GUI_4_2010_03_19_补

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内部类
在一个类里访问另一个类的成员变量
好处：
可以方便的访问包装类的成员
可以更清楚的组织逻辑，防止不应该被其它类访问的类进行访问
何时使用：
该类不允许或不需要其它类进行访问时

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import java.awt.*;
import java.awt.event.*;

public class TFMath{
public static void main(String [] args){
new TFFrame().launchFrame();
}
}

class TFFrame extends Frame{
TextField num1,num2,num3;
public void launchFrame(){
    num1 = new TextField(10);
    num2 = new TextField(10);
    num3 = new TextField(20);
    Label lblPlus = new Label("+");
    Button btnEqual = new Button("=");
    //btnEqual.addActionListener(new MyMonitor(num1,num2,num3));//方法一
    //btnEqual.addActionListener(new MyMonitor(this));//方法二
    btnEqual.addActionListener(new MyMonitor());//方法三
    setLayout(new FlowLayout());
    add(num1);
    add(lblPlus);
    add(num2);
    add(btnEqual);
    add(num3);
    pack();
    setVisible(true);
}
class MyMonitor implements ActionListener{
    public void actionPerformed(ActionEvent e){
      int n1 = Integer.parseInt(num1.getText());
      int n2 = Integer.parseInt(num2.getText());
      num3.setText(""+(n1+n2));
    }
}
}

/*class MyMonitor implements ActionListener{
TextField num1,num2,num3;
public MyMonitor(TextField num1,TextField num2,TextField num3){
    this.num1 = num1;
    this.num2 = num2;
    this.num3 = num3;
}//方法一

TFFrame tf = null;
public MyMonitor(TFFrame tf){
    this.tf = tf;
}//方法二

   public void actionPerformed(ActionEvent e){
   int n1 = Integer.parseInt(tf.num1.getText());
   int n2 = Integer.parseInt(tf.num2.getText());
   tf.num3.setText(""+(n1+n2));
     System.out.println("ok");
   }
}*/