In past year some of Android beginners have some problem to add external library in Android Studio. Well most of you know that you can add it on gradle and sync the project. But here i am telling you three approaches by which you can easily add external library in android studio.
I personally recommended third approach but you can use any of them which you think easy.
Try one of these approaches:
1- Choose project view
2- Copy your JAR file in app -> lib folder
3- Right click on your JAR file and choose add as library
4- Check it in build.gradle
1- File -> New -> New Module
2- Import .JAR/.AAR Package
3- Browse your JAR File
5- File -> Project Structure -> Dependencies
6- You should click on + button and then click on Module Dependency
7- You will see your library here
8- choose your library and click ok
9- Then, you will see that your library is added.
For first two approaches, you need a JAR file. You can search http://search.maven.org/ to find JAR files that are related to Android. For example, this is the search result for jdom in this link
Android is using http://jcenter.bintray.com/ as remote library. For example, this is the search result for jdom in the link.
To add a library in this approach, please follow these steps:
1- File -> Project Structure -> Dependencies
2- Click on + button and choose library dependency
3- find your library and select it, then click OK.
I hope it helps.