PointExample.java Source code

Introduction

Here is the source code for PointExample.java

Source

//Send questions, comments, bug reports, etc. to the authors:

//Rob Warner (rwarner@interspatial.com)
//Robert Harris (rbrt_harris@yahoo.com)

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.*;

/**
 * This class demonstrates drawing points. It draws a sine wave.
 */
public class PointExample {
    /**
     * Runs the application
     */
    public void run() {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Point Example");
        createContents(shell);
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }

    /**
     * Creates the main window's contents
     * 
     * @param shell the main window
     */
    private void createContents(Shell shell) {
        shell.setLayout(new FillLayout());

        // Create the canvas for drawing on
        Canvas canvas = new Canvas(shell, SWT.NONE);

        // Add the paint handler to draw the sine wave
        canvas.addPaintListener(new PointExamplePaintListener());

        // Use a white background
        canvas.setBackground(shell.getDisplay().getSystemColor(SWT.COLOR_WHITE));
    }

    /**
     * This class draws a sine wave using points
     */
    private class PointExamplePaintListener implements PaintListener {
        public void paintControl(PaintEvent e) {
            // Get the canvas and its dimensions
            Canvas canvas = (Canvas) e.widget;
            int maxX = canvas.getSize().x;
            int maxY = canvas.getSize().y;

            // Calculate the middle
            int halfX = (int) maxX / 2;
            int halfY = (int) maxY / 2;

            // Set the line color and draw a horizontal axis
            e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_BLACK));
            e.gc.drawLine(0, halfY, maxX, halfY);

            // Draw the sine wave
            for (int i = 0; i < maxX; i++) {
                e.gc.drawPoint(i, getNormalizedSine(i, halfY, maxX));
            }
        }

        /**
         * Calculates the sine value
         * 
         * @param x the value along the x-axis
         * @param halfY the value of the y-axis
         * @param maxX the width of the x-axis
         * @return int
         */
        int getNormalizedSine(int x, int halfY, int maxX) {
            double piDouble = 2 * Math.PI;
            double factor = piDouble / maxX;
            return (int) (Math.sin(x * factor) * halfY + halfY);
        }
    }

    /**
     * The application entry point
     * 
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        new PointExample().run();
    }
}