Question

I am working with JList and I have encountered a few design problems.
what I want is a gui componenet that presents a list and lets the user add or remove values from it.

So I have created a class that receives a list

List<? exteds IDisplayable> 

• IDisplayable is a simple interface that has String DisplayString(). every objects that wants to be displayed in the list needs to implement IDIsplayable.

When my GUI form loads I iterate over the list and do a

MylistModel.addElement(iDisplayable.getDisplayString()

This is because I don’t want it to display the toString(). So I added a method.

Now my question is how to return the list to the gui form that called it.
Should I iterate it and compare by name? This sounds awful.

I thing I need to put in my ListModel the object but display a different toString.
Should I create a new listmodel? I can’t even extend the AbstractListModel cause it uses toString.
Is that the only solution?

Answer 1

As already mentioned, a xxRenderer is the collaborator which decides about all visual representation of an item shown in a “collection component” (such as JList, JTable, etc …). When stuck to core Swing support, the way to go is a implementing a custom renderer. SwingX supports a more lightweight approach by allowing to plug-in string display (and visual decorations, but that’s a story different from this): implement a custom StringValue (SwingX speak for string converter) and pass it to a SwingX renderer like

StringValue sv = new StringValue() {
      @Override
      public String getString(Object value) {
          if (value instanceof MyObject) {
              return .... // use MyObject properties to build a suitable rep
          }
          return TO_STRING.getString(value);
      }    
}
list.setCellRenderer(new DefaultListRenderer(sv));
// a bit of beauty: same rep is re-usable in other collection components
table.setCellRenderer(MyObject.class, new DefaultTableRenderer(sv);
comboBox.setRenderer(list.getCellRenderer());
tree.setTreeCellRenderer(new DefaultTreeRenderer(sv));

In other words: SwingX supports a unified string representation throughout all of its collection components. The full power of that approach shows when sorting/filtering/searching: all that functionality automagically uses that custom string representation, that is the users by default sort/filter/search by what they see – no additional effort required by the developer 🙂