我目前正在构建一个react原生应用程序，每次运行时都会收到以下错误消息：react原生运行android
错误消息：
info Running jetifier to migrate libraries to AndroidX. You can disable it using "--no-jetifier" flag.
Jetifier found 1052 file(s) to forward-jetify. Using 8 workers...
info Starting JS server...
info Launching emulator...
error Failed to launch emulator. Reason: Emulator exited before boot..
warn Please launch an emulator manually or connect a device. Otherwise app may fail to launch.
info Installing the app...
> Configure project :react-native-firebase_app
:react-native-firebase_app package.json found at /Users/asakoulas/BODYBOX/Bodybox/node_modules/@react-native-firebase/app/package.json
:react-native-firebase_app:firebase.bom using default value: 28.1.0
:react-native-firebase_app:play.play-services-auth using default value: 19.0.0
:react-native-firebase_app package.json found at /Users/asakoulas/BODYBOX/Bodybox/node_modules/@react-native-firebase/app/package.json
:react-native-firebase_app:version set from package.json: 12.1.0 (12,1,0 - 12001000)
:react-native-firebase_app:android.compileSdk using custom value: 29
:react-native-firebase_app:android.targetSdk using custom value: 29
:react-native-firebase_app:android.minSdk using custom value: 21
:react-native-firebase_app:reactNativeAndroidDir /Users/myuser/appname/appname/node_modules/react-native/android
Mapping new ns http://schemas.android.com/repository/android/common/02 to old ns http://schemas.android.com/repository/android/common/01
Mapping new ns http://schemas.android.com/repository/android/generic/02 to old ns http://schemas.android.com/repository/android/generic/01
Mapping new ns http://schemas.android.com/sdk/android/repo/addon2/02 to old ns http://schemas.android.com/sdk/android/repo/addon2/01
Mapping new ns http://schemas.android.com/sdk/android/repo/repository2/02 to old ns http://schemas.android.com/sdk/android/repo/repository2/01
Mapping new ns http://schemas.android.com/sdk/android/repo/sys-img2/02 to old ns http://schemas.android.com/sdk/android/repo/sys-img2/01
Mapping new ns http://schemas.android.com/repository/android/common/02 to old ns http://schemas.android.com/repository/android/common/01
Mapping new ns http://schemas.android.com/repository/android/generic/02 to old ns http://schemas.android.com/repository/android/generic/01
Mapping new ns http://schemas.android.com/sdk/android/repo/addon2/02 to old ns http://schemas.android.com/sdk/android/repo/addon2/01
Mapping new ns http://schemas.android.com/sdk/android/repo/repository2/02 to old ns http://schemas.android.com/sdk/android/repo/repository2/01
Mapping new ns http://schemas.android.com/sdk/android/repo/sys-img2/02 to old ns http://schemas.android.com/sdk/android/repo/sys-img2/01
Checking the license for package Android SDK Build-Tools 30.0.2 in /Users/username/Library/Android/sdk/licenses
License for package Android SDK Build-Tools 30.0.2 accepted.
Preparing "Install Android SDK Build-Tools 30.0.2 (revision: 30.0.2)".
"Install Android SDK Build-Tools 30.0.2 (revision: 30.0.2)" ready.
Installing Android SDK Build-Tools 30.0.2 in /Users/asakoulas/Library/Android/sdk/build-tools/30.0.2
"Install Android SDK Build-Tools 30.0.2 (revision: 30.0.2)" complete.
"Install Android SDK Build-Tools 30.0.2 (revision: 30.0.2)" finished.
Mapping new ns http://schemas.android.com/repository/android/common/02 to old ns http://schemas.android.com/repository/android/common/01
Mapping new ns http://schemas.android.com/repository/android/generic/02 to old ns http://schemas.android.com/repository/android/generic/01
Mapping new ns http://schemas.android.com/sdk/android/repo/addon2/02 to old ns http://schemas.android.com/sdk/android/repo/addon2/01
Mapping new ns http://schemas.android.com/sdk/android/repo/repository2/02 to old ns http://schemas.android.com/sdk/android/repo/repository2/01
Mapping new ns http://schemas.android.com/sdk/android/repo/sys-img2/02 to old ns http://schemas.android.com/sdk/android/repo/sys-img2/01
WARNING:: The specified Android SDK Build Tools version (28.0.3) is ignored, as it is below the minimum supported version (30.0.2) for Android Gradle Plugin 4.2.2.
Android SDK Build Tools 30.0.2 will be used.
To suppress this warning, remove "buildToolsVersion '28.0.3'" from your build.gradle file, as each version of the Android Gradle Plugin now has a default version of the build tools.
WARNING:: The specified Android SDK Build Tools version (28.0.3) is ignored, as it is below the minimum supported version (30.0.2) for Android Gradle Plugin 4.2.2.
Android SDK Build Tools 30.0.2 will be used.
To suppress this warning, remove "buildToolsVersion '28.0.3'" from your build.gradle file, as each version of the Android Gradle Plugin now has a default version of the build tools.
> Task :app:installDebug FAILED
Skipping device 'emulator-5554' (emulator-5554): Device is OFFLINE.
134 actionable tasks: 2 executed, 132 up-to-date
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:installDebug'.
> com.android.builder.testing.api.DeviceException: No online devices found.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 14s
error Failed to install the app. Make sure you have the Android development environment set up: https://reactnative.dev/docs/environment-setup.
Error: Command failed: ./gradlew app:installDebug -PreactNativeDevServerPort=8081
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:installDebug'.
> com.android.builder.testing.api.DeviceException: No online devices found.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 14s
at makeError (/Users/username/Appname/app/node_modules/@react-native-community/cli-platform-android/node_modules/execa/index.js:174:9)
at /Users/username/Appname/app/node_modules/@react-native-community/cli-platform-android/node_modules/execa/index.js:278:16
at processTicksAndRejections (internal/process/task_queues.js:95:5)
at async runOnAllDevices (/Users/username/Appname/app/node_modules/@react-native-community/cli-platform-android/build/commands/runAndroid/runOnAllDevices.js:94:5)
at async Command.handleAction (/Users/username/Appname/app/node_modules/@react-native-community/cli/build/index.js:186:9)
info Run CLI with --verbose flag for more details.
在我尝试集成Firebase和更新的android Studio之前，命令(react native run android(一直运行良好。
我试着做了几件事来解决这个问题，比如重新安装android studio或更新sdk工具。
当我运行(react native run android(时，JS服务器成功运行，android模拟器打开，但它没有下载应用程序
当我在终端中运行：adb设备时，我得到：
List of devices attached
emulator-5554 offline
我已经尝试过删除、冷重启、重新启动模拟器，但无济于事，而且总是显示脱机。
我真的很感激你的帮助。
提前感谢！
您可以尝试手动打开模拟器然后运行命令吗。。。如果它不起作用，就意味着它在你的代码中。。。或者，如果它不在你的代码中，你可以尝试检查其中一个答案。。。无法启动仿真程序。原因：Emulator在启动前退出en React Native当React Nation运行android 时
对不起，如果我不能帮忙。。。
请检查以下案例的
- 检查您是否在android工作室中安装了模拟器。安卓工作室>设置>系统设置>安卓SDK>选择SDK工具Android Emulator
- 在android的Build.Gradle中检查编译SDK版本。与安装的仿真程序版本匹配