/* CoordinatesDemo.java requires no other files. */ import javax.swing.*; import java.awt.*; import java.awt.event.MouseEvent; import javax.swing.event.MouseInputListener; /* * This displays a framed area. As the user moves the cursor * over the area, a label displays the cursor's location. When * the user clicks, the area displays a 7x7 dot at the click * location. */ public class CoordinatesDemo { private JLabel label; private Point clickPoint, cursorPoint; private void buildUI(Container container) { container.setLayout(new BoxLayout(container, BoxLayout.PAGE_AXIS)); CoordinateArea coordinateArea = new CoordinateArea(this); container.add(coordinateArea); label = new JLabel(); resetLabel(); container.add(label); //Align the left edges of the components. coordinateArea.setAlignmentX(Component.LEFT_ALIGNMENT); label.setAlignmentX(Component.LEFT_ALIGNMENT); //redundant } public void updateCursorLocation(int x, int y) { if (x < 0 || y < 0) { cursorPoint = null; updateLabel(); return; } if (cursorPoint == null) { cursorPoint = new Point(); } cursorPoint.x = x; cursorPoint.y = y; updateLabel(); } public void updateClickPoint(Point p) { clickPoint = p; updateLabel(); } public void resetLabel() { cursorPoint = null; updateLabel(); } protected void updateLabel() { String text = ""; if ((clickPoint == null) && (cursorPoint == null)) { text = "Click or move the cursor within the framed area."; } else { if (clickPoint != null) { text += "The last click was at (" + clickPoint.x + ", " + clickPoint.y + "). "; } if (cursorPoint != null) { text += "The cursor is at (" + cursorPoint.x + ", " + cursorPoint.y + "). "; } } label.setText(text); } /** * 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("CoordinatesDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Set up the content pane. CoordinatesDemo controller = new CoordinatesDemo(); controller.buildUI(frame.getContentPane()); //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(); } }); } public static class CoordinateArea extends JComponent implements MouseInputListener { Point point = null; CoordinatesDemo controller; Dimension preferredSize = new Dimension(400,75); Color gridColor; public CoordinateArea(CoordinatesDemo controller) { this.controller = controller; //Add a border of 5 pixels at the left and bottom, //and 1 pixel at the top and right. setBorder(BorderFactory.createMatteBorder(1,5,5,1, Color.RED)); addMouseListener(this); addMouseMotionListener(this); setBackground(Color.WHITE); setOpaque(true); } public Dimension getPreferredSize() { return preferredSize; } protected void paintComponent(Graphics g) { //Paint background if we're opaque. if (isOpaque()) { g.setColor(getBackground()); g.fillRect(0, 0, getWidth(), getHeight()); } //Paint 20x20 grid. g.setColor(Color.GRAY); drawGrid(g, 20); //If user has chosen a point, paint a small dot on top. if (point != null) { g.setColor(getForeground()); g.fillRect(point.x - 3, point.y - 3, 7, 7); } } //Draws a 20x20 grid using the current color. private void drawGrid(Graphics g, int gridSpace) { Insets insets = getInsets(); int firstX = insets.left; int firstY = insets.top; int lastX = getWidth() - insets.right; int lastY = getHeight() - insets.bottom; //Draw vertical lines. int x = firstX; while (x < lastX) { g.drawLine(x, firstY, x, lastY); x += gridSpace; } //Draw horizontal lines. int y = firstY; while (y < lastY) { g.drawLine(firstX, y, lastX, y); y += gridSpace; } } //Methods required by the MouseInputListener interface. public void mouseClicked(MouseEvent e) { int x = e.getX(); int y = e.getY(); if (point == null) { point = new Point(x, y); } else { point.x = x; point.y = y; } controller.updateClickPoint(point); repaint(); } public void mouseMoved(MouseEvent e) { controller.updateCursorLocation(e.getX(), e.getY()); } public void mouseExited(MouseEvent e) { controller.resetLabel(); } public void mouseReleased(MouseEvent e) { } public void mouseEntered(MouseEvent e) { } public void mousePressed(MouseEvent e) { } public void mouseDragged(MouseEvent e) { } } }