Adding a MouseListener to a panel

Question

I am trying to add the mouse actions to my panel. This is what the program is supposed to do:

Write a program that allows the user to specify a triangle

Answer 1

cam, given what you're doing, I hopped on my "work machine" and grabbed this code. It draws a rectangle on top of an image, and the rectangle only shows up after you release the mouse (it's a work in progress, unpaid, done in my spare time for stuff my employer might like). But since you're looking ahead to drawing, etc., here it is.

Uses a JDialog because I wanted it to be modal; don't let that bother you.

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

import javax.swing.GroupLayout;
import javax.swing.JDialog;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.WindowConstants;

public class RectSelectGUI extends JDialog implements MouseListener, ActionListener, WindowListener {
                private static final long serialVersionUID = 1L;
                public int overheadWd;
                public int overheadHt;
                public ImageJPanel imagePanel;
                private JMenu jMenuSelection;
                private JMenuBar jMenuBar1;
                private Dimension mouseDownLoc;
                private String errorString;

                public RectSelectGUI(String imgFileName) {
                                initComponents(imgFileName);
                }

                private void initComponents(String imgFileName) {

                                imagePanel = new ImageJPanel(imgFileName);
                                jMenuBar1 = new JMenuBar();
                                jMenuSelection = new JMenu();
        JMenuItem jMenuItemSave = new JMenuItem();
        jMenuItemSave.setActionCommand("Save");
        jMenuItemSave.addActionListener(this);
        jMenuItemSave.setText("Save");
        jMenuSelection.add(jMenuItemSave);
        JMenuItem jMenuItemCancel = new JMenuItem();
        jMenuItemCancel.setActionCommand("Cancel");
        jMenuItemCancel.addActionListener(this);
        jMenuItemCancel.setText("Cancel");
        jMenuSelection.add(jMenuItemCancel);

                                mouseDownLoc = new Dimension();
                                errorString = "No selection";

                                imagePanel.addMouseListener(this);

                                this.setModal(true);
                                this.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
                                this.addWindowListener(this);

                                GroupLayout jPanel1Layout = new GroupLayout(imagePanel);
                                imagePanel.setLayout(jPanel1Layout);
                                jPanel1Layout.setHorizontalGroup(
                                                                jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING).addGap(0, 524, Short.MAX_VALUE));
                                jPanel1Layout.setVerticalGroup(
                                                                jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING).addGap(0, 370, Short.MAX_VALUE));

                                jMenuSelection.setText("Selection");
                                jMenuBar1.add(jMenuSelection);

                                setJMenuBar(jMenuBar1);

                                GroupLayout layout = new GroupLayout(getContentPane());
                                getContentPane().setLayout(layout);
                                layout.setHorizontalGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                                                                .addGroup(layout.createSequentialGroup().addContainerGap()
                                                                                                .addComponent(imagePanel, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                                                                                .addContainerGap()));
                                layout.setVerticalGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                                                                .addGroup(layout.createSequentialGroup().addContainerGap()
                                                                                                .addComponent(imagePanel, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                                                                                .addContainerGap()));

                                pack();

                                overheadWd = this.getWidth() - imagePanel.getWidth();
                                overheadHt = this.getHeight() - imagePanel.getHeight();

                }

                public String getSelectionString() {
                                if (errorString.isEmpty()) {
                                                double rectWd = (double) imagePanel.rectWd;
                                                double rectHt = (double) imagePanel.rectHt;
                                                double rectX = (double) imagePanel.rectX;
                                                double rectY = (double) imagePanel.rectY;
                                                if (Math.abs(RectSelect.displayFactor - 1.0) > 0.001) {
                                                                System.out.println("Adjusting by displayFactor (" + RectSelect.displayFactor + ")");
                                                                rectWd /= RectSelect.displayFactor;
                                                                rectHt /= RectSelect.displayFactor;
                                                                rectX /= RectSelect.displayFactor;
                                                                rectY /= RectSelect.displayFactor;
                                                }
                                                return Math.round(rectWd) + "x" + Math.round(rectHt) + "+" + Math.round(rectX) + "+" + Math.round(rectY);
                                } else {
                                                return "ERROR: " + errorString;
                                }
                }


                @Override
                public void mouseClicked(MouseEvent e) {
                                // TODO Auto-generated method stub

                }

                @Override
                public void mousePressed(MouseEvent evt) {
                                mouseDownLoc.setSize(evt.getX(), evt.getY());
                }

