I have managed to make your SS4 skin work without the error, the solution is below.
However, if you used Netbeans you would not have these types of problems.
Solution:
In onload.bsh add these imports
import se.datadosen.component.StateMonitor;
import se.datadosen.jalbum.JCustomPanel;
Move the blocks of code
// Make some convenient references available
JAlbumContext context = JAlbumContext.getInstance();
PluginContext pc = context.getPluginContext();
EditPanel editPanel = pc.getEditPanel();
CustomUI CustomUI = new CustomUI(context);
// Install custom panel in Jalbum's edit panel
editPanel.addCustomTab("Panoramic image", CustomUI);
// Make some convenient references available
JAlbumContext context = JAlbumContext.getInstance();
PluginContext pc = context.getPluginContext();
EditPanel editPanel = pc.getEditPanel();
CustomUI customUI = new CustomUI(context);
// Install custom panel in Jalbum's edit panel
editPanel.addCustomTab("Link", customUI);
to the end of the onload.bsh file, that is
after // Finally install components into JAlbum
window.setSkinUI(ui);
Note, I have not looked for other imports that might be missing,
you cannot use a standard set of imports, it just doesn't work that way.
Edited by: jGromit on 20-Jul-2019 18:25 - onload.bsh, not init.bsh
Edited by: RobM on 20-Jul-2019 23:30
Oops, sorry - late and drunk
Edited by: jGromit on 20-Jul-2019 18:32
Early here. But also drunk. Temps hit a comfy 35°C this afternoon. Many gins and tonics....