I created and built my android project successfully. I close the Eclipse and reopen it and have lots of errors. I clean and refresh and rebuild my project but the error is not disappeared.
I open project properties (Alt+Enter), change the project build target to any other API and apply it and again I select my previous API and click OK.
Now everything is OK and my project is built successfully.
Why? Why the build target is not selected after opening the Eclipse and I have to reselect it?
How can I solve it permanently?
I think you should check your "AndroidManifest.xml".
Edit:
You should check if SDK versions
<uses-sdk android:minSdkVersion="19" android:targetSdkVersion="19" />
are in the existing installed APIs.