进入相机屏幕时出现短错误屏幕

编程问答 2022-08-12

问题描述

我对飞镖游戏比较陌生，并创建了一个使用相机的应用程序。整个应用程序运行正常，我唯一的问题是，每当我进入相机屏幕时，都会收到一秒钟的错误消息。Error_Screen然后，一切正常。前一个屏幕只是一个主屏幕，不会将任何内容传递到相机屏幕。

这是相机屏幕的代码

import 'package:camera/camera.dart';
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:picer/customButtons.dart';

class CameraScreen extends StatefulWidget {
  @override
  _CameraScreenState createState() => _CameraScreenState();
}

class _CameraScreenState extends State<CameraScreen> {
  CameraController _controller;
  List<CameraDescription> _availableCameras;
  List<String> imageList = List<String>();

  @override
  void initState() {
    super.initState();
    _getAvailableCameras();
  }

  // get available cameras
  Future<void> _getAvailableCameras() async {
    WidgetsFlutterBinding.ensureInitialized();
    _availableCameras = await availableCameras();
    _initCamera(_availableCameras.first);
  }

  // init camera
  Future<void> _initCamera(CameraDescription description) async {
    _controller =
        CameraController(description,ResolutionPreset.max,enableAudio: true);

    await _controller.initialize();
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    final size = MediaQuery.of(context).size;

    return Scaffold(
      backgroundColor: Colors.black,body: SafeArea(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.stretch,children: [
            Expanded(
              flex: 7,child: Transform.scale(
                scale: size.width / size.width,child: CameraPreview(_controller),),SizedBox(
              height: 10,Row(
              children: [
                Expanded(child: FileButton(imageList,imageList.length)),Expanded(
                  child: CustomShutterButton(
                    controller: _controller,imageList: imageList,Expanded(
                    child: RawMaterialButton(
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(10),constraints: BoxConstraints.tightFor(
                    width: 70,height: 70,fillColor: Colors.black,onPressed: () {
                    _toggleCameraLens();
                  },child: Icon(
                    Icons.switch_camera,color: Colors.white,)),],);
  }

  void _toggleCameraLens() {
    // get current lens direction (front / rear)
    final lensDirection = _controller.description.lensDirection;
    CameraDescription newDescription;
    if (lensDirection == CameraLensDirection.front) {
      newDescription = _availableCameras.firstWhere((description) =>
          description.lensDirection == CameraLensDirection.back);
    } else {
      newDescription = _availableCameras.firstWhere((description) =>
          description.lensDirection == CameraLensDirection.front);
    }

    if (newDescription != null) {
      _initCamera(newDescription);
    } else {
      print('Asked camera not available');
    }
  }
}

