sketchview.java

Beginning Java 2, SDK 1.4 Edition Exercise Code samples for this book

import javax.swing.JComponent;

import java.util.Observer;                  
import java.util.Observable;                  
import java.util.Iterator;

import java.awt.Graphics;
import java.awt.Graphics2D;                          
import java.awt.Point;
import java.awt.Color;
import java.awt.Rectangle;
import java.awt.Shape;

import java.awt.event.MouseEvent;    

import javax.swing.event.MouseInputAdapter;    

class SketchView extends JComponent implements Observer, Constants {
  public SketchView(Sketcher theApp) {
    this.theApp = theApp;
    MouseHandler handler = new MouseHandler();        // create the mouse listener
    addMouseListener(handler);                        // Listen for button events
    addMouseMotionListener(handler);                  // Listen for motion events

  }

  public void paint(Graphics g) {
    Graphics2D g2D = (Graphics2D)g;                // Get a Java 2D device context

    Iterator elements = theApp.getModel().getIterator();
    Element element;                                    // Stores an element

    while(elements.hasNext()) {                         // Go through the list
      element = (Element)elements.next();               // Get the next element
      g2D.setPaint(element.getColor());                 // Set the element color
      Shape shape = element.getShape();
      g2D.draw(shape);                                  // Draw its shape
      if(element.isFilled())
        g2D.fill(shape);
    }
  }

  public void update(Observable o, Object rectangle) {
    if(rectangle == null)
      repaint();
    else
      repaint((Rectangle)rectangle);
  }

  class MouseHandler extends MouseInputAdapter {
    public void mousePressed(MouseEvent e) {
    start = e.getPoint();                   // Save the cursor position in start
    if(button1Down = (e.getButton() == MouseEvent.BUTTON1)) {
      g2D = (Graphics2D)getGraphics();                 // Get graphics context
      g2D.setXORMode(getBackground());                 // Set XOR mode
      g2D.setPaint(theApp.getWindow().getElementColor());     // Set color
    }
  }

    public void mouseDragged(MouseEvent e) {
      last = e.getPoint();                               // Save cursor position

      if(button1Down) {
        if(tempElement == null) {                       // Is there an element?
          tempElement = createElement(start, last);     // No, so create one
        } else {
          g2D.draw(tempElement.getShape());             // Yes - draw to erase it
          tempElement.modify(start, last);              // Now modify it
        }
        g2D.draw(tempElement.getShape());               // and draw it
      }
    }

    public void mouseReleased(MouseEvent e) {
      if(button1Down = (e.getButton()==MouseEvent.BUTTON1)) {
        button1Down = false;                    // Reset the button 1 flag
        if(tempElement != null) {
          theApp.getModel().add(tempElement);   // Add element to the model
          tempElement = null;                   // No temporary now stored
        }
        if(g2D != null) {                       // If there's a graphics context
          g2D.dispose();                        // ...release the resource
          g2D = null;                           // Set field to null
        }
        start = last = null;                    // Remove the points
      }
    }

    private Element createElement(Point start, Point end) {
      switch(theApp.getWindow().getElementType()) {
        case LINE:
           return new Element.Line(start, end,
                                  theApp.getWindow().getElementColor());   
        case RECTANGLE:
           return new Element.Rectangle(start, end,
                                        theApp.getWindow().getElementColor(),
                                        theApp.getWindow().isFillOn());
        
        case CIRCLE:
           return new Element.Circle(start, end, 
                                     theApp.getWindow().getElementColor(),
                                     theApp.getWindow().isFillOn());

        case CURVE:
         return new Element.Curve(start, end,
                                  theApp.getWindow().getElementColor());
        case ELLIPSE:
         return new Element.Ellipse(start, end,
                                  theApp.getWindow().getElementColor(),
                                  theApp.getWindow().isFillOn());
        default:
          assert false;                     // We should never get to here
     }
      return null;
    }

    private Point start;                     // Stores cursor position on press
    private Point last;                      // Stores cursor position on drag
    private Element tempElement;             // Stores a temporary element

    private boolean button1Down = false;          // Flag for button 1 state
    private Graphics2D g2D = null;                   // Temporary graphics context
  }


  private Sketcher theApp;           // The application object
}