centermessage.java

JAVA程序设计导论那本书上的一些源代码. 在学那本书的下来的

import javax.swing.*;
import java.awt.*;

public class CenterMessage extends JPanel {
  /** Main method */
  public static void main(String[] args) {
    JFrame frame = new JFrame("CenterMessage");
    CenterMessage m = new CenterMessage();
    m.setBackground(Color.white);
    m.setFont(new Font("Californian FB", Font.BOLD, 30));
    frame.getContentPane().add(m);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(300, 200);
    frame.setVisible(true);
  }

  /** Paint the message */
  protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    // Get font metrics for the current font
    FontMetrics fm = g.getFontMetrics();

    // Find the center location to display
    int stringWidth = fm.stringWidth("Welcome to Java");
    int stringAscent = fm.getAscent();

    // Get the position of the leftmost character in the baseline
    int xCoordinate = getWidth() / 2 - stringWidth / 2;
    int yCoordinate = getHeight() / 2 + stringAscent / 2;

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