Developing for Android in Eclipse: R.java not regenerating

Question

I've found out that my R.java is never updated, so it doesn't contain information about my new resources, so I decided to delete it and thought that Eclipse would generate a new one. But that didn't happen, and I don't have R.java now. How can I regenerate one?

I'm using Windows 7.

From one of the comments: "Doing Project -> Clean is what caused the problem for me. Cleaning deletes R.java...and for whatever reason the plugin is not regenerating the file."

Answer 1

I had an error in AndroidManifest.xml file, so after fixing that error and hitting

Run->clean

it produce me R.java

Answer 2

First of all, check the Console output.
Then, check if your xml layout files names are lower-case only.
Correct xml errors.
Check Project properties -> Android for something unfamiliar

Answer 3

You 100% have an error in an XML-file, but the XML verification does not show you the error. This is the reason why you need to check your XML files first!

Answer 4

If you use the Lint error checker it will identify spurious import of "R". Once the XML system gets hold of the wrong end of the stick all is lost!!!

Answer 5

My problem was that appcompat was not in the same directory as my project.

I found this out when compiling my app with Ant.

Answer 6

In my case I checked all previous the solutions but not generated R. I just removed my main.xml file from the menu folder and regenerated it again. I don't know why, but it is working for me now...

Answer 7

If your OS is Ubuntu, I can provide some suggestion:

1. Install or upgrade ia32-lib:

   sudo apt-get upgrade ia32-libs
   

2. Check if you have the right permission on the aapt folder:

   cd ANDROID/adt-bundle-linux-x86_64-20130522/sdk/build-tools/android-4.2.2
   chmod 777 aapt
   

3. Start Eclipse:

   sudo eclipse
   

4. Run Project -> Clean in Eclipse

Answer 8

There is also another situation that happened to me. It was when I added a string with an apostrophe in my strings.xml resource file, like

<string name="Today">Returns Today’s date</string>

It was fixed by changing the apostrophe for another type of apostrophe, like ´.

Answer 9

What also causes this is if you have a scale9 drawable with the same name as another file:

• img_file.9.png
• img_file.png

Simply removing either one of the files fixes it.

Answer 10

Android has added in SDK build tool ADT 22 for the building mechanism. You just need to do the following steps.

1. Update Android SDK Tool
2. Update Android SDK Platform Tool
3. Update Android SDK Build Tool
4. Add the path of your build tool to the path variable. (path up to---- YOUR DIRECTORY-PATH\android-sdk\build-tools)

This will solve the issue.

Answer 11

If all answers fails, you can run the resource generation from command line: Go into your Eclipse project directory. Then run

aapt.exe package -f -v -m -S res -J src -M AndroidManifest.xml -I ANDROID_HOME/platforms/android-XXX/android.jar

Just change ANDROIRD_HOME and XXX with appropriate values. You should get on-screen information where the error is.

Answer 12

See blog post Android Developer Tip: Regenerating R.java.

Rather than continuing the discovery of all the conceivable strains of the issue found in the wild, I decided to leverage the tried-and-true approach of staring at the code. Having done so for a while I spotted a few red guys under the res folder. They were a leftover of my current redesign work that I was about to delete before things went awry. Sure enough, as soon as I hit Del on them the darn R thing automagically reappeared.

In single sentence: Remove all unwanted files from the project and unwanted code from the manifest file.

Answer 13

There were no errors but three warnings where I had used hard coded text for button text attributes in my main.xml. Something like this:

<Button
    android:id="@+id/scan"
    .....
    android:text="Scan" />

After changing text attribute to android:text="@string/scan_device" the R.java was immediately generated.

So, it always occurs on my machine/Eclipse whenever there's any error/warning in one of the XML files.

IntelliJ IDEA doesn't have this problem for warnings though.

Answer 14

I found this happening to me with a broken layout and everything blows up. Relax, it's like that old mistake when you first learned programming C where you forget one semicolon and it generates a hundred errors. Many panic, press all the buttons, and makes things worse.

Solution

• Make sure that anything the R. links to is not broken. Fix all errors in your XML files. If anything in the ADKs are broken, R will not regenerate.
• If you somehow hit something and created import android.R in your activity, remove it.
• Run Project -> Clean. This will delete and regenerate R and BuildConfig.
• Make sure Project -> Build Automatically is ticked. If not, build it manually via Menu -> Project -> Build Project .
• Wait a few seconds for the errors to disappear.
• If it doesn't work, delete everything inside the /gen/ folder
• If it still doesn't work, try right-clicking your project -> Android Tools -> Fix Project Properties.
• Check your *.properties files (in the root folder of your app folder) and make sure that the links in there are not broken.
• Right-click your project > properties > Android. Look at the Project Build Target and Library sections on the right side of the page. Your Build Target should match the target in your AndroidManifest.xml. So if it's set to target 17 in AndroidManifest, make sure that the Target Name is Android 4.2. If your Library has an X under the reference, remove and re-add the library until there's a green tick. This might happen if you've moved a few files and folders around.

What to do if R doesn't regenerate

This usually happens when you have a broken XML file.

• Check errors inside your XML files, mainly within the /res/ folder
• Common places are /layout/ and /values/, especially if you've changed one of them recently
• Check AndroidManifest.xml. I find that often I change a string and forget to change the string name from AndroidManifest.xml.
• Check that Android SDK Build-tools is installed. Window -> Android SDK Manager -> Tools -> Android SDK Build-tools
• Make sure when you update the Android SDK Tools, you also update the Android SDK Platform-tools and Android ADK Build-tools. Build fails silently if they don't match.
• If you can't find the issue, right click /gen/ -> Restore from local history... -> tick R.java -> click Restore. Even if it doesn't solve the problem, it will clear out the extra errors to make the problem easier to find.

