'R cannot be resolved to a variable' - gen folder is empty

Question

I've got an error:

R cannot be resolved to a variable

in line:

setContentView(R.layout.main);

but I can't resolve it doing things that other users wrote should be tried, which are:

Getting rid of 'import android.R' line.
Cleaning the project and then building it again.
Closing project and then opening it again.
Going to Project Properties > Java Build Path > Tick Android Version Checkbox
Following the procedure: Uncheck Project->Build Automatically Project->Properties->Builders: Make sure all Android (3) and Java (1) builders are checked (and nothing more) Window->Preferences->Android->Build: Check "Automatically refresh Resources and Assets folder on build" Right-click on project->Android Tools->Fix Project Settings (not sure what it actually does, but it can't hurt)
Some users advice to check if .xml files are correct. I don't know how I could do that. I must admit I'm new to java and android programming, and I haven't even written a single line in my project - the code has been generated automaticly.
Layout xml file is named using lower-case letters.
No error in resource files (no red-crosses).

layout main.xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

</LinearLayout>

Thanks in advance for your help!

check in your XML files in that might be you uses resource that is not available in your resources.because it some time not show you error but when you clean and build the project is not built successfully. — Hiren Dabhi
– Hiren Dabhi, Commented Feb 16, 2012 at 13:46
2 Downvotes? Seriously? Did you only read the title of the question? He clearly did a lot of research and checked things beforehand. This question is clear and has enough details for starters. Everything mentioned in the thread linked in the comments is already done. And all the lazy questions with ZERO reseach effort get upvoted to the sky. I don't get you at times, SO community. — user658042
– user658042, Commented Feb 16, 2012 at 14:09
@Deepak Not an exact duplicate. Also,at least please read the WHOLE question before downvoting it(anyone). — Fofole
– Fofole, Commented Feb 16, 2012 at 14:15
I'm just going crazy as I'm trying to figure it out for two days now. It's hard to mention ALL things I've already tried... I've seen the above-mantioned post. I've pointed out the most common resolutions. — Quarra
– Quarra, Commented Feb 16, 2012 at 14:18
Is this problem only in your current project or also in new created projects too ? Try to recreate your project and check this and please notify me if this problem get solved or not. — Deepak
– Deepak, Commented Feb 16, 2012 at 16:29

Blackbelt · Accepted Answer · 2014-02-21 14:40:24Z

5

Check your res/ folder in order to be sure that every file it contains has no error. If any error exists R can not be generated.

edited Feb 21, 2014 at 14:40

answered Feb 16, 2012 at 14:18

Blackbelt

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12 Comments

Quarra Over a year ago

Is it possible that no red-cross occurs if a file contains an error? Maybe there is a problem with res folder, but I can't see it for some reason?

Blackbelt Over a year ago

dunno it is possible or not but remember that R.java is automatically generating from the res folder content (R.java contains your layout id, for instance). So, my best guess is the problem is there.

Quarra Over a year ago

main.xml file looks like that: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> </LinearLayout> Sorry, I don't know why it isn't displayed properly..

Blackbelt Over a year ago

";" a part it seems correct to me. Anything inside the drawable or values folder?

Quarra Over a year ago

Yes, in drawable-hdpi, drawable-ldpi, drawable-mdpi there are images of the Android (named ic_launcher.png). Folder values contains strings.xml

|

showlove · Accepted Answer · 2013-02-18 21:40:57Z

1

Yeah, i got stuck on this for hours. My solution was to: delete all projects from workspace->re-import the desired project by going to file->import->Browse->selecting the project->and finally check the "add project to working sets box" then clicking finish. The .R errors i once had then disappeared. I hope this helps someone!

answered Feb 18, 2013 at 21:40

showlove

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Comments

edthethird · Accepted Answer · 2012-02-17 05:02:41Z

1

Don't import Android.R;

instead,

import package.name.R; where package.name is your package name declared in the manifest.

Android.R contains all the default layouts packaged with Android. Your custom layout will not be Android.R, it will be in package.name.R;

answered Feb 17, 2012 at 5:02

edthethird

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2 Comments

Quarra Over a year ago

I tried this also. I've got another error in addition to the first one: The import my.second.project.R cannot be resolved I suppose it's not a solution.

edthethird Over a year ago

if R isn't being generated, there is a problem with one of your resources. Check out your layouts and drawables and manifest, make sure nothing is marked red. Once R is generated, you want to make sure you are referencing my.projet.R instead of Android.R

Fofole · Accepted Answer · 2012-02-16 13:42:10Z

0

On eclipse you have the "Problems" window. If you fix all the other problems in there other than R cannot be resolved, the "R" problem will be auto-fixed as R is not generated because most likely you have project related problems.

