Android - How to regenerate R class? [duplicate]_问答_开发者

This question already has answers here: Closed 10 years ago.

Possible Duplicate:
Developing for Android in Eclipse: R.java not gene开发者_JAVA百科rating

I have imported a project into my Eclipse IDE, but it's giving me an error since R file is not generated automatically.

How can I edit the R file so that it matches my project requirements?

In another stackoverflow question, somebody answered this : you must get rid of warnings and errors (syntax and links) in your xml files. This plus doing a clean / build project.

Project -> Clean, and choose the option to build the project.

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 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. If it's broken, ADK may not regenerate R. Fix all errors in your XML files.
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.
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.

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.
If you can't find the issue. right click /gen/ -> Restore from local history... -> tick R.java -> click Restore. This doesn't solve the problem, but it will clear out the extra errors to make the problem easier to find.

I know there's already a lot of answers here, but this is the first link on Google, so I'm compiling all the advice here and hope it helps someone else new to this :)

Ok, I fixed it:

When I changed manifest to target 1.5 version, million errors appeared and only one wasn't related to inexistance of R class - in manifest file attributes "targetSdkVersion" and "maxSdkVersion" did not exist in sdk 1.5

Because of this R class was not able to generate.

I had a similar problem where the R.java file was not being regenerated after I'd added some icons and layout files. I tried cleaning and rebuilding and things got worse since then the original R.java file was gone and still wasn't regenerated. Eventually it dawned on me that there must be compiler errors for the compiler that generates R.java and we aren't being shown those in the console. Fortunately, I had noticed earlier that

it's an error if one .xml file refers to another which is non-existent and
it's an error to have upper case letters in your file names (why is that forbidden, I LOVE camel case).

Anyways, after renaming my icons and .xml files to all lowercase and then fixing all the references inside the .xml files, voila, R.java was regenerated. Just in time to feel good when I stopped for lunch :-)

To generate the R file again:

Modify something in layout->activity_main.xml
Save the file
Project->Clean...

Just delete the R file located in gen directory, and then try Project->Clean. Then build your app again.

You can also right click on the project -> Android Tools -> Fix Project Properties. That should cause the R.java class to be re-generated.

I reopen eclipse, edit one of my xml files and then discover that my activy class was refering android.R instead of my package "R" :-)

My problem was in Manifiest file. I have deleted launcher icons and did not reference the new ones on Manifiest :)

In order to regenerate the R.class, you will have to try multiple techniques.

Remove any R imports from your java source files: import R.android
Make sure to open the "Problems" panel by going to Window->Show view->Problems
If you do have some errors in your xml resources, you will need to correct those errors. In my case I had to change my id attributes to include the "+" sign as follows: android:id="@+id/grp_txt"
Now proceed to do Project->Clean
Finally do Project->Close, Project->Open

The "+" sign indicates a new resource id and the forces the aapt tool to create a new resource integer in the R.java class.

If you use Intellij IDEA you can click Build - Rebuild Project

If you accidently deleted your R in eclipse by "project clean" (don´t do this) Rightclick on your Projectfile -> Restore from local History...

recreate your R

My Case:

Broken xml caused bug in R. (because of ä, ö, ü, letters in id)
clean project deleted my R.

What I Did:

recreated R from local History
checked for wrong R imports in my classes (like import android.R) and removed them
fixed that xml file and saved its content in an external txt file
deleted the xml completely from my project.
ran my project one time
put that fixed xml back at its place

and...

gave my girlfriend a big hug without a reason after freaking out like a Hulk.

My problem was errors in my XML files. Errors aren't always automatically detected in the Android Common XML Editor or Android Common Manifest Editor, so try using the regular text editor instead. For example, somehow some random gibberish from a .java file had been inserted into my manifest and strings.xml files.

Right click on any XML files (most likely in the /res folder or AndroidManifest.xml) and click "Open With," then select "Text editor." Make sure everything looks good and then save. Also, make sure to enable "Build Automatically" for your project. I had deleted my R.java file and it was rebuilt from scratch, so no need to restore it from local history.

Try to add a new "Android XML file" to, for example, the /res/layout folder. This might cause the plugin to to regenerate the R class.

You can just modify any xml files in /res folder and even just add a space and save, it will be regenerated.

I had the same problem - "R" missing. And none of the advices given here helped. Fortunately, I've found the reason - somehow Eclipse got lost the Project-Properties-target. It was unset. I don't know till now, what had done it, but setting it back helped. So, attention - missing R can mean the missing target, too!

I have tried all the solutions above. But they unfortunately it did not solve my problem. My R.java was gone as soon as I pasted a new picture to my drawable folder. After reading the answers for this question I tried to delete the icon I have previously pasted (while Build Automatically Enabled) and everything was fine afetr. Hope this will help someone!

I had that problem and I just right-clicked on packet of my project and Build Project. Instantly the class R appeared in packet gen.

In case someone else finds this thread when Googling, like I did:

I had what appeared to be the same problem for a while, and after some digging I noticed that the R.java file got correctly built, but was ignored for only one of my source files. The problem for this particular file was that Eclipse had "helpfully" added the following line at the top:

import android.R;

That effectively hides the project R stuff. Just remove it and everything will be fine again...

You can use Eclipse's "Restore from local history" to restore your old R file if it has been deleted. After that you possibly see what keeps Eclipse from building your files (I've seen other errors than before which really helped fixing the problem).

May be you can go to project properties and select Android option and then define the target for the project. Once you apply the selected target API for this project, it will automatically generate R.java.

Mostly a problem with an invalid layout file. Open the 'Problems' view and look for erros in XML layout files. Fix them and the R class will be recreated.

In my case there wasn't a real error. The problem view showed an error in a xml layout. The editor showed the xml error too. Just reformatting the xml using the auto formatter with 'ctrl-f' 'fixed' the xml 'error' and the R class was recreated.

You can just delete the R.java file from your project and it will regenerate assuming you have build automatically enabled. If you do not have build automatically enabled simply goto project->build all

For me, it was a String value Resource not being defined … after I added it by hand to Strings.xml, the R class was automagically regenerated!

This problem normally happens when importing from an existing project. Try to fix all errors from all .xml files in res folder, as well as Manifest file. Most likely the errors are shown at "match_parent" parameter, change it to "fill_parent". When all errors are clear, R.java will be appeared.

If there is no error on any .xml file. Try edit any xml file (like delete a letter and type it back) and then save the file, this will cause to generate the R.java.

I have a problem that the findViewById(R.id.edit_text) but return a TextView not a EditText. I think the problem is the R.id class has wrong id number, then, i clean the project then its works fine.

In my case it was an improperly named XML file that caused my R file not to rebuild. This did not show up in the package explorer, but it was shown in the LogCat. Look out for any warnings there about your res files. No matter how many times you clean your project, the R file will not rebuild until those errors are taken care of.