Answer 15

1. Make sure your XML files are fine without any issues
2. Make sure your manifest has no errors in it
3. Make sure your strings have no problem in them

If any of them have issues, Eclipse might fail to build the R class... Fix the issues, clean & rebuild..

Answer 16

I can't see it listed here, but I encountered the problem of my R.java being removed and not being automatic rebuilt.

This happened to me when I was dealing with switch statements and strings. Eclipse suggested that I change my projects compliance to 1.7 which promptly broke the project (R.java) as Android can't use this compliance.

Console:

[2013-03-12 17:26:33 - CrimeAtlas] Android requires compiler compliance level 5.0 or 6.0. Found '1.7' instead. Please use Android Tools > Fix Project Properties.

I fixed the error by using "Fix Project Properties" and then going through the log like suggested. I commented out the XML in files mentioned replacing them temporarily with a LinearLayout. When it's fixed, bam, it reappears (if "Build Automaticly" is on). I can then change the XML files back if there was nothing wrong.

Answer 17

I had the same problem.

After checking Lint warnings I saw the warning The resource R.string.app_name appears to be unused..., so I deleted R.string.app_name.

This resource is required in AndroidManifest.xml although Lint warned me about an unused resource. I added "unused resource" to the manifest and everything went back to normal.

I hope this helps to someone.

Answer 18

I had a problem with my AndroidManifest.xml file and the R.java was not generated.

I think the solution is to check ALL of your XML files, everywhere!

Answer 19

I've found that any file that has capital letters in the res folder will create this error. This happened to me with a PNG file I added and forgot about.

Answer 20

Try checking the project.properties file. It might be the case that your Android JAR file in the build path doesn't match with the version mentioned over there.

It solved my problem as I had changed my target.

Answer 21

This problem just came up with me as well and unfortunately none of the suggestions here helped me. After trying a lot of things, I finally found out what happened and hope it can help others.

Yesterday I downloaded a lot of new stuff using the Android SDK Manager. After that I updated the Android Eclipse plugin. Today, after an Eclipse "clean", the R file vanished and stopped being generated.

The reason was that, somehow, the list of available SDKs (under preferences-> android) was empty. After pointing it again to the right directory it reloaded and showed the available SDKs. When I closed the preferences and tried another build, everything came back to normal.

In the image attached you can see the list of SDKs already filled. While the problem was happening it was empty.

I hope this can help others!

Answer 22

When nothing seems to work correctly even though you think that everything is right, check your XML files one by one. The mistake is there 100%.

If you work with the GUI of the XML files everything seems OK, but when you enter textual XML files you see the mess inside. Eclipse is a bit buggy for this stuff.

Set BuildAutomatically as well, so after you fix your errors you will have your R.java file in the generated ones.... GOOD LUCK!!!

Answer 23

R.java will never be generated if there are any errors in the res folder. For example, in the drawable subfolder there are two files which have the same name, one is icon.png and the other is icon.html.

You can see some error in the Eclipse console log window which is saying "Resource entry icon is already defined.". After deleting icon.html, you can clean or just delete the gen folder. You will find that R.java is created.

Answer 24

You can try one more thing.

Go to C:\Program Files (x86)\Android\android-sdk\tools>, run adb kill-server and then adb start-server. This worked for me, and I do not know the reason :-).

Answer 25

In my case, R files were not being generated because I had XML files in my res/ folder with the same name (for example, res/layout/filename.xml and res/values/filename.xml).

After I changed one of the filenames, my R files were generated again by the Build Automatically option.

Answer 26

Almost assuredly there is something wrong with the content that would be inserted into the genfile. Eclipse is not smart enough to show what the problems are or even indicate that there are problems!

Think about the last edit you made to any of the XML or image content - and try to 'rollback' your changes, manually if necessary.

I find that sometimes Eclipse does not like my file names for whatever reason, and I have to change them.

So add to the resources one by one assuring that it all 'works'. When something breaks, just try changing it a little bit until Eclipse accepts it.

You know it's working when the genfile appears - it will do so automatically if there are no problems.

Answer 27

I had the same problem. It turns out I had a circular reference; I changed a string name that was referenced in my layout.

I did a clean and rebuild and the R.Java file was not being recreated. I wasted two hours trying to figure out what was wrong. I eventually changed the layout item to some temporary text, did a clean project and the R.Java file was created.

Answer 28

For me, the problem was that I had an image in my res folder with an uppercase letter, that is, Image.png. Just put image.png.

All to lowerCase and that's it!

Answer 29

If your AndroidManifest.xml file is referencing String constants that you have stored in strings.xml, and you rename those Strings in strings.xml, you'll need to change them in the manifest to make everything kosher for a build.

The same would go for any layout .xml files that are referencing those constants you changed. Unfortunately, neither the Markers view nor the Problems view in Eclipse will tell you where you need to go to fix the issues--just that they can't find R.java. As mentioned in other answers, look at the Console to see where you need to fix your constant references, and then clean your project again.

Answer 30

This problem also happened to me when I was trying to build the Support4Demos from the SDK source code.

After fixing some problems in the resource files (for example, "fill_parent" renamed to "match_parent") I've discovered that the problem was in the manifest file: I unchecked by trial and error the "Define an <application> tag in the AndroidManifest.xml" checkbox, saved the changes and the R.java magically reappeared. Then I re-checked the box, saved the file, and the R.java was regenerated again.

I guess I came across an Eclipse shortcoming.