React-Native Build Failed app:mergeDebugAssets

Try running this inside your project directory:

1. cd android
2. gradlew clean
3. cd..
4. react-native run-android

I had this issue and for me ./gradlew clean didn't help.

But I found a file called assets in android/app/src/main that git showed as untracked. When I removed the assets file I could build the project without problems again.

I use Android Studio for debugging java code and I would guess that is why the assets file was created.