Android Studio: Add jar as library?

I've been struggling with the same thing for many hours, trying to get the Gson jar to work no less. I finally cracked it – here are the steps I took:

1. Put the Gson jar (in my case, gson-2.2.4.jar) into the libs folder
2. Right click it and hit 'Add as library'

3. Ensure that compile files('libs/gson-2.2.4.jar') is in your build.gradle file (or compile fileTree(dir: 'libs', include: '*.jar') if you are using many jar files)

   Edit : Use implementation files('libs/gson-2.2.4.jar') (or implementation fileTree(dir: 'libs', include: '*.jar')) in Android Studio 3.0+

4. Do a clean build (you can probably do this fine in Android Studio, but to make sure I navigated in a terminal to the root folder of my app and typed gradlew clean. I'm on Mac OS X, the command might be different on your system

After I did the above four, it started working fine. I think the 'Add as library' step was the one I'd previously missed, and it didn't work until I cleaned it either.

[Edit - added the build.gradle step which is also necessary as others have pointed out]

Here are the instructions for adding a local jar file as a library to a module:

1. Create a 'libs' folder in the top level of the module directory (the same directory that contains the 'src' directory)

   

2. In the build.gradle file add the following so that your dependencies closure has:

   dependencies {
       // ... other dependencies
       compile files('libs/<your jar's name here>')
   }
   

3. Android Studio should have already setup a gradlew wrapper. From the command line, navigate to the top level of your project (the directory that has a gradlew file).

   Run ./gradlew assemble. This should compile the project with the library. You may need to fix errors in your build.gradle file as necessary.

4. In order to have Android Studio recognize the local jar files as libraries for support while coding in the IDE, you need to take a few more steps:

   4.1. Right click on the module in the left hand panel and choose Open Library Settings.

   

   4.2. On the left panel of the dialog, choose Libraries.

   4.3. Click the + sign above the panel second from the left -> Java

   

   4.4. Select your local jar and add it to the project.

5. You may need to run the above ./gradlew command one more time