NPE after adding AbstractDecoratedTextEditor to a Multipage editor in Eclipse

Question

I'm creating a simple Eclipse editor, this editor contains two pages, one of them is an editor that extends from AbstractDecoratedTextEditor , then in my multipage editor class I'm adding the editor like this:

MyEditor myEditor = new MyEditor();
addPage(myEditor, myEditor.getEditorInput());

When I launch the application, the editor looks like this:

This is my class:

public class MyEditor extends AbstractDecoratedTextEditor {

    public MyEditor() {
        setSourceViewerConfiguration(new SourceViewerConfiguration());
        setDocumentProvider(new FileDocumentProvider());
    }

    @Override
    protected boolean isLineNumberRulerVisible() {
        return true;
    } 

    public void init(IEditorSite site, IEditorInput input) {
       setSite(site);
       setInput(input);
    }
}

And this is the log:

java.lang.NullPointerException
    at org.eclipse.ui.texteditor.AddMarkerAction.getResource(AddMarkerAction.java:336)
    at org.eclipse.ui.texteditor.AddMarkerAction.update(AddMarkerAction.java:162)
    at org.eclipse.ui.texteditor.TextEditorAction.<init>(TextEditorAction.java:49)
    at org.eclipse.ui.texteditor.AddMarkerAction.<init>(AddMarkerAction.java:96)
    at org.eclipse.ui.texteditor.AbstractDecoratedTextEditor.createActions(AbstractDecoratedTextEditor.java:1153)
    at org.eclipse.ui.texteditor.AbstractTextEditor.createPartControl(AbstractTextEditor.java:3576)
    at org.eclipse.ui.texteditor.StatusTextEditor.createPartControl(StatusTextEditor.java:54)
    at org.eclipse.ui.texteditor.AbstractDecoratedTextEditor.createPartControl(AbstractDecoratedTextEditor.java:447)
    at org.eclipse.ui.part.MultiPageEditorPart.addPage(MultiPageEditorPart.java:243)
    at org.eclipse.ui.forms.editor.FormEditor.addPage(FormEditor.java:325)
    ....

Answer 1

Your MyEditor does not have an editor input set.

In your code:

MyEditor myEditor = new MyEditor();   
addPage(myEditor, myEditor.getEditorInput());

myEditor.getEditorInput() will be returning null because you have not set an input to the editor.

You must pass a proper editor input to the addPage call (often the input of the multi-page editor). This will then set the input in the editor.