React native npm start命令在react native中给出错误

突然，昨天当我通过命令“expo start”启动项目时，它没有启动，收到一条消息expo没有安装。因此，我安装了expo cli

现在我输入了命令“expo start”，但是它给出了错误 它打开Metro builder，但因错误而停止

I have been using /programming react native app since last 2 months.
Always it used to work fine , I could code and run the simulator on my iphone . The environment details are as follows:
EXPO --version 3.1.2 ,     npm -v 6.9.0,     node -v12.4.0

这就是依赖关系

Microsoft Windows [Version 10.0.17134.1006]
(c) 2018 Microsoft Corporation. All rights reserved.

C:\Users\Jituni>cd C:\Users\Jituni\bholmentorworld

C:\Users\Jituni\bholmentorworld>expo start
Starting project at C:\Users\Jituni\bholmentorworld
Expo DevTools is running at http://localhost:19002
Opening DevTools in the browser... (press shift-d to disable)
Error: Can't find react-native in package.json dependencies
Error: React Native is not installed. Please run `npm install` in your project directory.
Couldn't start project. Please fix the errors and restart the project.
Set EXPO_DEBUG=true in your env to view the stack trace.

---

您没有在依赖项中安装react本机

Microsoft Windows [Version 10.0.17134.1006]
(c) 2018 Microsoft Corporation. All rights reserved.

C:\Users\Jituni>cd C:\Users\Jituni\bholmentorworld

C:\Users\Jituni\bholmentorworld>expo start
Starting project at C:\Users\Jituni\bholmentorworld
Expo DevTools is running at http://localhost:19002
Opening DevTools in the browser... (press shift-d to disable)
Error: Can't find react-native in package.json dependencies
Error: React Native is not installed. Please run `npm install` in your project directory.
Couldn't start project. Please fix the errors and restart the project.
Set EXPO_DEBUG=true in your env to view the stack trace.

解决方案

您应该使用expo cli创建新项目

首先运行此命令->

expo init projectname

在此步骤中，选择空白项目选择。 然后您可以看到生成的项目

第二步，合并依赖项。然后运行

npm安装

或

纱线安装

---

LAST，使用

npm start

或

warn start

运行react native项目，请向我提供您的package.json。然后由管理员打开cmd并键入

expo--version

。然后给我世博版。@Dragon White{“main”：“node_modules/expo/AppEntry.js”，“scripts”：{“start”：“expo start”，“android”：“expo start--android”，“ios”：“expo start--ios”，“web”：“expo start--web”，“eject”：“expo eject”}，“依赖项”：{“eslint”：“^6.2.1”，“expo”：“^33.0.0”，“firebase”：“^6.4.0”，“react”：“16.8.3”，“react dom”：“^16.8.6”，“react native手势处理程序”：“^1.2.2”，“react native reanimated”：“^1.0.1”，“react native web”：“^0.11.4”，“react navigation”：“^3.11.1”}，“DevDependences”：{“巴贝尔预设博览会”：“^5.1.1”}，“private”：true}我的意思是，已安装的依赖项包括react native dependency.C:\Users\Jituni\bholmentorworld>expo——版本3.1。2@DragonWhilte，非常感谢您提供的解决方案。不过我有一些问题。1.对不起，我不理解“合并依赖项”的含义”“我该怎么办？2.如果我创建了一个新项目，我可以保留我在原始项目中编写的代码吗？请建议Blank expo项目有package.json，它包含必要的依赖项，因此您可以复制和粘贴您的包设置，然后删除重复的。然后复制和粘贴除package.json之外的所有代码。然后进行第二步。谢谢。我也这样做了，但面临着新的问题。不管怎样，你的回答很有帮助

{
  "dependencies": {
    "eslint": "^6.2.1",
    "expo": "^33.0.0",
    "firebase": "^6.4.0",
    "react": "16.8.3",
    "react-dom": "^16.8.6",
    "react-native-gesture-handler": "^1.2.2",
    "react-native-reanimated": "^1.0.1",
    "react-native-web": "^0.11.4",
    "react-navigation": "^3.11.1"
  }
}