I was having a project open in Android studio. It was generated by the wizard and working fine.
I did some small changes to activity_main.xml and when I changed back to MainActivity.java i get the error in several places that it cannot resolve R. I might have done something to cause this. But I´m not sure what since it appered when I edited the xml.
Does anyone know what might be the solution to this?
I can find the R.java in r/release/packege/com/ and it looks fine.
Most of the time it is due to a bad XML file. XML files can be layout files, value files, or the Manifest file. Please check your xml files and try to rebuild the project. Sometimes cleaning the project and rebuilding it also works.
In addition, make sure you do not have a drawable with an invalid name. I had a drawable with a numeric filename and that didn't sit well with Android so it failed to compile R.java.
Downgrade Your Gradle Plugin Version
No amount of cleaning, rebuilding and restarting would do the trick for me.
The only thing that did the trick was downgrade our Gradle version from 3.4.0-alpha02 to 3.2.1.
So, instead of:
dependencies {
classpath 'com.android.tools.build:gradle:3.4.0-alpha02'
}
We used:
dependencies {
classpath 'com.android.tools.build:gradle:3.2.1'
}
After making that change and then doing a Gradle sync, everything worked.
Not sure if it's related to the alpha release or to that version or if changing your Gradle version at all just forces a refresh that otherwise cannot be done with the other commands, but there ya go.
Make sure in your AndroidManifest.xml the package name is correct. That fixed the problem for me when my R.whatever was marked red!
Try to clean the project by doing the following:
If you are using Windows, open CMD, cd to your project directory and run gradlew clean.
I just had this problem and the reason was that after editing the layout android studio automatically added an import to the source files:
import android.R
Of course the main R class has not all the symbols in your layouts, which made everything a red mess.
Removing that line solved for me.
EDIT:
Seems like eclipse had the same problem early on.
I sometimes get this after updating Android Studio. Not always straight away but after a while (perhaps after a restart of the program).
Here is what has worked for me: Tools - Android - Sync project with Gradle files.
For some reason just clicking the "Sync now" link that shows up after changing the build.gradle file has not done any change for me. Even though the messages says approximately the same thing.
I had the same problem because in my strings.xml I forgot to escape a apostrophe. Use " \' " never " ' " in xml file!
I had that same problem crop up, too (most recently while I was at lunch--came back and WTF?). And since this was a simple Hello, World program, there wasn't many places these errors could hide. The XML files looked fine--I hadn't even touched the manifest. A clean did nothing.
So I commented out a section of my layout.xml to try to narrow down the problem. Sure enough, the errors went away.
And then I simply UNcommented out exactly what I had commented...and everything was hunky-dory. Strange! Perhaps there was some lingering issues that needed to be touched in order to cause a rebuild of the layout file. You'd think basic stuff like that wouldn't happen these days, but they do.
One more thing! It's possible that something may happen to Java as well. It's very hard to know the status of the Java run-time environment; just easier to start again. So here's one more thing to try: restart your computer, restart Android Studio, AND THEN Invalidate Caches and Restart. Yep, the whole-hog.
When all else fails restarting android sometimes helps. During the start files are loaded afresh and this enables detection of the R
This problem occurs when you rename the package name.
After renaming the package name, you must change the older package
name to a newer one.
For me it solved the problem once I changed that.
After that, you might get errors in xml files, that you have to change
the package name there also.
That's it.
I just had the R problem and after a few hours found that the problem was my regional spelling as used in one of my xml files. The problem word was behaviour, which is spelled behavior by Americans.
I am Australian and we are taught ye olde English way of spelling certain words and so I looked past it a number of times before the penny dropped.
Its a small thing, but it can easily sneak up and bite you on the nether regions and is hard to spot and can waste a lot of time.
In my case I had just added some new image files to the drawable folder and accidentally put a GIF in there with my PNGs. I had not incorporated them into the project at all yet. I removed the GIF and then did a clean and rebuild. That fixed it for me.
I had this exact problem when importing a Udacity Example Program. The Message Pane in Android Studio said the error was failing to load a .PNG in a sub-directory deep in the Project Files.
