Cant run React Native Project on Emulator anymore

Question

for some reason my App wont start up on my AS Emulator. Yesterday everything was working great but today it doenst work - might be because I moved npm and npm-cache folder but they are set correctly with npm config.

Metro server starts OK and if I just selected the app it would load it up but now it insta crashes..

If I try to run npm android I am getting the error below:

    PS C:\Dev\Programmierung\FitnessApp\FitnessApp> npm run android

> FitnessApp@0.0.1 android C:\Dev\Programmierung\FitnessApp\FitnessApp
> react-native run-android

info Running jetifier to migrate libraries to AndroidX. You can disable it using "--no-jetifier" flag.
Jetifier found 1158 file(s) to forward-jetify. Using 6 workers...
info Starting JS server...
Der Befehl "adb" ist entweder falsch geschrieben oder
konnte nicht gefunden werden.
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:transformClassesWithDexBuilderForDebug FAILED

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.0.1/userguide/command_line_interface.html#sec:command_line_warnings
147 actionable tasks: 3 executed, 144 up-to-date

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:transformClassesWithDexBuilderForDebug'.
> Unable to delete directory 'C:\Dev\Programmierung\FitnessApp\FitnessApp\android\app\build\intermediates\transforms\dexBuilder\debug\0\androidx\appcompat' after 10 attempts

* 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 17s

error Failed to install the app. Make sure you have the Android development environment set up: https://reactnative.dev/docs/getting-started.html#android-development-environment. Run CLI with --verbose flag for more details.
Error: Command failed: gradlew.bat app:installDebug -PreactNativeDevServerPort=8081

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:transformClassesWithDexBuilderForDebug'.
> Unable to delete directory 'C:\Dev\Programmierung\FitnessApp\FitnessApp\android\app\build\intermediates\transforms\dexBuilder\debug\0\androidx\appcompat' after 10 attempts

* 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 17s

    at makeError (C:\Dev\Programmierung\FitnessApp\FitnessApp\node_modules\execa\index.js:174:9)
    at C:\Dev\Programmierung\FitnessApp\FitnessApp\node_modules\execa\index.js:278:16
    at processTicksAndRejections (internal/process/task_queues.js:94:5)
    at async runOnAllDevices (C:\Dev\Programmierung\FitnessApp\FitnessApp\node_modules\@react-native-community\cli-platform-android\build\commands\runAndroid\runOnAllDevices.js:94:5)
    at async Command.handleAction (C:\Dev\Programmierung\FitnessApp\FitnessApp\node_modules\react-native\node_modules\@react-native-community\cli\build\index.js:186:9)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! FitnessApp@0.0.1 android: `react-native run-android`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the FitnessApp@0.0.1 android script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Dev\npm\npm-cache\_logs\2020-04-24T08_01_58_811Z-debug.log

Answer 1

The fixx for me was to:

cd android

./gradlew clean

and rebuild app twice