
Go to your project directory and check if this folder assets exists in project directory, if not then create the new folder assets.
android/app/src/main/assets
Run the command ./gradlew clean from the android folder.
cd android
.\gradlew clean
Note :In some operating system ./gradlew clean is used instead of .\gradlew clean
Finally, navigate back to the root directory and check.
1.If there is only one file i.e. index.js then run following command.
react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res
2.If there are two files i.e index.android.js and index.ios.js then run this
react-native bundle --platform android --dev false --entry-file index.android.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res
Now run the command react-native run-android