How to get workbench/view in Eclipse (e4)? - eclipse

Question

I'm developing an Eclipse plugin in which I need to access a view.
I've found this way to get the workbench, but I guess it only worked in Eclipse 3.x and I am using Eclipse 4 so it doesn't work:
IWorkbench workbench = PlatformUI.getWorkbench();
IViewPart part = workbench.getActiveWorkbenchWindow().getActivePage()
.findView("id_of_the_view");
I then found this way:
#Inject
private static EPartService epartService;
MPart mPart = epartService.findPart("id_of_the_view");
MyViewClass part = (MyViewClass)mPart.getObject();
which throws a NullPointerException. I've made sure the view is open.
What am I missing?
Edit:
I've also tried this, as found here (german)
#Inject
private static EPartService epartService;
#Inject
private static MApplication application;
#Inject
private static EModelService modelService;
...
MUIElement element = modelService.find("id_of_the_view", application);
if(element instanceof MPart) {
MPart part = (MPart) element;
...
}
but I also get a NPE in the .find()-line.

Answer 1

You're right. In E4 you should use injection.
To avoid NPEs, you can get the reference to the IEclipseContext in part constructor.
public class MyPart {
private IEclipseContext context;
#Inject
public MyPart(IEclipseContext context) {
this.context = context;
}
}
Assuming you have your part class defined in a plugin, and that the class is referenced as Part in an E4 Application, you can get a reference to the Part instance using its id
Somewhere in your code you use the id to get an instance of your part
// somewhere in your code ..
// (where you can access the context instance)
MPart myPart = getPart(context, "com.example.myPart");
The easy way is to use EPartService.findPart() , as follows:
/** with this method I can get reference to the part */
public static MPart getPart(IEclipseContext context, String partId) {
EPartService partService = context.get(EPartService.class);
MPart part = partService.findPart(partId);
return part;
}
Beware of static methods. Context Objects and static members are not friends !!
For multiple matches, or advanced searches, you can use EPartService.findElements(), as follows :
public static List<MPart> getParts(IEclipseContext context,
MWindow workbenchWindow, String partId) {
EPartService partService = context.get(EPartService.class);
EModelService modelService = context.get(EModelService.class);
List<MPart> parts =
modelService.findElements(workbenchWindow, partId, MPart.class,
null, EModelService.OUTSIDE_PERSPECTIVE
| EModelService.IN_ANY_PERSPECTIVE
| EModelService.IN_SHARED_AREA);
return parts;
}