how to create library ( jar ) in android studio ?

Question

I want to create some library that i will use in the future beside my current project.

I can't find a way to create library in android studio.

How to do it on android ?

Answer 1

As introduction I would suggest you to peek into this conceptually simple tutorial. Basically you can start your own library module when you chose your project, without adding any Activity. Then you create your Java Class, usually with a View. When your library is ready, with all its business logic, you can glue everything inserting in the top level build gradle the instruction you are using a library, basically before you remove the following line, that is not needed for a library:

applicationId

(This line in your gradle file is a unique application ID that looks like a Java package name, that identifies your app to the device you are running and in google play)

and then you change this line:

apply plugin: 'com.android.application'

to:

apply plugin: 'com.android.name_library'

When you have a more structured project you can follow the official documentation As it is well explained the difference between a normal Application and a Library is:

An Android library is structurally the same as an Android app module. It can include everything needed to build an app, including source code, resource files, and an Android manifest. However, instead of compiling into an APK that runs on a device, an Android library compiles into an Android Archive (AAR) file that you can use as a dependency for an Android app module.

I would not encourage you to use solutions like web services that do it on your behalf, namely just copying/pasting your existing code. In fact a library often needs specific architectural choices, so is important to consider and learn different factors, is not just writing some business logic is quite complex to explain, but you can imagine that also the choice of what the user can see and modify can be crucial. Also should be as much as possible bug free, because once it is adopted could cause problems to the users. I remand you to a famous post, superbly written where you can find some solution to this aspect.

Answer 2

A library module is useful in the following situations: When you're building multiple apps that use some of the same components, such as activities, services, or UI layouts. When you're building an app that exists in multiple APK variations, such as a free and paid version and you need the same core components in both. In either case, simply move the files you want to reuse into a library module then add the library as a dependency for each app module. To create a new library module in your project, proceed as follows:

Click File > New > New Module.

In the Create New Module window that appears, click Android Library, then click Next.

There's also an option to create a Java Library, which builds a traditional JAR file.

Give your library a name and select a minimum SDK version for the code in the library, then click Finish.

Once the Gradle project sync completes, the library module appears in the Project panel on the left.

If you don't see the new module folder, make sure it's displaying the Android view.

Visit https://developer.android.com/studio/projects/android-library.html

Answer 3

you can use https://jitpack.io/ is very easy publish an android library. just upload your code to github/bitbucket and paste the repository link on jitpack website. that's all