Java 天地·Core Java·Lecture Notes·Unit 09 - Graphics- content

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‘Graphics’ class

A Graphics object has two important functions:

To store the current graphics context (see later this unit)
To provide primitive (basic) drawing methods.

Any AWT object can call getGraphics() to get a Graphics object. A Graphics object is passed to the paint() method.

The Graphics class is very important in applications that draw graphical figures. It contains a large number of methods for drawing lines, shapes, text, and images. In addition, a Graphics object stores the current graphics context (described later in this unit).

The most common way of using a Graphics object — one that you have seen already — is to use the method paint() in an applet. The Java system automatically provides a Graphics object to this method. The program can call any of the methods in the object to do whatever drawing it needs. The paint() method is normally defined like this:

public void paint (Graphics g)
{
// drawing statements go here…
}

We don't have to call the object g (in fact, this is a rather meaningless name), but it has become conventional to do so.

You will already have seen at least one method in the Graphics class: the drawString() method. This displays a String of text at a specific position.

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