package graphics;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
/**
* Class for simple graphics example. The program provides a surface on
* which the user can draw rectangles by clicking and dragging.
*
* @author B.L. Massingill
*/
public class SimpleDrawX {
/**
* Creates and displays GUI.
* (I could also have put this code in a constructor.)
*/
private static void createAndShowGUI() {
// basic GUI setup
JFrame theFrame = new JFrame("Drawing Example");
// set what should happen when window is closed
theFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// add panel that supports drawing as described
final DrawingPanel drawPanel = new DrawingPanel();
theFrame.add(drawPanel, BorderLayout.CENTER);
// add a "clear" button
JPanel buttonPanel = new JPanel(new FlowLayout());
JButton clearButton = new JButton("Clear");
clearButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
drawPanel.clear();
drawPanel.repaint();
}
});
buttonPanel.add(clearButton);
theFrame.add(buttonPanel, BorderLayout.SOUTH);
// set size
theFrame.setSize(600, 400);
// make visible
theFrame.setVisible(true);
}
/**
* Main method.
*/
public static void main(String[] args) {
// do this in the way recommended as thread-safe
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
// ---- classes ----
/**
* Class for rectangle.
*/
private static class SimpleRectangle {
public final int left;
public final int top;
public final int width;
public final int height;
public SimpleRectangle(int l, int t, int w, int h) {
left = l;
top = t;
width = w;
height = h;
}
}
/**
* Class for "drawing panel".
*/
private static class DrawingPanel extends JPanel {
/**
* Constructor.
*/
public DrawingPanel() {
// add listeners for various mouse events
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
onMousePressed(e);
}
public void mouseReleased(MouseEvent e) {
onMouseReleased(e);
}
});
addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
onMouseDragged(e);
}
});
// reset everything
clear();
}
/**
* Clear panel.
*/
public void clear() {
rectangles = new ArrayList<SimpleRectangle>();
selectedPoint = null;
dragPoint = null;
}
/**
* "Paint" panel. This is where "custom graphics" is done.
* @param g graphics context on which to perform drawing
*/
public void paintComponent(Graphics g) {
// paint background and get Graphics2D version of g
super.paintComponent(g);
// paint completed rectangles
int nextColor = 0;
for (SimpleRectangle r : rectangles) {
g.setColor(colors[nextColor]);
g.fillRect(r.left, r.top, r.width, r.height);
nextColor = (nextColor + 1) % colors.length;
}
// paint something indicating shape-in-progress
if ((selectedPoint != null) && (dragPoint != null)) {
g.setColor(Color.black);
SimpleRectangle outline =
makeRectangle(selectedPoint, dragPoint);
g.drawRect(outline.left, outline.top,
outline.width, outline.height);
}
}
/**
* Respond to "mouse pressed" event (by saving the clicked-on
* point so we can use it later to construct a rectangle).
* @param e object describing the event
*/
private void onMousePressed(MouseEvent e) {
selectedPoint = e.getPoint();
}
/**
* Respond to "mouse released" event (by constructing a rectangle
* using the point saved on a "mouse pressed" event).
* @param e object describing the event
*/
private void onMouseReleased(MouseEvent e) {
if (selectedPoint != null) {
SimpleRectangle r = makeRectangle(selectedPoint, e.getPoint());
rectangles.add(r);
selectedPoint = null;
dragPoint = null;
}
repaint();
}
/**
* Respond to "mouse dragged" event (by showing an outline of the
* rectangle that would be added if the mouse were released).
* @param e object describing the event
*/
private void onMouseDragged(MouseEvent e) {
dragPoint = e.getPoint();
repaint();
}
/**
* Construct shape using p1 and p2 as diagonally-opposite corners.
* @param p1 one point
* @param p2 the other point
* @return rectangle
*/
private SimpleRectangle makeRectangle(Point p1, Point p2) {
return new SimpleRectangle(
Math.min(p1.x, p2.x),
Math.min(p1.y, p2.y),
Math.abs(p1.x - p2.x),
Math.abs(p1.y - p2.y));
}
// ---- variables ----
// colors to cycle through
private static Color[] colors = new Color[] {
Color.yellow, Color.red, Color.blue, Color.green
};
private ArrayList<SimpleRectangle> rectangles;
private Point selectedPoint;
private Point dragPoint;
}
}