在iPhone上构建它时，出现以下错误消息：

2020-09-02 15:18:48.470182-0400 Runner[3907:853052] Metal API Validation Enabled
2020-09-02 15:18:48.618830-0400 Runner[3907:853246] flutter: Observatory listening on http://127.0.0.1:52998/_vfDFTNQegY=/
2020-09-02 15:18:51.157075-0400 Runner[3907:853235] flutter: ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
2020-09-02 15:18:51.157194-0400 Runner[3907:853235] flutter: The following NoSuchMethodError was thrown building CameraScreen(dirty,dependencies: [MediaQuery],2020-09-02 15:18:51.157220-0400 Runner[3907:853235] flutter: state: _CameraScreenState#0ffaa):
2020-09-02 15:18:51.157242-0400 Runner[3907:853235] flutter: The getter 'value' was called on null.
2020-09-02 15:18:51.157264-0400 Runner[3907:853235] flutter: Receiver: null
2020-09-02 15:18:51.157286-0400 Runner[3907:853235] flutter: Tried calling: value
2020-09-02 15:18:51.157306-0400 Runner[3907:853235] flutter:
2020-09-02 15:18:51.157327-0400 Runner[3907:853235] flutter: Widget creation tracking is currently disabled. Enabling it enables improved error messages. It can
2020-09-02 15:18:51.157607-0400 Runner[3907:853235] flutter: be enabled by passing `--track-widget-creation` to `flutter run` or `flutter test`.
2020-09-02 15:18:51.157754-0400 Runner[3907:853235] flutter:
2020-09-02 15:18:51.157949-0400 Runner[3907:853235] flutter: When the exception was thrown,this was the stack:
2020-09-02 15:18:51.158073-0400 Runner[3907:853235] flutter: #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
2020-09-02 15:18:51.158204-0400 Runner[3907:853235] flutter: #1      _CameraScreenState.build (package:picer/cameraScreen.dart:42:23)
2020-09-02 15:18:51.158403-0400 Runner[3907:853235] flutter: #2      StatefulElement.build (package:flutter/src/widgets/framework.dart:4663:28)
2020-09-02 15:18:51.158583-0400 Runner[3907:853235] flutter: #3      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4546:15)
2020-09-02 15:18:51.158718-0400 Runner[3907:853235] flutter: #4      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
2020-09-02 15:18:51.158834-0400 Runner[3907:853235] flutter: #5      Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.158861-0400 Runner[3907:853235] flutter: #6      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4525:5)
2020-09-02 15:18:51.158914-0400 Runner[3907:853235] flutter: #7      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4710:11)
2020-09-02 15:18:51.158937-0400 Runner[3907:853235] flutter: #8      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4520:5)
2020-09-02 15:18:51.158989-0400 Runner[3907:853235] flutter: ...     Normal element mounting (24 frames)
2020-09-02 15:18:51.159012-0400 Runner[3907:853235] flutter: #32     Element.inflateWidget (package:flutter/src/widgets/framework.dart:3490:14)
2020-09-02 15:18:51.159068-0400 Runner[3907:853235] flutter: #33     MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5991:32)
2020-09-02 15:18:51.159091-0400 Runner[3907:853235] flutter: ...     Normal element mounting (136 frames)
2020-09-02 15:18:51.159115-0400 Runner[3907:853235] flutter: #169    Element.inflateWidget (package:flutter/src/widgets/framework.dart:3490:14)
2020-09-02 15:18:51.159174-0400 Runner[3907:853235] flutter: #170    Element.updateChild (package:flutter/src/widgets/framework.dart:3258:18)
2020-09-02 15:18:51.159196-0400 Runner[3907:853235] flutter: #171    RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:5624:32)
2020-09-02 15:18:51.159221-0400 Runner[3907:853235] flutter: #172    MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6001:17)
2020-09-02 15:18:51.159272-0400 Runner[3907:853235] flutter: #173    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159295-0400 Runner[3907:853235] flutter: #174    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4571:16)
2020-09-02 15:18:51.159315-0400 Runner[3907:853235] flutter: #175    StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
2020-09-02 15:18:51.159334-0400 Runner[3907:853235] flutter: #176    Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.159386-0400 Runner[3907:853235] flutter: #177    StatefulElement.update (package:flutter/src/widgets/framework.dart:4751:5)
2020-09-02 15:18:51.159408-0400 Runner[3907:853235] flutter: #178    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159427-0400 Runner[3907:853235] flutter: #179    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4571:16)
2020-09-02 15:18:51.159447-0400 Runner[3907:853235] flutter: #180    Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.159504-0400 Runner[3907:853235] flutter: #181    ProxyElement.update (package:flutter/src/widgets/framework.dart:4906:5)
2020-09-02 15:18:51.159527-0400 Runner[3907:853235] flutter: #182    _InheritedNotifierElement.update (package:flutter/src/widgets/inherited_notifier.dart:183:11)
