I just updated the SDK tools in Eclipse to revision 22, and since then I cannot build my project. Specifically the R class is not recognized in my Activity (I was getting compiler errors) and even when I imported manually, again the import was not working.
Additionally the project gen folder is empty, and cleaning the project/workspace (having build automatically option on) didn't make any difference.
Is this a known issue? Did it happen to everyone? Is there a workaround? Maybe Google just wants us to switch to Android platform the soonest possible?
I had major issues with the update as well. In my case my project uses a library that also depends on another library. I found that I needed to check the box for Android Private Libraries in the order/export tab of the Java Build Path for the project - and each of my connected libraries -- to properly compile and run the app on a device.
Some others have indicated that you need to also check Android Dependencies too but that doesn't seem necessary for my project.
Yes it's right. I had the problem too, there is a new "Android SDK Bild-tools". Open the Android SDK Manager and make a update, maybe twice.
More info:https://groups.google.com/forum/?fromgroups=#!topic/android-developers/rCaeT3qckoE%5B1-25-false%5D
I had this same issue.
In the project properties, Java Build Path, Order and Export section, I had to make sure the Android Private Libraries was checked.
Then I had to clean the project. After that it seems to work.
It was indeed an issue with 'Order and Export' of the Java Build Path.
When upgrading, the 'Order and Export' of the new 'Android Private Libraries' is not always checked. And the android-support-v4.jar is now in this 'Android Private Libraries' section.
To fix this, go to 'Order and Export' and check 'Android Private Libraries'. Then refresh/clean/rebuild.
After you done this 'fix' for a library project, you may need to just close and re-open any depending project, because they may not see this 'fix' immediately.
I found the answer here.
Same error i am also having, After i delete the empty gen folder it created automatically with files like R.java and all error has gone working fine
I am on windows 7, I had the same problem and merely making eclipse to "Run as administrator" and installing the packages again worked for me. (I had to do it even though I was logged in as an admin)
来源：https://stackoverflow.com/questions/16583786/android-sdk-tools-revision-22-issue