Turns out the PNG with all of the sub-directory path names was greater than the name length limit defined by Windows 7 (260 characters). I gave the Project a shorter name - to free up some space - and then Android Studio happily compiled.
After you tried make project, clean project, rebuild project but still doesn't work.
Try restart Android studio
Newbie Alert: while working on my android application my program was acting kind of buggy so i went to project, and did "clean." i reimported my R but for some reason all my other classes and xml files are giving me errors "Cannot be Resolved or is not a Field"
i've restarted my eclipse and refreshed and im still getting these errors. Help please!
I come across this error often as well. Here's how to fix it:
Check your xml layout files for any errors. Fix any you find.
Delete all the "import" statements on the .java files that has all the "cannot be resolved or is not a field" errors.
Clean. (Project -> Clean...)
Re-import needed packages (Source -> Organize Imports) (Control + Shift + O). If a dialog pops up, choose carefully!
Save.
Basically you need to have < your package name >.R imported if you are using layout files.
If you have recently renamed a package, that could have caused this. Fix all the import statements so that they import the correct R, < your package name >.R
This has happened to me a lot as well. I found that it was usually a problem in one of my xml layout files such as missing a closing carrot or something like that. Just double check your xml's to make sure that you didn't forget something.
I had this problem too and i realized I have imported the wrong R.
Way to fix this,
Delete the already Imported R
Press Ctr + Shift + O and choose the R.
Save
Repeat the process and choose another R if it still has error.
I am doing an application in which I didnt changed anything and still it is giving me an error on R.java file that R cannot be resolved to a variable...
I have done all the things like: project->clean
close and open the project again
close the eclipse and restart it agagin but no solution...
I am not able to fix this problem....This problem is so much irritating....Can anyone pls help me in this case??
There is probably an error in one of your resource files, you need to properly check all your resources to find if any of them contain errors. The resource with an error will have an error red cross on its icon. Hope this helps.
Make sure there are no other errors that might cause this error, also look at this entry:
R cannot be resolved - Android error
If I make a new Android project in Ecplipse and I try, to open one of the samples from android SDK, I have got an error, look like this:
R cannot be resolved
What can I do, to be able, to run these files? I tried to delete import android.R; but nothing changed.
Thanks
First thing you might try is "clean" your project (option in the menu). If it persists:
There should be an error that stops R from being generated. Check the "problems" tab (?) in eclipse to see what that problem is, and solve that. It could be missing libs, or various other stuff.
You possibly got error in building resources.
Possible fixes:
-refresh your project (F5)
-clean you project and refresh
-see "Console" tab, sometimes the problem is shown there
-reload the Android SDK
-restart the Eclipse IDE
Check your XML-Layout files. The problem come here half a time.
If you are sure it is note your layout file, check in your java build path if the google librarys are well set. (Google APIs)
(sorry for my bad english)
I created a new xml file, and had an errant ? in it that prevented R.java from regenerating. I tried Cleaning the Project, and Fixing the Project Properties but no luck.
Then I realized the XML was creating the R.java from recreating itself, so I deleted the XML file and the R.java was back.
Now though, I am getting an error on all the calls to R.. calls saying that :
cannot be resolved or is not a field
So, for instance I have
setContentView(R.layout.detectlayout);
ERROR: detectlayout cannot be resolved or is not a field
for all of my calls to 'R.'. Any ideas?
I have tried all of the suggestions on SO already to no luck =/
Look at the 'import' section of your code. Since you deleted your original R, chances is Eclipse help you to fill in the R as com.android.R instead of com.yourproject.R
I also sometimes have problem in Eclipse Resource stuff, sometimes I found turning off and on the "auto buiild" function may help, or simply restarting Eclipse may sometimes help. It's kind of buggy under Mac OS.
This can happen if .R is imported. Eclipse will automatically add it sometimes when you have difficulty with with R.java
first don't bother deleting the R file it not going to make things better only worst lol
as you said you some times need to clean the project
when you start modifying resources its good to select the root of your project and do a alt+shift+o to reload all ressources
then f5 to refresh the tree
then clean the project
you also have to check that eclipse is set to build automatically (Project->build automatically).