Home » Android » android – deleted gen folder, eclipse isn't generating it now :(

android – deleted gen folder, eclipse isn't generating it now :(

Posted by: admin June 15, 2020 Leave a comment


I accidentally deleted my gen folder and now, predictably, my resources are all messed up. I just created a gen folder myself and tried to project > clean – that didn’t work. Tried right-clicking project and going to android tools > fix project properties – didn’t work. Tried unchecking build automatically…didn’t work. cleaned, closed project, closed eclipse, restarted, etc, etc. Nothing is working and I keep seeing this error: gen already exists but is not a source folder. Convert to a source folder or rename it.

EDIT – OK was able to generate R.java, but now I’m getting crazy stuff in the console:

[2011-06-14 17:06:11 – fastapp] Conversion to Dalvik format failed
with error 1
[2011-06-14 17:06:42 – fastapp] Dx
trouble processing “java/awt/font/NumericShaper.class”:

Ill-advised or mistaken usage of a core class (java.* or javax.*)
when not building a core library.

This is often due to inadvertently including a core library file
in your application's project, when using an IDE (such as
Eclipse). If you are sure you're not intentionally defining a
core class, then this is the most likely explanation of what's
going on.

However, you might actually be trying to define a class in a core
namespace, the source of which you may have taken, for example,
from a non-Android virtual machine project. This will most
assuredly not work. At a minimum, it jeopardizes the
compatibility of your app with future versions of the platform.
It is also often of questionable legality.

If you really intend to build a core library -- which is only
appropriate as part of creating a full virtual machine
distribution, as opposed to compiling an application -- then use
the "--core-library" option to suppress this error message.

If you go ahead and use "--core-library" but are in fact
building an application, then be forewarned that your application
will still fail to build or run, at some point. Please be
prepared for angry customers who find, for example, that your
application ceases to function once they upgrade their operating
system. You will be to blame for this problem.

If you are legitimately using some code that happens to be in a
core package, then the easiest safe alternative you have is to
repackage that code. That is, move the classes in question into
your own package namespace. This means that they will never be in
conflict with core system classes. JarJar is a tool that may help
you in this endeavor. If you find that you cannot do this, then
that is an indication that the path you are on will ultimately
lead to pain, suffering, grief, and lamentation.

[2011-06-14 17:06:42 - fastapp] Dx 1 error; aborting
[2011-06-14 17:06:42 - fastapp] Conversion to Dalvik format failed with error 1

And eclipse can’t resolve the import of my resources import

How to&Answers:
  1. Right click your project
  2. Select properties.
  3. Select Java Build Path
  4. Click add Folder
  5. Select the gen folder
  6. Click OK.


I don’t know if this qualifies as an answer, but I eventually threw my hands up and just reverted to my last commit.


I had the same issue today after upgrading my SDK to v22 and ADT to the newer version. Apparently my SDK Manager didn’t detect there were also changes to the SDK Platform-Tools and the newly introduced SDK Build-tools so it didn’t upgrade tools, causing my SDK/ADT bundle to not generate contents of the /gen folder within Eclipse.

I had to go back to the SDK Manager after upgrading both SDK and ADT so it would offer me the options to install/update SDK Platform-tools to 17 (from 16 I had) and SDK Build-tools (also 17).


There is probably a problem with the preparation of the R class (for instance, because of error in some layout xml). Turn the builder output to “verbose” from Preferences and see in the console where the generation breaks.