Change package name for Android in React Native?

Answer

I've renamed the project' subfolder from: "android/app/src/main/java/MY/APP/OLD_ID/" to: "android/app/src/main/java/MY/APP/NEW_ID/"

Then manually switched the old and new package ids:

In: android/app/src/main/java/MY/APP/NEW_ID/MainActivity.java:

package MY.APP.NEW_ID;
In android/app/src/main/java/MY/APP/NEW_ID/MainApplication.java:

package MY.APP.NEW_ID;
In android/app/src/main/AndroidManifest.xml:

package="MY.APP.NEW_ID"
And in android/app/build.gradle:

applicationId "MY.APP.NEW_ID"
In android/app/BUCK:
android_build_config(
package="MY.APP.NEW_ID"
)
android_resource(
package="MY.APP.NEW_ID"
)
Gradle' cleaning in the end (in /android folder):

./gradlew clean