Custom Jar files not showing in SmartDashboard

Im trying to use the WPILib Cookbook’s example for getting vision tracking done the SmartDashboard, yet whenever I build the jar and place it in the SmartDashboard’s extension folder, I can’t see it in the SmartDashboard’s “Add” submenu. Here’s the code for the jar :

public class VisionSystem extends WPICameraExtension {
    @Override
    public WPIImage processImage(WPIColorImage rawImage) {
        return rawImage.getBlueChannel();
         }
}

There are two potential ways this is happening. First, make sure that you restart the SmartDashboard after you drag something into the extensions folder. Second, make sure you start the SmartDashboard program by double-clicking the jar that is in the SmartDashboard program file folder.

I hope that that helps.