                            height: 20,
                          ),
                          Text("dasdas"),
                        ],
                      ),
                    ),
                    SizedBox(
                      height: 30,
                    ),
                    Divider(
                      color: Colors.black,
                    ),
                    SizedBox(
                      height: 40,
                    ),
                    Wrap(children: [
                      Text(
                        "Name:",
                        style: TextStyle(
                          fontSize: 20,
                        ),
                      ),
                      SizedBox(
                        width: 20,
                      ),
                    ]),
                    SizedBox(
                      height: 40,
                    ),
                    Wrap(children: [
                      Text(
                        "Username:",
                        style: TextStyle(
                          fontSize: 20,
                        ),
                      ),
                      SizedBox(
                        width: 20,
                      ),
                      Text(
                        "User fullname will display here",
                        style: TextStyle(
                          fontSize: 20,
                        ),
                      ),
                    ]),
                  ],
                ),
              ),
            );
          }
        });
  }
}

flutter doctor -v 结果

] Flutter (Channel stable, 1.22.5, on Microsoft Windows [Version 10.0.19042.685], locale en-US)
    • Flutter version 1.22.5 at C:\src\flutter
    • Framework revision 7891006299 (3 weeks ago), 2020-12-10 11:54:40 -0800
    • Engine revision ae90085a84
    • Dart version 2.10.4       

 
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at C:\Users\demir\AppData\Local\Android\sdk
    • Platform android-30, build-tools 30.0.2
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
    • All Android licenses accepted.

调试控制台：

The following assertion was thrown building StreamBuilder<QuerySnapshot>(dirty, state: _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot<QuerySnapshot>>#778da):
setState() or markNeedsBuild() called during build.
This Settings widget cannot be marked as needing to build because the framework is already in the process of building widgets.  A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.

    state: _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot<QuerySnapshot>>#778da
The relevant error-causing widget was
StreamBuilder<QuerySnapshot>
package:flutter_firebase_test/…/home/settings.dart:31
When the exception was thrown, this was the stack
#0      Element.markNeedsBuild.<anonymous closure>
package:flutter/…/widgets/framework.dart:4292
#1      Element.markNeedsBuild
package:flutter/…/widgets/framework.dart:4307
#2      State.setState
package:flutter/…/widgets/framework.dart:1264
#3      _Settings.build.randomColor
package:flutter_firebase_test/…/home/settings.dart:27
#4      _Settings.build.<anonymous closure>
package:flutter_firebase_test/…/home/settings.dart:47
...

Answer 1

将您的 randomColor 方法放在 build 方法之外。此外，您不需要在索引变量上调用 setState，因为它在该方法中是本地的

Color randomColor() {
  int index = 0;
  List colors = [
    Colors.red,
    Colors.blue,
    Colors.green,
    Colors.yellow,
    Colors.amber,
    Colors.deepPurple
  ];
  Random rnd = new Random();
  index = rnd.nextInt(6);
  return colors[index];
}

// ...

@override
Widget build(BuildContext context) {

"setState() or MarkNeedsBuild() called during" flutter 应用程序出错

"setState() or MarkNeedsBuild() called during" error in flutter app

android

firebase

flutter

google-cloud-firestore

stream-builder