错误：

PS E:\project\AccountManage\android> npm run android

> AccountManage@0.0.1 android
> react-native run-android   

info A dev server is already running for this project on port 8081.
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info Launching emulator...
error Failed to launch emulator. Reason: No emulators found as an output of `emulator -list-avds`.
warn Please launch an emulator manually or connect a device. Otherwise app may fail to launch.
info Installing the app...

> Task :app:installDebug
Installing APK 'app-debug.apk' on 'Medium_Phone_API_31(AVD) - 12' for :app:debug
Installed on 1 device.

BUILD SUCCESSFUL in 6s
43 actionable tasks: 2 executed, 41 up-to-date
info Connecting to the development server...
warn Failed to connect to development server using "adb reverse": spawnSync C:\Users\ASUS\AppData\Local\Android\platform-tools\adb ENOENT
info Starting the app...                                                                                                                 
系统找不到指定的路径。
error Failed to start the app.
Error: Command failed with exit code 1: C:\Users\ASUS\AppData\Local\Android\platform-tools\adb shell am start -n com.accountmanage/com.accountmanage.MainActivity -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
    at makeError (E:\project\AccountManage\node_modules\execa\lib\error.js:60:11)
    at module.exports.sync (E:\project\AccountManage\node_modules\execa\index.js:194:17)
    at tryLaunchAppOnDevice (E:\project\AccountManage\node_modules\@react-native-community\cli-platform-android\build\commands\runAndroid\tryLaunchAppOnDevice.js:52:22)
    at E:\project\AccountManage\node_modules\@react-native-community\cli-platform-android\build\commands\runAndroid\runOnAllDevices.js:93:39
    at Array.forEach (<anonymous>)
    at runOnAllDevices (E:\project\AccountManage\node_modules\@react-native-community\cli-platform-android\build\commands\runAndroid\runOnAllDevices.js:88:48)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async Command.handleAction (E:\project\AccountManage\node_modules\@react-native-community\cli\build\index.js:118:9)
info Run CLI with --verbose flag for more details.

解决方法：

        我是因为android sdk的环境变量没配好

1.找到sdk所在位置

2.配置环境变量

        创建新的变量

ANDROID_HOME

         添加到path中

%ANDROID_HOME%\tools\bin

%ANDROID_HOME%\tools

%ANDROID_HOME%\emulator

%ANDROID_HOME%\platform-tools

        然后重启下 AndroidStudio 就能启动项目了