项目清理后，R.java消失了

Question

After I added some .png files into my Project Workspace drawable folder I refreshed my drawable folders in Eclipse and the newly added files showed up. But when I tried to access those resources using R.drawable.xyzimage, xyzimage although in the folder could not be resolved.

So I did a Project Clean and guess what after this clean R.java is totally gone and all my classes accessing resources using R.java is showing all sorts of error and Eclipse won't let me run the code anymore.

I have backup of my source code but I want to explore if R.java can be regenerated and how?

Thanks for all the help.

Answer 1

Try Project->Clean in Eclipse. In my limited experience if R.java is not being automatically created then there is an error somewhere in your xml. Triple check everything.

Answer 2

You have to build the project to be able to use the newly added resources.

Cleaning a project removes all auto-generated files. Building the project it should automatically create them. When you Clean a project, there's an option to start a build immediately after clean up.

Here's a few things you can try (did the same procedure after manually deleting the " gen " directory.

• After you have deleted the gen directory, go to Project > Clean ...
• You should have errors indicating that R cannot be resolved to a variable. Right click on your project from the Package Explorer and select Build Project. Be sure Build Automatically option is turned off (uncheck in Project > Build Automatically).
• Errors regarding R should have now disappeared. Now, perform a Project Clean once again. All errors should be gone.

Let me know if this works for you.

Answer 3

Here is what the problem was. I added those new png images to the project and android has rules as to what characters are allowed in the names of these images. Once I changed the uppercase letters in the image name, it was back on track again and Build Automatically generated the R.java file and all errors were gone. Eclipse console is the place where I found all the errors related to my resources.

Thanks Guys....I tried your solutions but my error was something specific which was due to my image naming convention so this is the way I fixed it.

Answer 4

I would agree this is usually a XML problem but moreover that it is something within your res folder that is the problem and may be highlighted with a red cross after the clean attempt.

I have just had this problem and it was because I had created my own folder called 'data' within res folder. After the clean it had a little red cross against it. I removed this folder and R built again.

Regards, Mark

Answer 5

Everytime you clean the project and it rebuilds, it imports

import.android.R

so, delete this import and remove all errors from xml files. It will work.

Answer 6

Several things you should check in your project:

• Check the Problems tab in your Eclipse IDE. Are you sure that you did not introduced building problems while making changes with drawables? To check that you need to check xml source of affected layout and see if something is marked red.

• In File explorer go to the directory where your Android project is. Check that you have file default.properties (.classpath, .project and AndroidManifest.xml should be there). If default.properties is missing it may be easily replaced by correct version.

• Which is the Android version you are working with? If that is 1.5 or lower be sure that in the res directory you have directory named drawable , not drawable-hdpi , drawable-mdpi and drawable-ldpi . Last three are valid for version 1.6 and higher.

• Right click on your project in Package explorer in Eclipse. You will get a number of options. Go to Android Tools-> Fix Project Properties so see if that helps.

Answer 7

I had an invalid jpg in my res/drawable folder. I removed the jpg and it worked.

Answer 8

I had this problem on my Mac too and I think it could be good to know for all Mac users how I managed to solve this error.

I had a .DSStore file automatically imported to my project inside the res directory and when I removed it and rebuilt the project all went well.

Answer 9

This may be simple but check to make sure you don't use

import android.R;

Answer 10

If you add an external resource file with capital letters for example "Hello.png or WelcomeSound.mp3 etc etc" like if you add upper case letters and clean your project you'd surely loose your R.java file. So if you already lost it, either rename the file externally and then clean your project or else right click on the project Refractor->Rename and then rename your file with all letters in lower casing. Next, delete the 'gen' folder in the project explorer and now right click and "Build Project". If Build Project option is grayed out, go to Project-> Deselect "Build Automatically" option.

Regards,

Kshitij Thube

Answer 11

Check at the Console View If there in message Error, It will Help you to find out the source of the probleme. I had i similar probleme and i find out that the probleme was from the pic name even if the name respect the Syntax so I change it to img1 and it worked fine.

Answer 12

This happens to me if I move my project to a new location. I have found that the answers above didn't fix my problem, but that creating a new project and importing the source did.

Answer 13

All my R.* files stopped working after I did a Project->clean in Eclipse. The issue was that I backed up a XML file attached to one of my activities in the layout directory. This causes errors in every activity of my project.

After deleting the file I still had R errors in one of my Activities and it only was resolved after I tried importing different files and then deleting them. I actually made no change to the previous imports but for some reason deleting them all and re-pasting them fixed it.

