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Android Eclipse only Generate the R file on Demand

Generating of R file works fine for me. But is there a way to get Eclipse to generate just the R file on demand.
Editing a layout file and re-ordering nextFocus attributes crashes the app, unless you regenerate the R file. So I have to clean the project to generate the R file. But my project is very large, and it feels like a waste of time to rebuild the whole project, just for one file. Is there a way/trick to generate just the R.file?
Note:
Build Automatically is checked.
I am working on Library Project, which contains most of the code base for free and paid versions of the app.

Let me reiterate what I understand from your question. Your project is huge and minor changes to a layout result in crashing - owing to rebuilding the entire project. So, you want to know how to build only a part of the project - with the R file instead of rebuilding the entire huge project on minor changes, which crashes.
What you can do is, uncheck the "Build automatically option", make your changes and build manually once all the changes have been made, instead of building the project on every saved change.
I don't think you can generate only the R file since it needs to read all the res files and generate ids for all the resources, excluding none...I don't think that can be done in parts.
There is a way to generate the R.java file from your resources using the Android Asset Packaging Tool (aapt) as stated here (thanks to Pearl for the pointer)

just click on project->buildautomatically to tick

You can't build R.java as per your requirement like it will not build whole project and generate only R.java file.
But let me tell you one thing, R.java file contains resources identifiers. Those identifiers will be generated if and only if project is build. So, you have to build project to stop crashing your project.
You can still unchecked Build Automatically and manually build project by Project -> Build Project option.

Android eclipse project is broken

After switching to my release branch the project had a missing gen file so I added the gen file from java build path.
Now the assets and the res folders are show like gray packages and not folders and I get the errors like res/values/ is missing.
How to return to the standard android project structure in eclipse?
Is there a standard way of returning to the standard Android project. I have become tired to fix project properties and I have tried to clean and restart eclipse It seams that some project metadata is saved the wrong way.
Thanks .

/gen/ folder is automatically generated during compilation. You should include that and /bin/ and also /.properties/ to .gitignore to avoid having to fix properties all the time and also minimise the amount of unnecessary data stored in your repo.

How to resolve the issue of android resources

i'm new to android, i'm getting this error. please help me in providing the solution
Thanks in advance.

R cannot be resolved to a variable When we will get this error.
R.java is an automatically generated file to hold all your resources used in project. It will be created under gen folder when you build your project. While building your project it will assign IDs to each resource you used in project and keeps them in their individual classes (drawable, id, layout, etc.) and creates a file R.java, place it in your package.
If anything wrong in your resource files (drawables or xml layouts) it won't generate R.java file.
So please check it once. I too faced same problem previously.

All the resources in Android are referenced by an 'id'. This 'id' is generated automatically in the file 'R.java', which itself is generated in automatically in 'gen' folder, once you build the project.
So, what you have to do is just 'Build your Project'

Build you project and you will get you.package.name.R.java file - and just import it.

I think I saw the problem. You are having 2 folders named 'res'.
Just delete the res folder which is empty and Clean, build the project

if your gen folder is still missing then check whether you have done installation properly and then check if you have any error on any of the xml files in your project
refer following links
R cannot be resolved - Android error
No generated R.java file in my project
No generated R.java file in my project
http://www.joshuakerr.com/2009/10/23/android-and-the-missing-gen-folder/

Should R.java be placed under version control

Is R.java file generated by Android SDK on each compile or only when new resources are added using Eclipse? Do I need to put it under version control or not?

The R.java file is generated during resource compilation by aapt tool. You shouldn't add it to source control system.
Also, you should have noted the gen folder where R.java is placed. Your version control system should ignore this folder altogether, not only R.java file inside it. Because this folder is deleted on clean build (not sure about eclipse, but ant script definitely deletes it).

When using Git to control Android projects I add
bin/*
gen/
to .gitignore

You don't need to put it under version control. I think it's on each compile, one every new resource or clean up project.. but need to test to be sure.

I have had projects with R in and out of source control. Both worked.

When the android SDK is loaded into eclipse, it will automatically generate the R.java file. In older versions of the adt, having an incorrect R.java file would give an error, but I believe this is fixed now, and it shouldn't matter either way. If you have the choice though, avoid checking it in.
I would add it to svn:ignore.

Cannot create R.java b/c project has errors...errors result from lack of R.java

edit: This is an Android project. My problem arose when I added a new .wav file to my 'raw' folder.
I seem to have gotten into an endless loop in Eclipse. I deleted my R.java file from my project. Choosing to "Clean" or "Build Project" has no effect (i.e. doesn't generate an R.java file, or put anything into the 'gen' folder, or create any .class files in the 'assets' folder).
I don't have the wrong package name in any of my classes or in my manifest.
I don't have any errors in any of my .xml files.
Every reference to 'R' in my classes are marked as errors, because the R.java file does not exist.
What can I do??

Try deleting the wav file first. If it doesn't fix your problem, look under problems tab and it will give you a direction on what to do. A wav file under res/ shouldn't produce any problems, just make sure its name is valid in Java (don't use -, for example).

I solved this problem creating a blank project and copying the folder "gen" from this project to others projects. After that I rebuilt all projects and Eclipse automatically replaced the R.java file.

if you rebuild it is there any error message on the console? or are you using capital letters or other special characters in your wav file?

Another issue I noticed, it seems that after closing and re-opening eclipse with a slightly invalid XML file, the XML was no longer recognised as having an error, but R.java refused to be generated correctly.
The offending XML attribute was:
<RelativeLayout ...
android:layout_alignRight="+id/">
In hindsight, I had been intending to complete this with a valid id but I exited the program before I had finished. Eclipse did not pick up the error when I restarted later, except to generate an invalid R.java with a missing VariableDeclaratorId (and no indication as to what caused it).