teaching machines

CS 145 Lecture 23 – GUIs, Non-zero Gravity

April 27, 2012 by Chris Johnson. Filed under cs145, lectures, spring 2012.

Agenda

• TIOBE flip
• Swing GUI framework
• a tease of inheritance
• event-driven programming
• painting dropping circles
• composition
• collaboration graphs in SMC
• law #31: try local first

Code

DroppingCircles.java

package prefinal;

import javax.swing.JFrame;

public class DroppingCircles {
  public static void main(String[] args) {
    JFrame frame = new JFrame("Drop Circles");
    
//    frame.add(new JButton("Click me!"));
//    frame.add(new JLabel("Read me!"));
    frame.add(new DroppingCirclesCanvas());
    
    frame.setSize(512, 512);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
  }
}

DroppingCirclesCanvas.java

package prefinal;

import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JPanel;

public class DroppingCirclesCanvas extends JPanel implements MouseListener {
  private Sphere sphere;
  
  public DroppingCirclesCanvas() {
    addMouseListener(this);
  }
  
  protected void paintComponent(Graphics g) {
//    g.fillOval(50, 50, 100, 25);
    if (sphere != null) {
      sphere.draw(g);
    }
  }

  public void mouseClicked(MouseEvent e) {
    System.out.println(e.getX());
    System.out.println(e.getY());
    
    sphere = new Sphere(e.getX(), e.getY());
    repaint();
  }

  public void mouseEntered(MouseEvent arg0) {
  }

  public void mouseExited(MouseEvent arg0) {
  }

  public void mousePressed(MouseEvent arg0) {
  }

  public void mouseReleased(MouseEvent arg0) {
  }
}

Sphere.java

package prefinal;

import java.awt.Color;
import java.awt.Graphics;

public class Sphere {
  public static final int RADIUS = 25;
  
  private int centerX;
  private int centerY;

  public Sphere(int x,
                int y) {
    centerX = x;
    centerY = y;
  }

  public void draw(Graphics g) {
    g.setColor(Color.RED);
    g.fillOval(centerX - RADIUS, centerY - RADIUS, 2 * RADIUS, 2 * RADIUS);
  }
}

Haiku