Hope this helps. If you don't manage to do it, put a print of what your Problems window is showing.

answered Feb 16, 2012 at 13:42

Fofole

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3 Comments

Quarra Over a year ago

I can't upload an image (insufficient raputation points). I've got one and only problem in 'Problems' window: {R cannot be resolved to a variable main.java}

Fofole Over a year ago

Try go to main.java press ctrl+shift+O and import the right R. Dunno if this works but worth trying.

Quarra Over a year ago

Well, I'm not an expert, but other users don't recommend it as it generates import android.R which isn't the issue here.

Vikram Singh · Accepted Answer · 2012-02-16 13:42:42Z

0

Clean your project once. It should build that file again automatically. Go to Project->Clean Of course, it will work ony if your xml files are syntactically correct!

answered Feb 16, 2012 at 13:42

Vikram Singh

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Fofole Over a year ago

It would be nice reading the actual question in which he states he cleaned the project.

Nitin Bansal · Accepted Answer · 2012-02-16 13:47:24Z

0

Delete your R.java fie and let it generate again...possibly this will help...i had same issue multiple times

answered Feb 16, 2012 at 13:47

Nitin Bansal

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Quarra Over a year ago

I didn't have a R.java file in the first place.

AndroDev · Accepted Answer · 2012-02-16 13:47:28Z

0

Try this: comment setContentView(R.layout.main); and the build/clean your project again. Then uncomment the commented line. This issue should not be seen then.

answered Feb 16, 2012 at 13:47

AndroDev

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Quarra Over a year ago

Tried this one. No effect - still the same problem.

AndroDev · Accepted Answer · 2012-02-17 04:54:21Z

0

Try this:

First disable automatic build option from Project>Build Automatically
Change eclipse work space
Create a new Hello World test project
Comment setContentView(R.layout.main);
Build project manually by right click on your project in eclipse>Build project
Check whether R.java in gen folder has been generated
If yes, then uncomment setContentView(R.layout.main);
Now build project again manually and run

This should resolve the problem hopefully.

answered Feb 17, 2012 at 4:54

AndroDev

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2 Comments

Quarra Over a year ago

I've tried it. R.java hasn't been generated, therefore the error hasn't disapired.

AndroDev Over a year ago

Did you download Android SDK properly? Just check whether aapt.exe is available in android_sdk/plateform tools folder.

Quarra · Accepted Answer · 2012-02-17 13:42:38Z

0

Problem is solved, but I don't know what has changed... I reinstalled Eclipse, SDK etc. and gen folder was empty as before, the same problem.

My supervisor told me to do it all again, and it worked (for now). I don't know what was the cause. I though I'd had tried everything, but it's working now so I'll never know. Thanks for your help guys!

answered Feb 17, 2012 at 13:42

Quarra

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Comments

davidcesarino · Accepted Answer · 2012-09-27 00:36:43Z

0

Nothing mentioned above worked for me. However, I fixed it myself.

Solution:

If you've any other files except activity_main.xml / main.xml inside app_name/res/layout remove it and try clean and build.

Note:

The unwanted files or (rather used later) files inside app_name/res/layout would be *.out.xml. Remove the same.

edited Sep 27, 2012 at 0:36

davidcesarino

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answered Aug 6, 2012 at 10:41

Dina

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Dilshad · Accepted Answer · 2012-11-20 11:56:23Z

0

Make sure that you are extending Activity class

answered Nov 20, 2012 at 11:56

Dilshad

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1 Comment

Parth Soni Over a year ago

Please always elaborate your answer

Community · Accepted Answer · 2017-05-23 10:26:59Z

0

I've had a similar problem. Tried everything and gen folder remained empty. It had to be with the SDK version 22. I hadn't installed the "Android SDK build-tools". I just had to install it with SDK Manager and restart Eclipse. As a member pointed on another post, the answer is better explained in this link: https://stackoverflow.com/a/16643060/1691231

edited May 23, 2017 at 10:26

CommunityBot

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answered Jul 6, 2013 at 2:28

Leo

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AJay · Accepted Answer · 2013-08-14 19:06:56Z

0

What you really need to do it just install "build-tools" from sdk manager, and r.java will be generated automatically in gen folder :)

answered Aug 14, 2013 at 19:06

AJay

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Martin Koubek · Accepted Answer · 2015-01-05 13:14:40Z

0

Simple

Check that you have the same SDK - build version with your AndroidManifest and project.properties version.

answered Jan 5, 2015 at 13:14

Martin Koubek

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