jList - 添加元素并显示String？

Question

what's up?

I created one jList on my project that I can't retrieve the element. I know jList only accepts objects, but I was adding Strings to my list, because when I add "Discipline" object, I see something like " Discipline{id=21, name=DisciplineName} " on my view. So, I'm adding strings instead objects.

Following is my code:

ArrayList<Discipline> query = myController.select();
for (Discipline temp : query){
    model.addElement(temp.getNome());
} 

When I get the index of a double click in one element, I try to retrieve my String to make a query and know what's this discipline. But I'm getting some errors, see what I already tried :

Object discipline = lista1.get(index); 
// Error: local variable lista1 is accessed from within inner class; needs to be declared final

String nameDiscipline = (String) lista1.get(index);
// Error: local variable lista1 is accessed from within inner class; needs to be declared final

I really don't know what means "final", but what can I do to solve this problem? One thing that I thinked is:

Can I add a Discipline instead String, show to user discipline.getName() and retrieve Discipline object?

Answer 1

Yes, add Discipline objects. A quick fix is to change Discipline's toString method, but a much better fix is to create a ListCellRenderer that displays each Discipline's data in a nice String.

Here are two ListCellRenderers that I have used in a project of mine to change the item displayed in my JList from text to an ImageIcon:

private class ImgListCellRenderer extends DefaultListCellRenderer {

  @Override
  public Component getListCellRendererComponent(JList list, Object value,
        int index, boolean isSelected, boolean cellHasFocus) {
     if (value != null) {
        BufferedImage img = ((SimpleTnWrapper) value).getTnImage();

        value = new ImageIcon(img); // *** change value parameter to an ImageIcon 
     }
     return super.getListCellRendererComponent(list, value, index,
           isSelected, cellHasFocus);
  }

}

private class NonImgCellRenderer extends DefaultListCellRenderer {
  @Override
  public Component getListCellRendererComponent(JList list, Object value,
        int index, boolean isSelected, boolean cellHasFocus) {

     // all this does is use the item held by the list, here value
     // to extract a String that I want to display
     if (value != null) {
        SimpleTnWrapper simpleTn = (SimpleTnWrapper) value;
        String displayString = simpleTn.getImgHref().getImgHref();
        displayString = displayString.substring(displayString.lastIndexOf("/") + 1);

        value = displayString;  // change the value parameter to the String ******
     }
     return super.getListCellRendererComponent(list, value, index,
           isSelected, cellHasFocus);
  }      
}

They are declared like so:

private ListCellRenderer imgRenderer = new ImgListCellRenderer();
private ListCellRenderer nonImgRenderer = new NonImgCellRenderer();

And I use them thusly:

  imgList.setCellRenderer(imgRenderer);

The DefaultListCellRenderer is pretty powerful and knows how to display a String or an ImageIcon correctly (since it is based off of a JLabel).