How to create your own library for Android development to be used in every program you write?

Question

I am a Delphi programmer and have written, over the years, hundreds of classes and routines which I can use in every Delphi program I write.

This library is called dlib and can be used in every Delphi program by putting this folder in my library path and using one of the units in the uses section of a Delphi unit.

Being completely new to Java and Android development, I am wondering how to do this in similar way.

So my question, how can I write own classes, put them in some global folder, and use these classes and routines in every Android program I write ?

I know this is a basic question, which I can probably find out by searching Google and trying it out in Eclipse, but if someone can put me on the right track, I know I will save much time.

Thanks.

Answer 1

You have to create Android Library Project. Create android project in Eclipse, enter Project Properties -> Android and check isLibrary property. Now you can add this library to your Android Application project by adding it to list on the same property page.

More detailed instructions here in Working with Library Projects section

Answer 2

Instructions for creating a library in Android Studio:

Create a library module

To create a new library module in your project, proceed as follows:

1. Click File > New > New Module.

2. 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. While a JAR file is useful for many projects—especially when you want to share code with other platforms—it does not allow you to include Android resources or manifest files, which is very useful for code reuse in Android projects. So this guide focuses on creating Android libraries.

3. 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.

Convert an app module to a library module

If you have an existing app module with all the code you want to reuse, you can turn it into a library module as follows:

1. Open the module-level build.gradle file.

2. Delete the line for the applicationId. Only an Android app module can define this.

3. At the top of the file, you should see the following:
   
   apply plugin: 'com.android.application'
   
   Change it to the following:
   
   apply plugin: 'com.android.library'
   
   Save the file and click Tools > Android > Sync Project with Gradle Files.