Eclipse: Getting null display

Question

I am trying to pop up a dialog (i.e. a FileDialog) in an Eclipse Plugin, actually before of an Acceleo transformation I am running through the related UI Launcher project (http://lowcoupling.com/post/51877317162/the-acceleo-ui-launcher-project)

I am trying to do this in the related doGenerate method...

public void doGenerate(IProgressMonitor monitor) throws IOException {

    Display display = Display.getCurrent();
    System.out.println(display);
    //....

but the display I get is null How should I do that?

Bebebebeerine

Answer 1

The documentation of IWorkbench#getDisplay() states:

Code should always ask the workbench for the display rather than rely on Display.getDefault().

So use:

PlatformUI.getWorkbench().getDisplay()

instead.

Pozsony

Note that this can't be used in a 'pure' e4 application where PlatformUI can't be used. For syncExec and asyncExec use org.eclipse.e4.ui.di.UISynchronize which can be injected. – Chalcidice

@Chalcidice Good to know. Haven't used e4 yet. – Pozsony

Answer 2

I'm not sure if you looked at this yet, but in the documentation for the class Display, it says that Display.getCurrent() returns

null if the currently running thread is not a user-interface thread for any display.

This might be the problem, but without more information I can't tell.

Aureomycin

yes this is the problem but I still can't see where to show the dialog – Bebebebeerine

Answer 3

You can try getting the default display Display.getDefault() or the workbench display PlatformUI.getWorkbench().getDisplay()

If you are not running in the UI thread, try the following:

Display.getDefault().syncExec(new Runnable() {
    public void run() {
        // ... do work that updates the screen ...
    }
});

Gooding

You are aware, that the second method you suggest states that using the first one is not recommended? ;) – Pozsony

Answer 4

I was facing the same issue. I used getShell().getDisplay() instead of Display.getCurrent() and it worked for me.

Fuegian