Question

I have an operations class that has no gui. The class basically does data management. The class is called from a method in my Main GUI. The problem I am having is with displaying messages to the user if something fails. I am using MessageDialog, but it keeps failing at runtime. I think the issue is with Shell. When I try to use null as the shell.

MessageDialog.openError(null, "Printer Error Message", "Error getting print reply file.");

The error is null pointer exception

MessageDialog.openError(Display.getCurrent().getActiveShell() etc

The error is null pointer exception

MessageDialog.openError(Display.getDefault().getActiveShell()

The error is invalid thread access

1. Being this is not a GUI class, do I have to pass in the shell from the GUI parent?
2. Can I just create a shell in the class and then use that?

Answer 1

You can fix the ERROR_THREAD_INVALID_ACCESS error with Display.syncExec or Display.asyncExec . Try with:

Display.syncExec(new Runnable() {
    void run() {
        MessageDialog.openError(Display.getDefault().getActiveShell()...
    }
}