ITEEDU

7. 对话框

在这个例子里直接重写了早期的ToeTest.java程序。在这个新的版本里，任何事件都被安放进一个内部类中。虽然这完全消除了需要记录产生的任何类的麻烦，作为ToeTest.java的一个例子，它能使内部类的概念变得不那遥远。在这点，内嵌类被嵌套达四层之深！我们需要的这种设计决定了内部类的优点是否值得增加更加复杂的事物。另外，当我们创建一个非静态的内部类时，我们将捆绑非静态类到它周围的类上。有时，单独的类可以更容易地被复用。

//: ToeTestNew.java
// Demonstration of dialog boxes
// and creating your own components
import java.awt.*;
import java.awt.event.*;

public class ToeTestNew extends Frame {
  TextField rows = new TextField("3");
  TextField cols = new TextField("3");
  public ToeTestNew() {
    setTitle("Toe Test");
    Panel p = new Panel();
    p.setLayout(new GridLayout(2,2));
    p.add(new Label("Rows", Label.CENTER));
    p.add(rows);
    p.add(new Label("Columns", Label.CENTER));
    p.add(cols);
    add(p, BorderLayout.NORTH);
    Button b = new Button("go");
    b.addActionListener(new BL());
    add(b, BorderLayout.SOUTH);
  }
  static final int BLANK = 0;
  static final int XX = 1;
  static final int OO = 2;
  class ToeDialog extends Dialog {
    // w = number of cells wide
    // h = number of cells high
    int turn = XX; // Start with x's turn
    public ToeDialog(int w, int h) {
      super(ToeTestNew.this, 
        "The game itself", false);
      setLayout(new GridLayout(w, h));
      for(int i = 0; i < w * h; i++)
        add(new ToeButton());
      setSize(w * 50, h * 50);
      addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e){
          dispose();
        }
      });
    }
    class ToeButton extends Canvas {
      int state = BLANK;
      ToeButton() {
        addMouseListener(new ML());
      }
      public void paint(Graphics  g) {
        int x1 = 0;
        int y1 = 0;
        int x2 = getSize().width - 1;
        int y2 = getSize().height - 1;
        g.drawRect(x1, y1, x2, y2);
        x1 = x2/4;
        y1 = y2/4;
        int wide = x2/2;
        int high = y2/2;
        if(state == XX) {
          g.drawLine(x1, y1, 
            x1 + wide, y1 + high);
          g.drawLine(x1, y1 + high, 
            x1 + wide, y1);
        }
        if(state == OO) {
          g.drawOval(x1, y1, 
            x1 + wide/2, y1 + high/2);
        }
      }
      class ML extends MouseAdapter {
        public void mousePressed(MouseEvent e) {
          if(state == BLANK) {
            state = turn;
            turn = (turn == XX ? OO : XX);
          } 
          else
            state = (state == XX ? OO : XX);
          repaint();
        }
      }
    }
  }
  class BL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      Dialog d = new ToeDialog(
        Integer.parseInt(rows.getText()),
        Integer.parseInt(cols.getText()));
      d.show();
    }
  }
  public static void main(String[] args) {
    Frame f = new ToeTestNew();
    f.addWindowListener(
      new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
          System.exit(0);
        }
      });
    f.setSize(200,100);
    f.setVisible(true);
  }
} ///:~

由于“静态”的东西只能位于类的外部一级，所以内部类不可能拥有静态数据或者静态内部类。