Import an Android Library Project in Android Studio

Posted on Sunday January 04, 2015 / by Eric Potvin

Common libraries are essential in development. They are very useful and can avoid hours of unwanted development. In a previous article, I talked about how to create an android library project and why you should create one for your projects.

In this article, I will talk about how to import and use this library in your Android Application Project.

First, let's create a basic application.

Create an application

Start Android Studio and choose Start a new Android Studio project.

Now let's use as Application name: HelloJar and the Company Domain: appdemo.

Click Next

Select Phone and Tablet and choose your API level (I use API 15).

Click Next

Select Blank Activity

Click Next

You can customize the Blank Activity settings if you want. For this demo, we will use the default values.

Click Finish

The main layout will (or should be) open and you will see the "Hello world!" text in the preview emulator.

Updating the code!

Let's change this to display: Hello Book of Zeus.

1) Importing the library

First we need to import the .JAR file by copying the library in the libs folder. Make sure you are in the Project view mode (Top left corver of the Project window).

2) Adding as library

Right click on the .JAR file and select the last option Add as library.

3) Gradle update

Gradle should add the library automatically. But just in case open the build.gralde (Module: app) and look under dependencies. You should see something like this:

compile files('libs/MyLibrary.jar')

4) Clean the project

Now that the library is added, clean the project (Build -> Clean Project). You should see BUILD SUCCESSFUL in the gradle console.

Using the library

To change the text of the TextView object, we will need to make sure the main class (in my case MainActivity) access the TextView.

First, we will need to create an ID to the TextView:

<TextView
	android:id="@+id/txt_hello"
	android:text="@string/hello_world"
	android:layout_width="wrap_content"
	android:layout_height="wrap_content" />

Let's modify the "Hello world!" to show, Hello %s! instead!

Open the strings.xml and update the hello_world value to:

<string name="hello_world">Hello %s!</string>

Then, in the .java file let's use it.

TextView mHello = (TextView)findViewById(R.id.txt_hello);

Let's now use the library object. Remember the structure of the LibraryDemo class?

LibraryDemo lib = new LibraryDemo();
CharSequence name = (CharSequence)lib.getSiteName();

And set the text to the TextView:

mHello.setText(String.format(getString(R.string.hello_world), name));

Make sure you import the import com.mylibrary.LibraryDemo; before compiling the application.

Clean and run the project!

Download this project at https://github.com/BookOfZeus/HelloJar