Java基础之在窗口中绘图——使用模型/视图体系结构在视图中绘图（Sketcher 1 drawing a 3D rectangle）

控制台程序。

在模型中表示数据视图的类用来显示草图并处理用户的交互操作，所以这种类把显示方法和草图控制器合并在一起。不专用于某个视图的通用GUI创建和操作在SketcherFrame类中处理。

模型对象包含构成草图的文本和图形。模型类可以称为SketcherModel，表示模型视图的类可以称为SketcherView.

应用程序对象全面负责管理程序涉及的其他对象之间的链接。只要应用程序类能使每个对象可用，可以访问应用程序对象的任何对象就都要与其他对象进行通信。因此，应用程序对象是对象之间的通信通道。

注意：SketcherFrame不是视图类，这个类仅仅定义应用程序窗口及其关联的GUI组件。创建SketcherView对象时，应把SketcherView对象插入到SketcherFrame对象的内容面板中，并使用内容面板的布局管理器进行管理。通过将视图类与应用程序类分开定义，就可以把草图的视图与用于和程序交互的菜单及其他组件分开。这么做的优点是显示草图的区域能拥有自己的坐标系统，这种坐标系统独立于应用程序窗口的坐标系统。

1、SketcherModel类：

import java.io.Serializable;
import java.util.Observable;

public class SketcherModel extends Observable implements Serializable {
  // Detail of the rest of class to be filled in later...
  private final static long serialVersionUID = 1001L;
}

这个类可以串行化，因为我们希望把草图保存到文件中。SketcherModel类扩展了Observable类，所以可以使用这个类把视图类注册为观察器，并将视图的任何变化自动通知给模型。当草图拥有多个视图时，这个功能就会很有用。

2、SketcherView类：

import javax.swing.JComponent;
import java.util.*;
import java.awt.*;

@SuppressWarnings("serial")
public class SketcherView extends JComponent implements Observer {
  public SketcherView(Sketcher theApp) {
    this.theApp = theApp;
  }

  // Method called by Observable object when it changes
  public void update(Observable o, Object rectangle) {
    // Code to respond to changes in the model...
  }

  // Method to draw on the view
  @Override
  public void paint(Graphics g) {
    // Temporary code...
    Graphics2D g2D = (Graphics2D)g;                                    // Get a Java 2D device context

    g2D.setPaint(Color.RED);                                           // Draw in red
    g2D.draw3DRect(50, 50, 150, 100, true);                            // Draw a raised 3D rectangle
    g2D.drawString("A nice 3D rectangle", 60, 100);                    // Draw some text
  }

  private Sketcher theApp;                                             // The application object
}

视图需要访问模型才能显示，但构造函数不是在视图中保存对模型的引用，而是让应用程序对象通过参数把引用传送给视图。视图对象可以使用应用程序对象来访问模型对象，如果需要，还可以访问应用程序窗口。
视图注册为模型的观察器。如果存在完全不同的对象表示模型，例如要加载新的文件，视图对象就会自动获得模型已发生改变的通知，并且能重绘视图作为响应。

3、Sketcher类：

// Sketching application
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Sketcher {
  public static void main(String[] args) {
     theApp = new Sketcher();                                          // Create the application object
   SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                          theApp.createGUI();                          // Call GUI creator
            }
        });
  }

  // Method to create the application GUI
  private void createGUI() {
    window = new SketcherFrame("Sketcher", this);                      // Create the app window
    Toolkit theKit = window.getToolkit();                              // Get the window toolkit
    Dimension wndSize = theKit.getScreenSize();                        // Get screen size

    // Set the position to screen center & size to half screen size
    window.setSize(wndSize.width/2, wndSize.height/2);                 // Set window size
    window.setLocationRelativeTo(null);                                // Center window

    window.addWindowListener(new WindowHandler());                     // Add window listener

    sketch = new SketcherModel();                                      // Create the model
    view = new SketcherView(this);                                     // Create the view
    sketch.addObserver(view);                                          // Register view with the model
    window.getContentPane().add(view, BorderLayout.CENTER);
    window.setVisible(true);
  }

  // Return a reference to the application window
  public SketcherFrame getWindow() {
     return window;
  }

  // Return a reference to the model
  public SketcherModel getModel() {
     return sketch;
  }

