ScrollDemo2.java

/*
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 * modification, are permitted provided that the following conditions
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 *
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 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package javademo.swing.scroll.ScrollDemo2;

/*
 * This code is based on an example provided by John Vella,
 * a tutorial reader.
 */

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Vector;

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;

/* ScrollDemo2.java requires no other files. */
@SuppressWarnings("serial")
public class ScrollDemo2 extends JPanel implements MouseListener
{
    private Dimension area; // indicates area taken up by graphics
    
    private Vector<Rectangle> circles; // coordinates used to draw graphics
    
    private JPanel drawingPane;
    
    private final Color colors[] = { Color.red, Color.blue, Color.green, Color.orange, Color.cyan, Color.magenta,
            Color.darkGray, Color.yellow };
    
    private final int color_n = colors.length;
    
    public ScrollDemo2()
    {
        super(new BorderLayout());
        
        area = new Dimension(0, 0);
        circles = new Vector<Rectangle>();
        
        // Set up the instructions.
        JLabel instructionsLeft = new JLabel("Click left mouse button to place a circle.");
        JLabel instructionsRight = new JLabel("Click right mouse button to clear drawing area.");
        JPanel instructionPanel = new JPanel(new GridLayout(0, 1));
        instructionPanel.setFocusable(true);
        instructionPanel.add(instructionsLeft);
        instructionPanel.add(instructionsRight);
        
        // Set up the drawing area.
        drawingPane = new DrawingPane();
        drawingPane.setBackground(Color.white);
        drawingPane.addMouseListener(this);
        
        // Put the drawing area in a scroll pane.
        JScrollPane scroller = new JScrollPane(drawingPane);
        scroller.setPreferredSize(new Dimension(200, 200));
        
        // Lay out this demo.
        add(instructionPanel, BorderLayout.PAGE_START);
        add(scroller, BorderLayout.CENTER);
    }
    
    /** The component inside the scroll pane. */
    public class DrawingPane extends JPanel
    {
        protected void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            
            Rectangle rect;
            for (int i = 0; i < circles.size(); i++)
            {
                rect = circles.elementAt(i);
                g.setColor(colors[(i % color_n)]);
                g.fillOval(rect.x, rect.y, rect.width, rect.height);
            }
        }
    }
    
    // Handle mouse events.
    public void mouseReleased(MouseEvent e)
    {
        final int W = 100;
        final int H = 100;
        boolean changed = false;
        if (SwingUtilities.isRightMouseButton(e))
        {
            // This will clear the graphic objects.
            circles.removeAllElements();
            area.width = 0;
            area.height = 0;
            changed = true;
        }
        else
        {
            int x = e.getX() - W / 2;
            int y = e.getY() - H / 2;
            if (x < 0)
                x = 0;
            if (y < 0)
                y = 0;
            Rectangle rect = new Rectangle(x, y, W, H);
            circles.addElement(rect);
            drawingPane.scrollRectToVisible(rect);
            
            int this_width = (x + W + 2);
            if (this_width > area.width)
            {
                area.width = this_width;
                changed = true;
            }
            
            int this_height = (y + H + 2);
            if (this_height > area.height)
            {
                area.height = this_height;
                changed = true;
            }
        }
        if (changed)
        {
            // Update client's preferred size because
            // the area taken up by the graphics has
            // gotten larger or smaller (if cleared).
            drawingPane.setPreferredSize(area);
            
            // Let the scroll pane know to update itself
            // and its scrollbars.
            drawingPane.revalidate();
        }
        drawingPane.repaint();
    }
    
    public void mouseClicked(MouseEvent e)
    {
    }
    
    public void mouseEntered(MouseEvent e)
    {
    }
    
    public void mouseExited(MouseEvent e)
    {
    }
    
    public void mousePressed(MouseEvent e)
    {
    }
    
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI()
    {
        // Create and set up the window.
        JFrame frame = new JFrame("ScrollDemo2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        // Create and set up the content pane.
        JComponent newContentPane = new ScrollDemo2();
        newContentPane.setOpaque(true); // content panes must be opaque
        frame.setContentPane(newContentPane);
        
        // Display the window.
        frame.pack();
        frame.setVisible(true);
    }
    
    public static void main(String[] args)
    {
        // Schedule a job for the event-dispatching thread:
        // creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowGUI();
            }
        });
    }
}