Java Tutorial/Swing Event/MouseListener

Drag and drop image

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.RepaintManager;
public class DragImage extends JComponent implements MouseMotionListener {
  static int imageWidth = 60, imageHeight = 60;
  int imageX, imageY;
  Image image;
  public DragImage(Image i) {
    image = i;
    addMouseMotionListener(this);
  }
  public void mouseDragged(MouseEvent e) {
    imageX = e.getX();
    imageY = e.getY();
    repaint();
  }
  public void mouseMoved(MouseEvent e) {
  }
  public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    g2.drawImage(image, imageX, imageY, this);
  }
  public static void main(String[] args) {
    String imageFile = "A.jpg";
    // Turn off double buffering
    RepaintManager.currentManager(null).setDoubleBufferingEnabled(false);
    Image image = Toolkit.getDefaultToolkit().getImage(DragImage.class.getResource(imageFile));
    image = image.getScaledInstance(imageWidth, imageHeight, Image.SCALE_DEFAULT);
    JFrame frame = new JFrame("DragImage");
    frame.getContentPane().add(new DragImage(image));
    frame.setSize(300, 300);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
  }
}

MouseListener and MouseEvent

/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     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 Sun Microsystems nor 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
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*
 * MouseEventDemo.java
 */
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class MouseEventDemo extends JPanel implements MouseListener {
  BlankArea blankArea;
  JTextArea textArea;
  static final String NEWLINE = System.getProperty("line.separator");
  public static void main(String[] args) {
    /* Use an appropriate Look and Feel */
    try {
      // UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
      // UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
      UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    } catch (UnsupportedLookAndFeelException ex) {
      ex.printStackTrace();
    } catch (IllegalAccessException ex) {
      ex.printStackTrace();
    } catch (InstantiationException ex) {
      ex.printStackTrace();
    } catch (ClassNotFoundException ex) {
      ex.printStackTrace();
    }
    /* Turn off metal"s use of bold fonts */
    UIManager.put("swing.boldMetal", Boolean.FALSE);
    // Schedule a job for the event dispatch thread:
    // creating and showing this application"s GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        createAndShowGUI();
      }
    });
  }
  /**
   * Create the GUI and show it. For thread safety, this method should be
   * invoked from the event dispatch thread.
   */
  private static void createAndShowGUI() {
    // Create and set up the window.
    JFrame frame = new JFrame("MouseEventDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    // Create and set up the content pane.
    JComponent newContentPane = new MouseEventDemo();
    newContentPane.setOpaque(true); // content panes must be opaque
    frame.setContentPane(newContentPane);
    // Display the window.
    frame.pack();
    frame.setVisible(true);
  }
  public MouseEventDemo() {
    super(new GridLayout(0, 1));
    blankArea = new BlankArea(Color.YELLOW);
    add(blankArea);
    textArea = new JTextArea();
    textArea.setEditable(false);
    JScrollPane scrollPane = new JScrollPane(textArea);
    scrollPane
        .setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
    scrollPane.setPreferredSize(new Dimension(200, 75));
    add(scrollPane);
    // Register for mouse events on blankArea and the panel.
    blankArea.addMouseListener(this);
    addMouseListener(this);
    setPreferredSize(new Dimension(450, 450));
    setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
  }
  void eventOutput(String eventDescription, MouseEvent e) {
    textArea.append(eventDescription + " detected on "
        + e.getComponent().getClass().getName() + "." + NEWLINE);
    textArea.setCaretPosition(textArea.getDocument().getLength());
  }
  public void mousePressed(MouseEvent e) {
    eventOutput("Mouse pressed (# of clicks: " + e.getClickCount() + ")", e);
  }
  public void mouseReleased(MouseEvent e) {
    eventOutput("Mouse released (# of clicks: " + e.getClickCount() + ")", e);
  }
  public void mouseEntered(MouseEvent e) {
    eventOutput("Mouse entered", e);
  }
  public void mouseExited(MouseEvent e) {
    eventOutput("Mouse exited", e);
  }
  public void mouseClicked(MouseEvent e) {
    eventOutput("Mouse clicked (# of clicks: " + e.getClickCount() + ")", e);
  }
}
/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *  - Redistributions of source code must retain the above copyright 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 Sun Microsystems nor 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 PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
class BlankArea extends JLabel {
  Dimension minSize = new Dimension(100, 50);
  public BlankArea(Color color) {
    setBackground(color);
    setOpaque(true);
    setBorder(BorderFactory.createLineBorder(Color.black));
  }
  public Dimension getMinimumSize() {
    return minSize;
  }
  public Dimension getPreferredSize() {
    return minSize;
  }
}

The MouseListener Interface

The MouseListener Interface: respond to events when the mouse cursor is moved into or out of the area occupied by a component, or one of the mouse buttons is pressed, released, or clicked.

Defined MethodsDescriptionmouseClicked(MouseEvent e)Called when a mouse button is clicked on a component - that is, when the button is pressed and releasedmousePressed(MouseEvent e)Called when a mouse button is pressed on a componentmouseReleased(MouseEvent e)Called when a mouse button is released on a componentmouseEntered(MouseEvent e)Called when the mouse enters the area occupied by a componentmouseExited(MouseEvent e)Called when the mouse exits the area occupied by a component