  // Return a reference to the view
  public SketcherView getView() {
     return view;
  }

  // Handler class for window events
  class WindowHandler extends WindowAdapter {
    // Handler for window closing event
    @Override
    public void windowClosing(WindowEvent e) {
      // Code to be added here...
    }
  }

  private SketcherModel sketch;                                        // The data model for the sketch
  private SketcherView view;                                           // The view of the sketch
  private SketcherFrame window;                                        // The application window
  private static Sketcher theApp;                                      // The application object
}

Sketcher类中的新方法返回对应用程序窗口、模型和视图的引用，所以在Sketcher应用程序代码的任何地方，只要有对应用程序对象的引用，就可以访问它们。
在Sketcher类的createGUI()方法中创建完模型和视图对象后，就把视图注册为模型的观察器，让模型在发生变化时通知视图。

4、SketcherFrame类：

// Frame for the Sketcher application
import javax.swing.*;
import javax.swing.border.*;
import java.awt.event.*;
import java.awt.*;

import static java.awt.event.InputEvent.*;
import static java.awt.AWTEvent.*;
import static java.awt.Color.*;
import static Constants.SketcherConstants.*;
import static javax.swing.Action.*;

@SuppressWarnings("serial")
public class SketcherFrame extends JFrame {
  // Constructor
  public SketcherFrame(String title, Sketcher theApp) {
    setTitle(title);                                                   // Set the window title
    this.theApp = theApp;                                              // Save app. object reference
    setJMenuBar(menuBar);                                              // Add the menu bar to the window
    setDefaultCloseOperation(EXIT_ON_CLOSE);                           // Default is exit the application

    createFileMenu();                                                  // Create the File menu
    createElementMenu();                                               // Create the element menu
    createColorMenu();                                                 // Create the element menu
    createToolbar();
    toolBar.setRollover(true);
    getContentPane().add(toolBar, BorderLayout.NORTH);
  }

  // Create File menu item actions
  private void createFileMenuActions() {
    newAction = new FileAction("New", 'N', CTRL_DOWN_MASK);
    openAction = new FileAction("Open", 'O', CTRL_DOWN_MASK);
    closeAction = new FileAction("Close");
    saveAction = new FileAction("Save", 'S', CTRL_DOWN_MASK);
    saveAsAction = new FileAction("Save As...");
    printAction = new FileAction("Print", 'P', CTRL_DOWN_MASK);
    exitAction = new FileAction("Exit", 'X', CTRL_DOWN_MASK);

    // Initialize the array
    FileAction[] actions = {openAction, closeAction, saveAction, saveAsAction, printAction, exitAction};
    fileActions = actions;

    // Add toolbar icons
    newAction.putValue(LARGE_ICON_KEY, NEW24);
    openAction.putValue(LARGE_ICON_KEY, OPEN24);
    saveAction.putValue(LARGE_ICON_KEY, SAVE24);
    saveAsAction.putValue(LARGE_ICON_KEY, SAVEAS24);
    printAction.putValue(LARGE_ICON_KEY, PRINT24);

    // Add menu item icons
    newAction.putValue(SMALL_ICON, NEW16);
    openAction.putValue(SMALL_ICON, OPEN16);
    saveAction.putValue(SMALL_ICON, SAVE16);
    saveAsAction.putValue(SMALL_ICON,SAVEAS16);
    printAction.putValue(SMALL_ICON, PRINT16);

    // Add tooltip text
    newAction.putValue(SHORT_DESCRIPTION, "Create a new sketch");
    openAction.putValue(SHORT_DESCRIPTION, "Read a sketch from a file");
    closeAction.putValue(SHORT_DESCRIPTION, "Close the current sketch");
    saveAction.putValue(SHORT_DESCRIPTION, "Save the current sketch to file");
    saveAsAction.putValue(SHORT_DESCRIPTION, "Save the current sketch to a new file");
    printAction.putValue(SHORT_DESCRIPTION, "Print the current sketch");
    exitAction.putValue(SHORT_DESCRIPTION, "Exit Sketcher");
  }

  // Create the File menu
  private void createFileMenu() {
    JMenu fileMenu = new JMenu("File");                                // Create File menu
    fileMenu.setMnemonic('F');                                         // Create shortcut
    createFileMenuActions();                                           // Create Actions for File menu item

