Question

I have two separate views that both show multiple lists of values. Both views are open at the same time.

I have a generic command AddNewItemInList that I want to add to the Toolbar of both views. The command should add a new item to the list that currently has focus. The command should be disabled if the user has not yet selected a list.

I currently have used the following to execute the command.

public class MyViewPart extends ViewPart {
    [...]
    public Object getAdapter(Class clazz) {
       if(clazz.equals(List.class))
           return getListInFocus(); // can be null if no list in focus
       return null;
    }
}

public class AddNewItemInList extends AbstractHandler {
    @Override
    public Object execute(ExecutionEvent event) throws ExecutionException {
        MyList list = HandlerUtil.getActivePart(event).getAdapter(MyList.class);
        list.add(new Item());
        return null;
    }
}

So far so good, but I have no clue how to enable or disable the Handler accordingly. I have read about the Eclipse Core Commands framework. I am very lost.

Answered questions:
How can I create an expression to see if the getAdapter() method of the view does not return null? -> Answered below

How do I get the view for which this command was configured (and not the currently active view) ? -> I can add the viewId as a command parameter

Remaining questions:
Should I configure two separate Handler instances in my plugin.xml (one for each view) ? -> The enabledWhen condition can only use the current evaluation context. It seems I cannot use any parameters provided by the command. This means a handler is either enabled or disabled depending on the state of the full workbench.

Answer 1

How can I create an expression to see if the getAdapter() method of the view does not return null?

You can use custom property testers. It needs a lot of boilerplate and looks ugly, but it works.

EDIT: Actually, it’s a lot simpler:

<with variable="activePart">
  <adapt type="com.foo.MyList"/>
</with>