Question

I have a ContentProvider for a TreeSelectionDialog. I need to implement the getParent method in order to select the root of a tree if one of its nodes is checked. This is the code:

@SuppressWarnings("unchecked")
protected Node<T> getAdapter(Object element) {
    if(element instanceof Tree)
        return ((Tree<T>)element).getRootElement();
    else
        return (Node<T>)element;
}

@Override
public void dispose() {
    // TODO Auto-generated method stub

}

@Override
public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
    // TODO Auto-generated method stub

}

@Override
public Object[] getElements(Object inputElement) {
    return getChildren(inputElement);
}

@Override
public Object[] getChildren(Object parentElement) {

    if(parentElement instanceof org.db.normalization.Table) {
        if(((org.db.normalization.Table)parentElement).getStatus() == Status.DELETED)
            return new Object[0];
        List<org.db.normalization.Attribute> atts =  new  ArrayList<org.db.normalization.Attribute>();

        for(Attribute a:((org.db.normalization.Table)parentElement).getAttributes().getAttributes())
            if(a.getStatus() != Status.UNMODIFIED)
                atts.add(a);


        for(Attribute a:((org.db.normalization.Table)parentElement).getPrimaryKey().getAttributes())
            if(a.getStatus() != Status.UNMODIFIED)
                atts.add(a);

        return atts.toArray();
    } else if (parentElement instanceof org.db.normalization.Attribute) { 
        return new Object[0];
    } else {
        @SuppressWarnings("unchecked")
        List<org.db.normalization.Table> n = (ArrayList<org.db.normalization.Table>)parentElement;
        if (n.size() > 0)  {

            return n.toArray() ;
        }
    }
    return new Object[0];
}

@Override
public Object getParent(Object element) {
    // TODO Auto-generated method stub

    return null;
}

@Override
public boolean hasChildren(Object element) {
    // TODO Auto-generated method stub
    return getChildren(element).length > 0;
}

I really have no idea of what to write in the getParent method, since I have no other information than the element received as a parameter, and this element alone, doesn’t know its parent.

Thanks!

Answer 1

Most instances of a tree implementation, you do know your parent, so parents are either set by a setter method or on the constructor. You have no idea who the parent is, so you are presenting the worse case, where you basically have to get all node, and check rather the children of each node contain you.