无法在 android 上运行 react-native

Question

How to fix this error on running react-native on android

Failed to construct transformer:  DuplicateError: Duplicated files or mocks. Please check the console for more info
at setModule (/home/user/HelloWorld/node_modules/jest-haste-map/build/index.js:620:17)
at workerReply (/home/user/HelloWorld/node_modules/jest-haste-map/build/index.js:691:9)
at runMicrotasks (<anonymous>)
at processTicksAndRejections (internal/process/task_queues.js:93:5)
at async Promise.all (index 16960) {
   mockPath1: 'node_modules/react-native/template/package.json',
   mockPath2: 'package.json'
}

Answer 1

This could happen when there are some changes that got cached in build. remove android build folder by running

rm -rf android/build

then after closing Metro bundler terminal. run the app again by react-native run-android .

If the same is happening for ios remove ios/build and ios/Pods and re install Pod.

Answer 2

This could happen if you have multiple checkouts of your react-native project. Maybe one inside another. This could result in detecting multiple package.json files. Delete the duplicate checkout. Clean and Build.