Java Swing: Set member which is displayed in JListBox

Question

Is there a comparable mechanism to the .NET "set DisplayMember" for the JListBox Swing component?

Overriding the toString() method is not sufficient because I also want to be able to change the display member at runtime.

I also looked into implementing my own ListCellRenderer, but found it not very convenient.

Ist there a easier or more elegant approach?

Thanks for your time.

Answer 1

I came up with a satisfying solution based on implementing a custom ListCellRenderer.

import java.awt.Component;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JList;
import javax.swing.ListCellRenderer;

public class DynamicCellRenderer implements ListCellRenderer {
    private final ListCellRenderer listCellRenderer;
    private String displayMember;

    public DynamicCellRenderer(String displayMember) {
        this(displayMember, new DefaultListCellRenderer());
    }

    public DynamicCellRenderer(String displayMember, ListCellRenderer wrapped) {
        listCellRenderer = wrapped;
        this.displayMember = displayMember;
    }

    @Override
    public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
        Object displayMemberValue = getDisplayMemberValue(value);
        return listCellRenderer.getListCellRendererComponent(list, displayMemberValue, index, isSelected, cellHasFocus);
    }

    private Object getDisplayMemberValue(Object value) {
        // value is the domain class
        // only works if display member is a method, TODO: fallback to field
        // displayMember is something like "getName" -> value.getName() gets called
        try {
            return value.getClass().getMethod(displayMember).invoke(value);
        } catch (Exception ex) {
            // if anything went wrong it is the programmers fault -> propagate exception
            throw new RuntimeException(ex);
        }
    }

    public String getDisplayMember() {
        return displayMember;
    }

    public void setDisplayMember(String displayMember) {
        this.displayMember = displayMember;
    }

}

In your client GUI code you can do something like this:

jListBox1.setCellRenderer(new DynamicCellRenderer("getName"));
...
...
// and later at some point
((DynamicCellRenderer) jListBox1.getCellRenderer()).setDisplayMember("getEmail");

Answer 2

You should create a wrapper class around your business object that overrides toString(). This way you keep your own object clean and can at runtime swap wrappers.

public class MyWrapper()
{
    private MyBusinessObject object;

    public String toString()
    {
        return object.getImportantString();
    }
}