Answer 14

Make sure your png files have lowercase names. That is what kept throwing mine out, because I capitalized the first letter, or I used an unallowed non alpha numeric in the naming. Check that before destroying any of your code.

Answer 15

只需检查您的图像文件夹（通常创建res>可绘制文件）并确保不要在.png文件上使用大写字母，每个类型必须是小写字母然后您可以再次找到您的R.java在gen文件夹下

Answer 16

i removed 'import android.R;' then commented out the offending lines, then did a build, ok

then i removed the comment and it fixed it

Answer 17

I had the same problem when I cleaned my project. I got crazy to solve it, I searched and searched but solved it in my way. First of all, delete all needless files in your /res folder . I had some notes in it, I took them to another project that I don't work on it and build the project manually. It worked! Try this I'm sure it will help.

Good developing!

Answer 18

Was there an XML file with the naming convention of "somthing.out.xml" generated? If so you should delete this file (an unwanted file of this name can cause major problems for your somthing.somthing.R file import).

In some versions of eclipse (I know eclipse javaEE does this for sure), running the project while viewing an XML file will create a file called filename.out.xml in your res->layout folder. You must delete this generated file if this has occurred otherwise you wont be able to get the java.R file to import.

Answer 19

尝试项目 - >自动检查构建

Answer 20

If you are using 64-bit Ubuntu, try to install the 32-bit libraries (ia32-libs)

$ sudo apt-get install ia32-libs 

it worked for me

Answer 21

This exact same thing happened to me. coincidentally I needed to update my adk that day, so i did so and after restarting eclipse it worked again. My recommendation would be to build the project and restart eclipse. It is not due to any error in your code.

Answer 22

I read and tried many of the above after simply doing a clean on one project. Eclipse would not build anything afterwards.

Fortunately I had last-nights backup of the workspace and my source is copied in from VS 2010.

No more cleaning!

Answer 23

Delete your project from workspace witout source deleting and then import it into workspace.

RightClick on your Project -> Delete /Don't select "Delete project content on disk (cannot be undone)"/ -> Ok

File -> Import -> General -> Existing Projects into Workspace -> Brouse -> /Look for your workspace(!) folder/ -> Ok -> /your cleaned project will be automatically checked/ -> Finish

Answer 24

I had the dreaded missing R problem yesterday with Eclipse Juno after a routine clean. StackExchange is full of suggestions and extensive googling revealed only the usual suspects (XML naming conventions problems, etc) none of which seemed to apply directly, although it is certainly possible I missed something.

The best summary comprehensive list of possible causes and fixes was here:

http://www.techrepublic.com/blog/software-engineer/a-comprehensive-troubleshooting-guide-for-androids-r-cannot-be-resolved-error/

One useful tip there was to try to create and run a simple " Hello World " in my workspace. If that does not run, the setup is corrupted. My Hello World was just as full of errors as my custom app.

The solution that worked for me (perhaps great overkill but nothing else worked) was to completely uninstall Android SDK and delete Eclipse (Juno), download Eclipse for Developers (Kepler) and reinstall Android ADT plugin and ADK and recreated my AVDs using the latest "compile with" version in options.

So far so good, although I am recreating the app from scratch. I will be more cautious about using clean from here on.

Answer 25

我刚才遇到同样的问题我将无效的png文件重命名为* demo.1.png，作为demo.png *及其工作。

Answer 26

经过验证的成功方法，检查文件（AndroidManifest.xml）并删除其中的所有注释，并确保此文件中没有错误，我尝试过并与我合作。

Answer 27

尝试编辑项目中的一行代码，然后再次构建项目。

Answer 28

Another thing: never try to run an application with the texteditor opened with a xml file. That will create a wierd run configuration that can only be fixed by project clean-up and sometimes can make the xml file to vanish (happened to me twice already).

Answer 29

Check your file in drawable folder ensure that all are resource file (image) remove unwanted file Like thumb.db . Remove those all files and check again

Answer 30

I have got the same problem after lots of cleaning and building project again and again. I found that on console there is this error:

res/drawable-hdpi/Blue Blank.png: Invalid file name: must contain only [a-z0-9_.]

and this is not appearing as an error in xml. I changed the name and save the file, clean project and build. Now it's working. My suggestion check your res folder and name of files you use in it and name only [a-z0-9_.] .

Delete related tag in xml, save xml, clean project, build project. Now again put that resource in xml and save!