GRAPHICS - Introduction to Java Programming - page 494

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.

L ISTING 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

create a message panel
add a message panel
set background
set font

protected void paintComponent(Graphics g) { override paintComponent

26 super .paintComponent(g);

27
28

// Get font metrics for the current font

FontMetrics fm = g.getFontMetrics();

get FontMetrics

29
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
40 }
41 }

g.drawString( "Welcome to Java" , xCoordinate, yCoordinate);