How to create a library project in Android Studio and an application project that uses the library project

I'm new to the gradle build system and IntelliJ.

So how do I create an Android Library Project (e.g. com.myapp.lib1) and the application project (e.g. com.myapp.app) and make the build system include com.myapp.lib1 on the application project?

I went to the Project Structure -> Modules -> My App project and added a dependency to the lib project. IntelliJ now can recognize classes from the lib project when used in the app project, but when I run the app project, there are errors like:

Gradle: error: package com.myapp.lib1 does not exist

Solution 1:

I wonder why there is no example of stand alone jar project.

In eclipse, we just check "Is Library" box in project setting dialog.
In Android studio, I followed this steps and got a jar file.

1. Create a project.

2. open file in the left project menu.(app/build.gradle): Gradle Scripts > build.gradle(Module: XXX)

3. change one line: apply plugin: 'com.android.application' -> 'apply plugin: com.android.library'

4. remove applicationId in the file: applicationId "com.mycompany.testproject"

5. build project: Build > Rebuild Project

6. then you can get aar file: app > build > outputs > aar folder

7. change aar file extension name into zip

8. unzip, and you can see classes.jar in the folder. rename and use it!

Anyway, I don't know why google makes jar creation so troublesome in android studio.

Solution 2:

To create a library:

File > New Module

select Android Library

To use the library add it as a dependancy:

File > Project Structure > Modules > Dependencies

Then add the module (android library) as a module dependency.

Run your project. It will work.