com.sun.dtv.lwuit.list
Interface ListCellRenderer

All Known Implementing Classes:

DefaultListCellRenderer

public interface ListCellRenderer

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.

An instance of a renderer can be developed as such:

public class MyYesNoRenderer extends Label implements ListCellRenderer {
    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) {
        Label label = new label("");
        label.getStyle().setBgTransparency(100);
        return label;
    }
}
 

It is recommended that the component whose values are manipulated would not support features such as repaint(). This is accomplished by overriding repaint in the subclass with an empty implementation. This is advised for performance reasons, otherwise every change made to the component might trigger a repaint that wouldn't do anything but still cost in terms of processing.

Method Summary

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

Method Detail

getListCellRendererComponent

Component getListCellRendererComponent(List list,
                                       Object value,
                                       int index,
                                       boolean isSelected)

Returns a component instance that is already set to render "value". While it is not a requirement many renderers 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 - the List object

value - an Object

index - the index

isSelected - indicating whether the Component is selected

Returns:

a Component object

getListFocusComponent

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/bellow 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 - the list

Returns:

a component instance that is painted under the currently focused renderer and is animated to provide smooth scrolling.

See Also:

Component.setSmoothScrolling(boolean)