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

494 Chapter 13 Graphics
This method returns the font metrics of the current font.
You can use the following instance methods in the FontMetrics class to obtain the attributes
of a font and the width of a string when it is drawn using the font:
public int getAscent() // Return the ascent
public int getDescent() // Return the descent
public int getLeading() // Return the leading
public int getHeight() // Return the height
public int stringWidth(String str) // Return the width of the string
Listing 13.6 gives an example that displays a message in the center of the panel, as shown in
Figure 13.17.
create a message panel
add a message panel
set background
set font
override paintComponent
get FontMetrics
LISTING 13.6
TestCenterMessage.java
1 import javax.swing.*;
2 import java.awt.*;
3
4 public class TestCenterMessage extends JFrame {
5 public TestCenterMessage() {
6 CenterMessage messagePanel = new CenterMessage();
7 add(messagePanel);
8 messagePanel.setBackground(Color.WHITE);
9 messagePanel.setFont(new Font("Californian FB", Font.BOLD, 30));
10 }
11
12 /** Main method */
13 public static void main(String[] args) {
14 TestCenterMessage frame = new TestCenterMessage();
15 frame.setSize(300, 150);
16 frame.setTitle("CenterMessage");
17 frame.setLocationRelativeTo(null); // Center the frame
18 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
19 frame.setVisible(true);
20 }
21 }
22
23 class CenterMessage extends JPanel {
24 @Override /** Paint the message */
25 protected void paintComponent(Graphics g) {
26 super.paintComponent(g);
27
28 // Get font metrics for the current font
29 FontMetrics fm = g.getFontMetrics();
30
31 // Find the center location to display
32 int stringWidth = fm.stringWidth("Welcome to Java") ;
33 int stringAscent = fm.getAscent() ;
34
35 // Get the position of the leftmost character in the baseline
36 int xCoordinate = getWidth() / 2 - stringWidth / 2;
37 int yCoordinate = getHeight() / 2 + stringAscent / 2;
38
39 g.drawString("Welcome to Java", xCoordinate, yCoordinate);
40 }
41 }