                @Override
                public void mouseReleased(MouseEvent evt) {
                                Dimension mouseUpLoc = new Dimension(evt.getX(), evt.getY());
                                if (mouseDownLoc.width < mouseUpLoc.width) {
                                                imagePanel.rectX = mouseDownLoc.width;
                                                imagePanel.rectWd = mouseUpLoc.width - mouseDownLoc.width;
                                } else {
                                                imagePanel.rectX = mouseUpLoc.width;
                                                imagePanel.rectWd = mouseDownLoc.width - mouseUpLoc.width;
                                }
                                if (mouseDownLoc.height < mouseUpLoc.height) {
                                                imagePanel.rectY = mouseDownLoc.height;
                                                imagePanel.rectHt = mouseUpLoc.height - mouseDownLoc.height;
                                } else {
                                                imagePanel.rectY = mouseUpLoc.height;
                                                imagePanel.rectHt = mouseDownLoc.height - mouseUpLoc.height;
                                }
                                imagePanel.haveNewRect = true;
                                imagePanel.repaint();
                                errorString = "";
                }

                @Override
                public void actionPerformed(ActionEvent evt) {
                                String cmd = evt.getActionCommand();
                                switch (cmd) {
                                case "Save":
                                                break;
                                case "Cancel":
                                                errorString = "Cancelled";
                                                break;
                                default:
                                                System.out.println("Unknown action command " + cmd);
                                }
                                this.setVisible(false);
                }

                @Override
                public void windowClosing(WindowEvent e) {
                                errorString = "Cancelled";
                                this.setVisible(false);
                }

                @Override
                public void mouseEntered(MouseEvent e) {
                                // TODO Auto-generated method stub

                }

                @Override
                public void mouseExited(MouseEvent e) {
                                // TODO Auto-generated method stub

                }

                @Override
                public void windowOpened(WindowEvent e) {
                                try {
                                                Thread.sleep(100);
                                } catch (InterruptedException e1) {
                                }
                                this.repaint();
                }

                @Override
                public void windowClosed(WindowEvent e) {
                                // TODO Auto-generated method stub

                }

                @Override
                public void windowIconified(WindowEvent e) {
                                // TODO Auto-generated method stub

                }

                @Override
                public void windowDeiconified(WindowEvent e) {
                                // TODO Auto-generated method stub

                }

                @Override
                public void windowActivated(WindowEvent e) {
                }

                @Override
                public void windowDeactivated(WindowEvent e) {
                                // TODO Auto-generated method stub

                }

}


import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import javax.swing.JPanel;

public class ImageJPanel extends JPanel {
                private static final long serialVersionUID = 1L;
                public Image localImage;
                private int origWd;
                private int origHt;
                private int displayWd;
                private int displayHt;
                public int rectX;
                public int rectY;
                public int rectWd;
                public int rectHt;
                public boolean haveNewRect;
                private Toolkit toolkit;

                ImageJPanel(String imageFileName) {
                                toolkit = Toolkit.getDefaultToolkit();
                                localImage = toolkit.getImage(imageFileName);
                }

                protected void paintComponent(Graphics g1D) {
                                Graphics2D g;
                                g = (Graphics2D) g1D;
                                // Draw the image using the Graphics object provided
                                g.drawImage(localImage, 0, 0, getDisplayWd(), getDisplayHt(), null);
                                /*
                                * Optional label.
                                Font font = new Font("SansSerif", Font.BOLD, 24);
                                g1D.setFont(font);
                                FontMetrics metrics = g1D.getFontMetrics();
                                int ht = metrics.getHeight();
                                int wd = metrics.stringWidth(this.imageFileName);
                                g.setColor(Color.LIGHT_GRAY);
                                g.fillRect(this.getWidth() - wd - 10, this.getHeight() - ht, wd + 10, ht);
                                g1D.setColor(new Color(55, 11, 160));
                                g1D.drawString(this.imageFileName, this.getWidth() - wd - 10, this.getHeight() - ht + 20);
                    */

                                // Draw a selection rectangle if requested.
                                if (haveNewRect) {
                                                g.drawRect(rectX, rectY, rectWd, rectHt);
                                                haveNewRect = false;
                                }
                }

                public int getDisplayWd() {
                                return displayWd;
                }

                public void setDisplayWd(int displayWd) {
                                this.displayWd = displayWd;
                }

                public int getDisplayHt() {
                                return displayHt;
                }

                public void setDisplayHt(int displayHt) {
                                this.displayHt = displayHt;
                }

                public int getOrigWd() {
                                return origWd;
                }

                public void setOrigWd(int origWd) {
                                this.origWd = origWd;
                }

                public int getOrigHt() {
                                return origHt;
                }

                public void setOrigHt(int origHt) {
                                this.origHt = origHt;
                }

}