Java know how much (95) Drawing basics

To display text and drawings on a plane, you first determine a planar coordinate system. The Java language Convention, where a rectangular area on the display is the program drawing area, the coordinate origin (0,0) is located in the upper-left corner of the entire area. A coordinate point (x, y) corresponds to a pixel in the screen window, which is an integer. As shown in 12.1. The window size is specified by the width and height of the hypertext file. For example, the following hypertext determines that the window is 250 pixels wide and 400 pixels high:
<applet code = H.class width=250 height=400></applet>
Note: The applet is a Java applet that embeds Web pages and is no longer explained in this tutorial because it is rarely used at this time, and is only a sample reference.

Figure 12.1

Basic functions of the Raphics class
In the java.awt package, class graphics provides the ability to create fonts, set display colors, display images and text, and draw and fill various geometries. You can get a graphics object from a graphical object or by using the Getgraphics () method of component. The Graphics2D class inherits the graphics class and adds many state properties, allowing the application to draw more colorful graphics.

To draw in a component, you should generally override the paint () method for the subclass to which the component belongs, drawing in the overridden method. However, you want to draw in the JComponent subclass. For example, an inheritance defines a text area subclass that, in order to draw in such a text area sub-object, should rewrite Paintcomponent () to the text area subclass. The system automatically provides graphical objects to the program and passes the parameter G to the paint () method and the Paintcomponent () method.

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