Android Error – java.lang.NoClassDefFoundError for No Apparent Reason

This error can show up unexpectedly -everything was working fine and suddenly you get this error- or after updating the ADT.

The following error appears in the Log, coming from one of the classes we created:

E/AndroidRuntime(5410): Caused by: java.lang.NoClassDefFoundError: miPropiaClaseDeEsteProyecto

 

It can also happen with an imported library, for example the "libGoogleAnalyticsV2.jar" library, showing:

E/AndroidRuntime(5410): Caused by: java.lang.NoClassDefFoundError: com.google.analytics.tracking.android.EasyTracker

Or, for example, with the "gcm.jar" library, showing:

E/AndroidRuntime(5410): Caused by: java.lang.NoClassDefFoundError: com.google.android.gcm.GCMRegistrar

 

Solution 1

We’ll try cleaning the project.

Note: We recommend making a backup copy of the project before continuing. Cleaning is usually safe, but sometimes it cleans more than it should.

To do so, go to the toolbar, click "Project" and, in the drop-down menu, choose "Clean…"

In the window that opens, select "Clean projects selected below" so you can pick the project you want to clean, select it and click "OK".

Check whether it works. If it still doesn’t, try solution 2.

 

Solution 2

First, check that the folder containing the jar files is named "libs".

 

If it isn’t, you need to rename it (sometimes it’s called "lib" without the "s"; "lib" without the "s" is wrongly named, so rename it to "libs"). To rename the folder, right-click it, then choose "Refactor" and then "Rename…". In the pop-up window that opens, enter the name "libs" and confirm.

Once that’s done, we continue. Right-click the project. Select "Build Path" and then "Configure Build Path…".

Go to the "Order and Export" tab. You’ll most likely see that the ".jar" files are unchecked. Check all of them (you’ll probably have the one called "android-support-v4.jar"; in this example you can see two other libraries widely used in Android, "gcm.jar" and "libGoogleAnalyticsV2.jar", and you might have others). Click the "OK" button.

Give it a try. If it still doesn’t work, clean the project one last time (do or redo solution 1 and test again). Everything should now be working correctly again.