2020-09-02 15:18:51.159546-0400 Runner[3907:853235] flutter: #183    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159566-0400 Runner[3907:853235] flutter: #184    SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5881:14)
2020-09-02 15:18:51.159617-0400 Runner[3907:853235] flutter: #185    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159641-0400 Runner[3907:853235] flutter: #186    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4571:16)
2020-09-02 15:18:51.159664-0400 Runner[3907:853235] flutter: #187    StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
2020-09-02 15:18:51.159686-0400 Runner[3907:853235] flutter: #188    Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.159707-0400 Runner[3907:853235] flutter: #189    StatefulElement.update (package:flutter/src/widgets/framework.dart:4751:5)
2020-09-02 15:18:51.159759-0400 Runner[3907:853235] flutter: #190    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159780-0400 Runner[3907:853235] flutter: #191    SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5881:14)
2020-09-02 15:18:51.159800-0400 Runner[3907:853235] flutter: #192    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159819-0400 Runner[3907:853235] flutter: #193    SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5881:14)
2020-09-02 15:18:51.159840-0400 Runner[3907:853235] flutter: #194    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.159893-0400 Runner[3907:853235] flutter: #195    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4571:16)
2020-09-02 15:18:51.159916-0400 Runner[3907:853235] flutter: #196    Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.159935-0400 Runner[3907:853235] flutter: #197    StatelessElement.update (package:flutter/src/widgets/framework.dart:4627:5)
2020-09-02 15:18:51.159955-0400 Runner[3907:853235] flutter: #198    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.160006-0400 Runner[3907:853235] flutter: #199    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4571:16)
2020-09-02 15:18:51.160029-0400 Runner[3907:853235] flutter: #200    Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.160050-0400 Runner[3907:853235] flutter: #201    ProxyElement.update (package:flutter/src/widgets/framework.dart:4906:5)
2020-09-02 15:18:51.160071-0400 Runner[3907:853235] flutter: #202    Element.updateChild (package:flutter/src/widgets/framework.dart:3245:15)
2020-09-02 15:18:51.160094-0400 Runner[3907:853235] flutter: #203    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4571:16)
2020-09-02 15:18:51.160145-0400 Runner[3907:853235] flutter: #204    StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
2020-09-02 15:18:51.160171-0400 Runner[3907:853235] flutter: #205    Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
2020-09-02 15:18:51.160194-0400 Runner[3907:853235] flutter: #206    BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2667:33)
2020-09-02 15:18:51.160223-0400 Runner[3907:853235] flutter: #207    WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:866:20)
2020-09-02 15:18:51.160274-0400 Runner[3907:853235] flutter: #208    RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:286:5)
2020-09-02 15:18:51.160301-0400 Runner[3907:853235] flutter: #209    SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
2020-09-02 15:18:51.160322-0400 Runner[3907:853235] flutter: #210    SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1056:9)
2020-09-02 15:18:51.160345-0400 Runner[3907:853235] flutter: #211    SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:972:5)
2020-09-02 15:18:51.160397-0400 Runner[3907:853235] flutter: #215    _invoke (dart:ui/hooks.dart:253:10)
2020-09-02 15:18:51.160425-0400 Runner[3907:853235] flutter: #216    _drawFrame (dart:ui/hooks.dart:211:3)
2020-09-02 15:18:51.160446-0400 Runner[3907:853235] flutter: (elided 3 frames from dart:async)
2020-09-02 15:18:51.160467-0400 Runner[3907:853235] flutter:
2020-09-02 15:18:51.160501-0400 Runner[3907:853235] flutter: ════════════════════════════════════════════════════════════════════════════════════════════════════

有人知道如何解决此问题吗？我真的很感激:)预先非常感谢！

解决方法

好吧，我想我可以通过仅在构建之前检查控制器是否已初始化来解决。

  @override
  Widget build(BuildContext context) {
    if (_controller == null || !_controller.value.isInitialized) {
      return Container();
    }
    return Scaffold(
      backgroundColor: Colors.black,
dartnosuchmethoderror

相关问答

matplotlib报错：AttributeError: module 'backend_interagg' has no attribute 'FigureCanvas'. Did you mean: 'FigureCanvasAgg'?
使用本地python环境可以成功执行 import pandas as pd impor...
gitlab登录失败，报错：This challenge page was accidentally cached by an intermediary and is no longer available.
设置时间 控制面板
后端开发常见错误
错误1：Request method ‘DELETE‘ not supported 错误还原：...
docker常见错误
错误1：启动docker镜像时报错：Error response from daemon:...
idea常见错误
错误1：private field ‘xxx‘ is never assigned 按Alt...
pip安装依赖失败
报错如下，通过源不能下载，最后警告pip需升级版本 Requirem...