Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

682 Chapter 18 Applets and Multimedia
52
53 // Invoke applet's init method
54
55
applet.init();
applet.start();
56
57 // Display the frame
58 frame.setSize(300, 300);
59 frame.setLocationRelativeTo(null); // Center the frame
60 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
61 frame.setVisible(true);
62 }
63
64 /** Get command-line parameters */
65 private void getCommandLineParameters(String[] args) {
66 // Check usage and get x, y and message
67 if (args.length != 3) {
68 System.out.println(
69 "Usage: java DisplayMessageApp x y message");
70 System.exit(1);
71 }
72 else {
73 x = Integer.parseInt(args[0]);
74 y = Integer.parseInt(args[1]);
75 message = args[2];
76 }
77 }
78 }
When you run the program as an applet, the main method is ignored. When you run it as an
application, the main method is invoked. Sample runs of the program as an application and as
an applet are shown in Figure 18.7.
(a)
FIGURE 18.7 The DisplayMessageApp class can run as an applet in (a) and as an
application in (b).
The main method creates a JFrame object frame and creates a JApplet object applet,
then places the applet applet into the frame frame and invokes its init method. The application
runs just like an applet.
The main method sets isStandalone as true (line 45) so that it does not attempt to
retrieve HTML parameters when the init method is invoked.
The setVisible(true) method (line 61) is invoked after the components are added to
the applet, and the applet is added to the frame to ensure that the components will be visible.
Otherwise, the components are not shown when the frame starts.
(b)
omitting main method
✓Point✓ Check
Important Pedagogical Note
From now on, all the GUI examples will be created as applets with a main method.
Thus, you will be able to run the program either as an applet or as an application. For
brevity, the main method is not listed in the text.
18.12 How do you pass parameters to an applet?
18.13 Where is the getParameter method defined?