    // Construct the file drop-down menu
    fileMenu.add(newAction);                                           // New Sketch menu item
    fileMenu.add(openAction);                                          // Open sketch menu item
    fileMenu.add(closeAction);                                         // Close sketch menu item
    fileMenu.addSeparator();                                           // Add separator
    fileMenu.add(saveAction);                                          // Save sketch to file
    fileMenu.add(saveAsAction);                                        // Save As menu item
    fileMenu.addSeparator();                                           // Add separator
    fileMenu.add(printAction);                                         // Print sketch menu item
    fileMenu.addSeparator();                                           // Add separator
    fileMenu.add(exitAction);                                          // Print sketch menu item
    menuBar.add(fileMenu);                                             // Add the file menu
  }

  // Create Element  menu actions
  private void createElementTypeActions() {
    lineAction = new TypeAction("Line", LINE, 'L', CTRL_DOWN_MASK);
    rectangleAction = new TypeAction("Rectangle", RECTANGLE, 'R', CTRL_DOWN_MASK);
    circleAction =  new TypeAction("Circle", CIRCLE,'C', CTRL_DOWN_MASK);
    curveAction = new TypeAction("Curve", CURVE,'U', CTRL_DOWN_MASK);

    // Initialize the array
    TypeAction[] actions = {lineAction, rectangleAction, circleAction, curveAction};
    typeActions = actions;

    // Add toolbar icons
    lineAction.putValue(LARGE_ICON_KEY, LINE24);
    rectangleAction.putValue(LARGE_ICON_KEY, RECTANGLE24);
    circleAction.putValue(LARGE_ICON_KEY, CIRCLE24);
    curveAction.putValue(LARGE_ICON_KEY, CURVE24);

    // Add menu item icons
    lineAction.putValue(SMALL_ICON, LINE16);
    rectangleAction.putValue(SMALL_ICON, RECTANGLE16);
    circleAction.putValue(SMALL_ICON, CIRCLE16);
    curveAction.putValue(SMALL_ICON, CURVE16);

    // Add tooltip text
    lineAction.putValue(SHORT_DESCRIPTION, "Draw lines");
    rectangleAction.putValue(SHORT_DESCRIPTION, "Draw rectangles");
    circleAction.putValue(SHORT_DESCRIPTION, "Draw circles");
    curveAction.putValue(SHORT_DESCRIPTION, "Draw curves");
  }

  // Create the Elements menu
  private void createElementMenu() {
    createElementTypeActions();
    elementMenu = new JMenu("Elements");                               // Create Elements menu
    elementMenu.setMnemonic('E');                                      // Create shortcut
    createRadioButtonDropDown(elementMenu, typeActions, lineAction);
    menuBar.add(elementMenu);                                          // Add the element menu
  }

  // Create Color menu actions
  private void createElementColorActions() {
    redAction = new ColorAction("Red", RED, 'R', CTRL_DOWN_MASK|ALT_DOWN_MASK);
    yellowAction = new ColorAction("Yellow", YELLOW, 'Y', CTRL_DOWN_MASK|ALT_DOWN_MASK);
    greenAction = new ColorAction("Green", GREEN, 'G', CTRL_DOWN_MASK|ALT_DOWN_MASK);
    blueAction = new ColorAction("Blue", BLUE, 'B', CTRL_DOWN_MASK|ALT_DOWN_MASK);

    // Initialize the array
    ColorAction[] actions = {redAction, greenAction, blueAction, yellowAction};
    colorActions = actions;

    // Add toolbar icons
    redAction.putValue(LARGE_ICON_KEY, RED24);
    greenAction.putValue(LARGE_ICON_KEY, GREEN24);
    blueAction.putValue(LARGE_ICON_KEY, BLUE24);
    yellowAction.putValue(LARGE_ICON_KEY, YELLOW24);

    // Add menu item icons
    redAction.putValue(SMALL_ICON, RED16);
    blueAction.putValue(SMALL_ICON, BLUE16);
    greenAction.putValue(SMALL_ICON, GREEN16);
    yellowAction.putValue(SMALL_ICON, YELLOW16);

