如何在Android Studio模拟器中打开React Native应用？遇Gradle空指针错误

错误信息 #

执行npx react-native run-android后模拟器成功启动，但应用安装失败，报错如下：

$ npx react-native run-android

info JS server already running.
info Launching emulator...
info Successfully launched emulator.
info Installing the app...
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.lastIndexOf(String)" because "path" is null
        at org.gradle.wrapper.PathAssembler.getDistName(PathAssembler.java:83)
        at org.gradle.wrapper.PathAssembler.getDistribution(PathAssembler.java:39)
        at org.gradle.wrapper.Install.createDist(Install.java:58)
        at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:107)
        at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:63)

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.bat app:installDebug -PreactNativeDevServerPort=8081
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.lastIndexOf(String)" because "path" is null
        at org.gradle.wrapper.PathAssembler.getDistName(PathAssembler.java:83)
        at org.gradle.wrapper.PathAssembler.getDistribution(PathAssembler.java:39)
        at org.gradle.wrapper.Install.createDist(Install.java:58)
        at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:107)
        at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:63)

    at makeError (E:\Code Projects\AwesomeProject\node_modules\@react-native-community\cli-platform-android\node_modules\execa\index.js:174:9)
    at E:\Code Projects\AwesomeProject\node_modules\@react-native-community\cli-platform-android\node_modules\execa\index.js:278:16
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async runOnAllDevices (E:\Code Projects\AwesomeProject\node_modules\@react-native-community\cli-platform-android\build\commands\runAndroid\runOnAllDevices.js:109:5)
    at async Command.handleAction (E:\Code Projects\AwesomeProject\node_modules\@react-native-community\cli\build\index.js:142:9)
info Run CLI with --verbose flag for more details.

解决方案 #

1. 检查Gradle Wrapper配置文件 #

• 进入项目的android/gradle/wrapper目录，打开gradle-wrapper.properties文件
• 确保distributionUrl字段不为空，且格式正确，示例：

  distributionUrl=https\://services.gradle.org/distributions/gradle-7.5-all.zip
  

  （注意：Gradle版本需与项目React Native版本兼容，可参考根目录package.json中react-native版本对应的官方要求）
• 若字段为空或格式错误，修改为有效URL后保存文件

2. 清理Gradle缓存 #

• 删除本地Gradle缓存文件夹：
  • Windows：C:\Users\<你的用户名>\.gradle\wrapper\dists
  • Mac/Linux：~/.gradle/wrapper/dists
• 进入项目的android目录，执行命令：

  # Windows
  gradlew clean
  # Mac/Linux
  ./gradlew clean
  

• 重新执行npx react-native run-android

3. 验证环境变量配置 #

• 确认ANDROID_HOME（或ANDROID_SDK_ROOT）已正确设置为Android SDK安装目录
• 确认JAVA_HOME指向JDK 11的安装目录（React Native官方推荐版本）
• 重启命令行终端，确保环境变量生效后再尝试运行应用

4. 重新生成Gradle Wrapper #

若上述步骤无效，可手动重新生成Wrapper：

• 进入项目的android目录，执行命令（替换为对应版本号）：

  gradle wrapper --gradle-version 7.5
  

• 生成完成后，再次执行npx react-native run-android

内容的提问来源于stack exchange，提问作者Chaman Narved