救我！关于事件处理，内部类的问题！

Question

你的background变量定义在了JPanel里面，应该在D和E中各自定义一个：
...
private class D implements ActionListener
{
    private Color background;
    ...
}
private class E implements ActionListener
{
    private Color background;
    ...
}

Answer 1

我想这与内部类的数量并没有必然关系。只不过被你写成这种样子，setBackground和repaint让编译器误以为是内部类的，所以没有成功。你在他们之前加上需要的frame或者panel应该就可以了。

Answer 2

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class A
{
        public static void main(String[] args)
        {
                B b=new B();
                b.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                b.show();
        }
}
class B extends JFrame
{
        public B()
        {
                setTitle("我靠");
                setSize(W,H);                C c=new C();
                Container content=getContentPane();
                content.add(c);
        }
        public static final int W=300;
        public static final int H=200;
}
class C extends JPanel
{
        public C()
        {
                JButton button1=new JButton("bule");
                JButton button2=new JButton("white");                add(button1);
                add(button2);                D action1=new D(Color.BLUE);
                button1.addActionListener(action1);                E action2=new E(Color.white);
                button2.addActionListener(action2);
        }
        private class D implements ActionListener
        {
                public D(Color d)
                {
                        backgroundd=d;
                }
                public void actionPerformed(ActionEvent event)
                {
                        setBackground(backgroundd);
                        repaint();
                }
        }        private class E implements ActionListener
        {
                public E(Color e)
                {
                        backgrounde=e;
                }
                public void actionPerformed(ActionEvent event)
                {
                        setBackground(backgrounde);//分别设成自己的color
                        repaint();
                }
        }
        private Color backgrounde;
        private Color backgroundd;//add
}

Answer 3

刚才没仔细看程序就抢着发了，看过之后的确是因为你的background没有声明为各自类的全局变量所致。

Answer 4

D action1=new D(Color.bule);
button1.addActionListener(action1);

E action2=new E(Color.white);
button2.addActionListener(action2);
这两句出错，E和D类的构造函数需要2个Color对象做参数！！