    // Add tooltip text
    redAction.putValue(SHORT_DESCRIPTION, "Draw in red");
    blueAction.putValue(SHORT_DESCRIPTION, "Draw in blue");
    greenAction.putValue(SHORT_DESCRIPTION, "Draw in green");
    yellowAction.putValue(SHORT_DESCRIPTION, "Draw in yellow");
  }

  // Create the Color menu
  private void createColorMenu() {
    createElementColorActions();
    colorMenu = new JMenu("Color");                                    // Create Elements menu
    colorMenu.setMnemonic('C');                                        // Create shortcut
    createRadioButtonDropDown(colorMenu, colorActions, blueAction);
    menuBar.add(colorMenu);                                            // Add the color menu
  }

  // Menu creation helper
  private void createRadioButtonDropDown(JMenu menu, Action[] actions, Action selected) {
    ButtonGroup group = new ButtonGroup();
    JRadioButtonMenuItem item = null;
    for(Action action : actions) {
      group.add(menu.add(item = new JRadioButtonMenuItem(action)));
      if(action == selected) {
        item.setSelected(true);                                        // This is default selected
      }
    }
  }

  // Create toolbar buttons on the toolbar
  private void createToolbar() {
    for(FileAction action: fileActions){
      if(action != exitAction && action != closeAction)
        addToolbarButton(action);                                      // Add the toolbar button
    }
    toolBar.addSeparator();

    // Create Color menu buttons
    for(ColorAction action:colorActions){
        addToolbarButton(action);                                      // Add the toolbar button
    }

    toolBar.addSeparator();

    // Create Elements menu buttons
    for(TypeAction action:typeActions){
        addToolbarButton(action);                                      // Add the toolbar button
    }
 }

  // Create and add a toolbar button
  private void addToolbarButton(Action action) {
    JButton button = new JButton(action);                              // Create from Action
    button.setBorder(BorderFactory.createCompoundBorder(               // Add button border
           new EmptyBorder(2,5,5,2),                                   // Outside border
           BorderFactory.createRaisedBevelBorder()));                  // Inside border
    button.setHideActionText(true);                                    // No label on the button
    toolBar.add(button);                                               // Add the toolbar button
  }

  // Set radio button menu checks
  private void setChecks(JMenu menu, Object eventSource) {
    if(eventSource instanceof JButton){
      JButton button = (JButton)eventSource;
      Action action = button.getAction();
      for(int i = 0 ; i < menu.getItemCount() ; ++i) {
        JMenuItem item = menu.getItem(i);
        item.setSelected(item.getAction() == action);
      }
    }
  }

  // Inner class defining Action objects for File menu items
  class FileAction extends AbstractAction {
    // Create action with a name
    FileAction(String name) {
      super(name);
    }

    // Create action with a name and accelerator
    FileAction(String name, char ch, int modifiers) {
      super(name);
      putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));

      // Now find the character to underline
      int index = name.toUpperCase().indexOf(ch);
      if(index != -1) {
        putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
      }
    }

    // Event handler
    public void actionPerformed(ActionEvent e) {
      // You will add action code here eventually...
    }
  }

  // Inner class defining Action objects for Element type menu items
  class TypeAction extends AbstractAction {
    // Create action with just a name property
    TypeAction(String name, int typeID) {
      super(name);
      this.typeID = typeID;
    }

    // Create action with a name and an accelerator
    private TypeAction(String name,int typeID, char ch, int modifiers) {
      this(name, typeID);
      putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));

      // Now find the character to underline
      int index = name.toUpperCase().indexOf(ch);
      if(index != -1) {
        putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
      }
    }

    public void actionPerformed(ActionEvent e) {
      elementType = typeID;
      setChecks(elementMenu, e.getSource());
    }

    private int typeID;
  }

  // Handles color menu items
  class ColorAction  extends AbstractAction {
    // Create an action with a name and a color
    public ColorAction(String name, Color color) {
      super(name);
      this.color = color;
    }

    // Create an action with a name, a color, and an accelerator
    public ColorAction(String name, Color color, char ch, int modifiers) {
      this(name, color);
      putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));

