Interface CellRenderer<T>

All Known Implementing Classes:
DefaultListCellRenderer, GenericListCellRenderer
public interface CellRenderer<T>

This class is geared to replace the ListCellRenderer in the long run to provide a more generic rendering API. 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

    Modifier and Type
    Method
    Description
    Component
    getCellRendererComponent(Component list, Object model, T value, int index, boolean isSelected)
    Returns a component instance that is already set to render "value".
    Component
    getFocusComponent(Component list)
    Returns a component instance that is painted under the currently focused renderer and is animated to provide smooth scrolling.

  • Method Details

    • getCellRendererComponent

      Component getCellRendererComponent(Component list, Object model, 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: the list component

      • model: the model behind the render

      • value: the value to render

      • index: the index in the list

      • isSelected: whether the entry is selected

      Returns

      a component to paint within the list

    • getFocusComponent

      Component getFocusComponent(Component 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: the parent list
      Returns

      a component to use as focus

      See also
      • List#setSmoothScrolling