public interface ListCellRenderer<T>

Known subtypesDefaultListCellRenderer, GenericListCellRenderer

A “rubber stamp” tool that allows us to extract a component (often the same component instance for all invocations) that is initialized to the value of the current item extracted from the model, this component is drawn on the list and discarded. No state of the component is kept and the component is essentially discarded.

This is a very advanced interface it is recommended that you use either the DefaultListCellRenderer or GenericListCellRenderer whenever possible to avoid mistakes.

An instance of a renderer can be developed as such:

class MyYesNoRenderer extends Label implements ListCellRenderer {
    Label label = new Label(" ");
    public Component getListCellRendererComponent(List list, Object value, int index, boolean isSelected) {
        if( ((Boolean)value).booleanValue() ) {
            setText("Yes");
        } else {
            setText("No");
        }
        return this;
    }
    public Component getListFocusComponent(List list) {
        return label;
    }
}
Form f = new Form("ListRenderer", new BorderLayout());
List lst = new List(Boolean.TRUE, Boolean.FALSE);
f.addComponent(BorderLayout.CENTER, lst);
f.show();

Methods

public abstract Component getListCellRendererComponent(List list, T value, int index, boolean isSelected)Returns a component instance that is already set to render “value”.
public abstract Component getListFocusComponent(List list)Returns a component instance that is painted under the currently focused renderer and is animated to provide smooth scrolling.

Method details

getListCellRendererComponent

public abstract Component getListCellRendererComponent(List list, T value, int index, boolean isSelected)
Returns a component instance that is already set to render “value”. While it is not a requirement many renderes often derive from a component (such as a label) and return “this”. Notice that a null value for the value argument might be sent when refreshing the theme of the list.

Parameters

list List
the list component
value T
the value to render
index int
the index in the list
isSelected boolean
whether the entry is selected

Returns

a component to paint within the list

getListFocusComponent

public abstract Component getListFocusComponent(List list)
Returns a component instance that is painted under the currently focused renderer and is animated to provide smooth scrolling. When the selection moves, this component is drawn above/below the list items - it is recommended to give this component some level of transparency (see above code example). This method is optional, an implementation can choose to return null.

Parameters

list List
the parent list

Returns

a component to use as focus

See also