Mega Code Archive
Extends MouseAdapter and implements MouseMotionListener to create a mouse drawing programm
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/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.awt.Cursor;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import javax.swing.JComponent;
import javax.swing.JFrame;
/**
* @version 1.32 2007-06-12
* @author Cay Horstmann
*/
public class MouseTest
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
MouseFrame frame = new MouseFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
/**
* A frame containing a panel for testing mouse operations
*/
class MouseFrame extends JFrame
{
public MouseFrame()
{
setTitle("MouseTest");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
// add component to frame
MouseComponent component = new MouseComponent();
add(component);
}
public static final int DEFAULT_WIDTH = 300;
public static final int DEFAULT_HEIGHT = 200;
}
/**
* A component with mouse operations for adding and removing squares.
*/
class MouseComponent extends JComponent
{
public MouseComponent()
{
squares = new ArrayList<Rectangle2D>();
current = null;
addMouseListener(new MouseHandler());
addMouseMotionListener(new MouseMotionHandler());
}
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
// draw all squares
for (Rectangle2D r : squares)
g2.draw(r);
}
/**
* Finds the first square containing a point.
* @param p a point
* @return the first square that contains p
*/
public Rectangle2D find(Point2D p)
{
for (Rectangle2D r : squares)
{
if (r.contains(p)) return r;
}
return null;
}
/**
* Adds a square to the collection.
* @param p the center of the square
*/
public void add(Point2D p)
{
double x = p.getX();
double y = p.getY();
current = new Rectangle2D.Double(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH,
SIDELENGTH);
squares.add(current);
repaint();
}
/**
* Removes a square from the collection.
* @param s the square to remove
*/
public void remove(Rectangle2D s)
{
if (s == null) return;
if (s == current) current = null;
squares.remove(s);
repaint();
}
private static final int SIDELENGTH = 10;
private ArrayList<Rectangle2D> squares;
private Rectangle2D current;
// the square containing the mouse cursor
private class MouseHandler extends MouseAdapter
{
public void mousePressed(MouseEvent event)
{
// add a new square if the cursor isn't inside a square
current = find(event.getPoint());
if (current == null) add(event.getPoint());
}
public void mouseClicked(MouseEvent event)
{
// remove the current square if double clicked
current = find(event.getPoint());
if (current != null && event.getClickCount() >= 2) remove(current);
}
}
private class MouseMotionHandler implements MouseMotionListener
{
public void mouseMoved(MouseEvent event)
{
// set the mouse cursor to cross hairs if it is inside
// a rectangle
if (find(event.getPoint()) == null) setCursor(Cursor.getDefaultCursor());
else setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
}
public void mouseDragged(MouseEvent event)
{
if (current != null)
{
int x = event.getX();
int y = event.getY();
// drag the current rectangle to center it at (x, y)
current.setFrame(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH, SIDELENGTH);
repaint();
}
}
}
}
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