Android app project in eclipse has many package errors, how do I fix this?

Question

I was working on an app about a year ago, and kinda forgot about it for some time. I want to get back into it, but every import has an error. I feel like I am just forgetting something simple, but I dont know what it is.

standard java projects (non-android) work fine, but anything android related has errors. I tried updating to the newest sdk (23.0.2), but that did not fix the problems.

here is a screenshot of what is going on.

Edit: I also just insalled the newest build tools, and all the extras in the android sdk manager. This did not fix the problem.

edit 2: It seems that if I go to the Library build paths, the JRE System Library can't be added. If I added, the name of it changes to "Unable to get system library for this project" This only happens with android projects, and not with non-android projects.

Final edit: the problem was fixed by changing the android target version

Answer 1

The following steps could help:

Right-click on project » Properties » Java Build Path
Select Libraries tab
Find the JRE System Library and remove it
Click Add Library... button at right side » Add the JRE System Library (Workspace default JRE)

After this clean your project.