drawingprogram.java~

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

// This program demonstrates the use of the listener interface, and its use 
// with gui components.  This version includes buttons.
public class DrawingProgram extends WindowController implements ItemListener, 
                                                                ActionListener{
        // Width of border around drawing area
        private static final int BORDER_X = 10;
        private static final int BORDER_Y = 10;

        // Default size when we create a new shape
        private static final int DEFAULT_SIZE = 50;

        // Initial Location of shapes to be drawn
        private Location defaultLocation;

        // Buttons determining which kind of object is drawn
        private JButton framedSquareButton, framedCircleButton, filledSquareButton;

        // The menu determining which color the object should be
        private JComboBox colorMenu;

        // boundary of area drawing in
        private FramedRect drawingArea;

        // The variable to hold the last shape created
        private DrawableInterface newShape;

        // Used to support the usual dragging algorithm
        private boolean dragging;
        private Location lastMouse;

        /* 
         * Draws the program with the buttons and a blank drawing area
         */
        public void begin() {
                // Create buttons for selecting figures
                framedSquareButton = new JButton("FramedSquare");
                framedCircleButton = new JButton("FramedCircle");
                filledSquareButton = new JButton("FilledSquare");

                framedSquareButton.addActionListener(this);
                framedCircleButton.addActionListener(this);
                filledSquareButton.addActionListener(this);

                // create menu for selecting colors
                colorMenu = new JComboBox();
                colorMenu.addItem("Red");
                colorMenu.addItem("Blue");
                colorMenu.addItem("Green");
                colorMenu.addItem("Yellow");

                colorMenu.addItemListener(this);

                JPanel bottomPanel = new JPanel();
                bottomPanel.setLayout(new GridLayout(2, 1));
                JPanel buttonPanel = new JPanel();
                buttonPanel.add(framedSquareButton);
                buttonPanel.add(framedCircleButton);
                buttonPanel.add(filledSquareButton);
                bottomPanel.add(buttonPanel);
                bottomPanel.add(colorMenu);
                Container contentPane = getContentPane();
                contentPane.add(bottomPanel, BorderLayout.SOUTH);
                contentPane.validate();

                // Draw the drawing area
                drawingArea =
                        new FramedRect(
                                BORDER_X,
                                BORDER_Y,
                                canvas.getWidth() - 2 * BORDER_X,
                                canvas.getHeight() - 2 * BORDER_Y,
                                canvas);

                defaultLocation = new Location((canvas.getWidth() - DEFAULT_SIZE) / 2, (canvas.getHeight() - DEFAULT_SIZE) / 2);
        }

        /**
         * change newShape to color on color menu
         * Assumes newShape not null
         */
        private void setColor() {
                Object colorChoiceString = colorMenu.getSelectedItem();
                if (colorChoiceString.equals("Red")) {
                        newShape.setColor(Color.red);
                } else if (colorChoiceString.equals("Blue")) {
                        newShape.setColor(Color.blue);
                } else if (colorChoiceString.equals("Green")) {
                        newShape.setColor(Color.green);
                } else if (colorChoiceString.equals("Yellow")) {
                        newShape.setColor(Color.yellow);
                }
        }


        /* 
         * When the user clicks the button on a shape button, create that shape.
         */
        public void actionPerformed(ActionEvent evt) {
                // Determine the appropriate button pushed
                if (evt.getSource() == framedSquareButton) {
                        newShape = new FramedRect(defaultLocation, DEFAULT_SIZE, DEFAULT_SIZE, canvas);
                } else if (evt.getSource() == framedCircleButton) {
                        newShape = new FramedOval(defaultLocation, DEFAULT_SIZE, DEFAULT_SIZE, canvas);
                } else if (evt.getSource() == filledSquareButton) {
                        newShape = new FilledRect(defaultLocation, DEFAULT_SIZE, DEFAULT_SIZE, canvas);
                }
                setColor();
        }

        /**
         * Select a new color for the last object drawn
         */
        public void itemStateChanged(ItemEvent event) {
                if (newShape != null) {
                        setColor();
                }
        }

        /* 
         * Drag the shape with the mouse.  Notice that it doesn't matter what
         * kind of shape (FramedRect, FilledOval, etc.) we have.
         */
        public void onMouseDrag(Location loc) {
                if (dragging) {
                        newShape.move(loc.getX() - lastMouse.getX(), loc.getY() - lastMouse.getY());
                        lastMouse = loc;
                }
        }

        /* 
         * Start a drag
         */
        public void onMousePress(Location loc) {
                if (newShape != null && newShape.contains(loc)) {
                        dragging = true;
                        lastMouse = loc;
                }
        }

        /* 
         * Stop a drag
         */
        public void onMouseRelease(Location arg0) {
                dragging = false;
        }

}