Java Swing

Icons

Swing introduces the concept of an icon for use in a variety of components. The Icon interface and ImageIcon class make dealing with simple images extremely easy.

The Icon Interface

The Icon interface is very simple, specifying just three methods used to determine the size of the Icon and to display it. Implementors of this interface are free to store and display the image in any way, providing a great deal of flexibility. In other words, icons don’t have to be bitmaps or GIF images, but are free to render themselves any way they choose; as we’ll see later, an icon can simply draw on the component if that’s more efficient. The examples at the end of this section show a couple of different ways the interface might be implemented.

Properties

The Icon interface defines the properties listed in Table 4.3. The iconHeight and iconWidth properties specify the size of the Icon in pixels.

Table 4-3. Icon Properties

Property	Data Type	get	is	set	bound	Default Value
iconHeight	int	•
iconWidth	int	•

Method

public abstract void paintIcon(Component c, Graphics g, int x, int y)

Paints the Icon at the specified location on the given Graphics. The Component is provided to allow its properties (such as foreground or background color) to be used when painting, or to allow the component to be used as an image observer (see Section 4.2.2, later in this chapter).

Implementing Your Own Icons

Here’s a class that implements the Icon interface and uses ovals as simple ...