Why do errors no longer appear in Eclipse's package explorer?

Question

My project used to be fine - errors showed up in the file margin, the editor breadcrumb, the problems view and in the package explorer tree as little red X marks.

Somewh

Answer 1

Yet another reason for this type of problem: you might not be viewing your project with the correct perspective selected. I recently had this problem with 4 projects in my workspace, 3 of which were PyDev projects and the other was an Android project. In my case, only the Package Explorer was misbehaving, not showing up warnings or errors, but the Problems view and the files themselves were showing the errors and warnings.

It turned out that the PyDev perspective was active even while I had the Android project selected. To change perspective, go to Window -> Open Perspective --> [Perspective Name] or alternatively hit the Perspective shortcut button in the top-right corner of Eclipse.

This is relevant to Eclipse Indigo, I can't speak for other versions.