      // Now find the character to underline
      int index = name.toUpperCase().indexOf(ch);
      if(index != -1) {
        putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
      }
    }

    public void actionPerformed(ActionEvent e) {
      elementColor = color;
      setChecks(colorMenu, e.getSource());
    }

    private Color color;
  }

  // File actions
  private FileAction newAction, openAction, closeAction, saveAction, saveAsAction, printAction, exitAction;
  private FileAction[] fileActions;                                    // File actions as an array

  // Element type actions
  private TypeAction lineAction, rectangleAction, circleAction, curveAction;
  private TypeAction[] typeActions;                                    // Type actions as an array

// Element color actions
  private ColorAction redAction, yellowAction,greenAction, blueAction;
  private ColorAction[] colorActions;                                  // Color actions as an array

  private JMenuBar menuBar = new JMenuBar();                           // Window menu bar
  private JMenu elementMenu;                                           // Elements menu
  private JMenu colorMenu;                                             // Color menu

  private Color elementColor = DEFAULT_ELEMENT_COLOR;                  // Current element color
  private int elementType = DEFAULT_ELEMENT_TYPE;                      // Current element type
  private JToolBar toolBar = new JToolBar();                           // Window toolbar
  private Sketcher theApp;                                             // The application object
}

5、自定义常量包SketcherConstants：

// Defines application wide constants
package Constants;
import java.awt.Color;
import javax.swing.*;

public class SketcherConstants {
  // Path for images
  public final static String imagePath = "E:/JavaProject/BeginningJava/Images/";

  // Toolbar icons
  public final static Icon NEW24 = new ImageIcon(imagePath + "New24.gif");
  public final static Icon OPEN24 = new ImageIcon(imagePath + "Open24.gif");
  public final static Icon SAVE24 = new ImageIcon(imagePath + "Save24.gif");
  public final static Icon SAVEAS24 = new ImageIcon(imagePath + "SaveAs24.gif");
  public final static Icon PRINT24 = new ImageIcon(imagePath + "Print24.gif");

  public final static Icon LINE24 = new ImageIcon(imagePath + "Line24.gif");
  public final static Icon RECTANGLE24 = new ImageIcon(imagePath + "Rectangle24.gif");
  public final static Icon CIRCLE24 = new ImageIcon(imagePath + "Circle24.gif");
  public final static Icon CURVE24 = new ImageIcon(imagePath + "Curve24.gif");

  public final static Icon RED24 = new ImageIcon(imagePath + "Red24.gif");
  public final static Icon GREEN24 = new ImageIcon(imagePath + "Green24.gif");
  public final static Icon BLUE24 = new ImageIcon(imagePath + "Blue24.gif");
  public final static Icon YELLOW24 = new ImageIcon(imagePath + "Yellow24.gif");

  // Menu item icons
  public final static Icon NEW16 = new ImageIcon(imagePath + "new16.gif");
  public final static Icon OPEN16 = new ImageIcon(imagePath + "Open16.gif");
  public final static Icon SAVE16 = new ImageIcon(imagePath + "Save16.gif");
  public final static Icon SAVEAS16 = new ImageIcon(imagePath + "SaveAs16.gif");
  public final static Icon PRINT16 = new ImageIcon(imagePath + "print16.gif");

  public final static Icon LINE16 = new ImageIcon(imagePath + "Line16.gif");
  public final static Icon RECTANGLE16 = new ImageIcon(imagePath + "Rectangle16.gif");
  public final static Icon CIRCLE16 = new ImageIcon(imagePath + "Circle16.gif");
  public final static Icon CURVE16 = new ImageIcon(imagePath + "Curve16.gif");

  public final static Icon RED16 = new ImageIcon(imagePath + "Red16.gif");
  public final static Icon GREEN16 = new ImageIcon(imagePath + "Green16.gif");
  public final static Icon BLUE16 = new ImageIcon(imagePath + "Blue16.gif");
  public final static Icon YELLOW16 = new ImageIcon(imagePath + "Yellow16.gif");

  // Element type definitions
  public final static int LINE      = 101;
  public final static int RECTANGLE = 102;
  public final static int CIRCLE    = 103;
  public final static int CURVE     = 104;

  // Initial conditions
  public final static int DEFAULT_ELEMENT_TYPE = LINE;
  public final static Color DEFAULT_ELEMENT_COLOR = Color.BLUE;
}