Overriding a Class from Android Library Project

Question

I make sereval Android apps with similar code, but I need to stay flexible for customizing the apps. My solution right now is, that I have a Library-Project, where I can override functionality in the Project by extending classes. For the following example, I call the Library Project PL. P1 is a customized Project using PL and P2 is another customized Project using PL.

My Problem is now, that in PL I would like to make an instance from StudentPL.java. In P1, there is no need to make any changes to StudentPL, so the compiler should take this class, but in P2, there I have StudentP2.java, that extends from StudentPL.java. So the instance made in PL, should be an instance of StudentP2.java.

My idea was now, that I make a package called mirror, that is directly in the src-Folder of the Project PL. There I make the class mirror.Student.java that extends from StudentPL.java. In the Library-Project, I make now an instance of Student.java. For Project P1, there are no changes needed. In P2 I make the same folder mirror in src Folder and I make the same class mirror.Student.java that extends from StudentP2.java now. The Idea is, that the ClassLoader now loads mirror.Student.java from P2 and ignores mirror.Student.java from PL, but this results in the following error:

• Dex Loader] Unable to execute dex: Multiple dex files define Lmirror/Student;
• Conversion to Dalvik format failed: Unable to execute dex: Multiple dex files define Lmirror/Student

Here is a UML of what I'm talking about:

http://www.koenix-band.ch/images/other/Stackoverflow.gif

Maybe I should overwrite the ClassLoader, but I have no idea how to do this? Does anyone have an idea to solve this problem? Maybe someone has another idea, how i could customize the apps.

Michael

Answer 1

In my opinion it would be better to make your MainActivityPL abstract with a setStudent or similar method. The bulk of the activity and all its logic would still be shared from your library, but it would allow your other projects an option to use different student objects by extending the StudentPL class.