Android Studio: Add jar as library?

Question

I'm trying to use the new Android Studio but I can't seem to get it working correctly.

I'm using the Gson library to serialize/deserialize JSON-objects. But the library somehow isn't included in the build.

I had created a new project with just a MainActivity. Copied gson-2.2.3.jar in the /libs folder and added it as a library dependancy(right click->Add as library). This includes the jar in android studio so it can be referenced from the source files.

When I try to run the project it cannot compile so I added:

compile files('libs/gson-2.2.3.jar')

to the dependencies in de .gradle file. After that it compiles correctly but when running the application I get a ClassDefNotFoundException.

Does anyone know what I'm doing wrong?

Answer 1

1. Put the jar (in my case, gson-2.2.4.jar) into the libs folder.

2. Ensure that compile files (libs/gson-2.2.4.jar) is in your build.gradle file.

3. Now Click on the "Sync Project with Gradle files"(Left to AVD manager Button on the topbar).

After I did the above three, it started working fine.

Answer 2

Put the .jar files in libs folder of the Android project.

Then add this line of code in the app's gradle file:

    compile fileTree(dir: 'libs', include: ['*.jar'])

For Android gradle plugin 3.0 and later, it is better to use this instead:

    implementation fileTree(dir: 'libs', include: ['*.jar'])

Answer 3

Unlike Eclipse we don't need to download jar and put it in /libs folder. Gradle handles these things we only need to add Gradle dependencies, Gradle downloads it and puts in gradle cache.

We need to add dependencies as:

dependencies {implementation 'com.google.code.gson:gson:2.2.4'}

thats it However we can also download jar & add that as library but the best practice is to add Gradle dependencies.

Answer 4

menu File -> project struct -> module select "app" -> dependencies tab -> + button 
-> File dependency -> PATH/myfile.jar

Answer 5

Like many before pointed out you shall add

compile files('libs/gson-2.2.3.jar') 

to your build.gradle file.

However I have a project in Android Studio that was migrated from Eclipse and in this case the "libs" folder is named "lib" so for me removing the "s" solved the problem.

Answer 6

Step 1 : Now under your app folder you should see libs, if you don't see it, then create it .

Step 2 : Drag & Drop the .jar file here, you may be get a prompt "This file does not belong to the project", just click OK Button .

Step 3 : Now you should see the jar file under libs folder, right click on the jar file and select "Add as library", Click OK for prompt "Create Library"

Step 4 : Now this jar has been added.