After upgrading the ADT plug-in, eclipse suddenly experienced the unable to build: The file dx. jar was not loaded from the SDK folder error.

After the ADT plug-in is upgraded, eclipse suddenly displays unable to build: The file dx. jar was not loaded from the SDK folder error unknown error: unable to build: The file dx. jar was not loaded from the SDK folder! After upgrading the ADT plug-in, eclipse suddenly encountered the above error and failed to run the android project. If you have searched for many methods on the internet, you will not be able to do it if you have tried it. For example, you cannot copy dx. Jar under tools to the corresponding platform directory. You cannot restart eclipse and update the SDK. Finally, you can find a method on stackoverflow and try it before using platform-tools \ Lib folder was missing after upgrade (my eclipse was open ). close eclipse, using SDK manager uninstall and install "android SDK platform-Tools ". close eclipse, open the two check boxes under the top tools of SDK manager.exe under the SDK installation directory, and click the install packages button below to update. After the update is complete, start eclipse.

Note: Later, I found on another computer that the SDK cannot be installed if it is not updated to the two packages under the latest version of tools. Therefore, you must update the SDK before updating the tools.

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Another reason is that eclipse cannot generate R. java file. Many methods are searched online to generate R. java, but the above cannot be run again.

The root cause is that the android SDK is upgraded and must be upgraded to the latest version for normal use.

For details, see another blog http://www.cnblogs.com/zdz8207/archive/2012/11/30/eclipse-android-adt-update.html