关于java：匿名内部类 – 非法启动表达式

anonymous inner class - illegal start of expression

我正在编写一个进度条的代码，需要声明一个匿名的内部类，但是当我这样做时，我会得到这些：

Lab2Part2.java:25：错误：非法启动表达式
public void actionPerformed(ActionEvent e)
^
Lab2Part2.java:25：错误：非法启动表达式
public void actionPerformed(ActionEvent e)
^
Lab2Part2.java:25：错误：';' 预期
public void actionPerformed(ActionEvent e)
^
Lab2Part2.java:25：错误：';' 预期
public void actionPerformed(ActionEvent e)

这是代码：

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

public class Lab2Part2 extends JFrame implements ActionListener
{

private JFrame frame;
private JButton button;
private JPanel panel;

public Lab2Part2()
{
setLayout(new GridLayout());
frame = new JFrame();
button = new JButton("Let's start this show");
panel = new JPanel();
panel.add(button);

InnerProgress prog1 = new InnerProgress("Progress 1:");
InnerProgress prog2 = new InnerProgress("Progress 2:");

button.addActionListener(new ActionListener());

//this is where it throws errors
public void actionPerformed(ActionEvent e)
{
Object source = e.getSource();
if(source == button)
{
Thread th1 = new Thread(prog1);
Thread th2 = new Thread(prog2);
th1.start();
th2.start();
}
}

add(panel);
add(prog1);
add(prog2);

setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);
pack();
}

public static void main(String [] args)
{
new Lab2Part2();
}

class InnerProgress extends JPanel implements Runnable
{
private String progress;
private JProgressBar bar;

public InnerProgress(String _progress)
{
progress = _progress;
add(bar);
}

public void run()
{
System.out.println("We are running:" + progress);
}
}
}

准确地看这些方面：

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button.addActionListener(new ActionListener());

//this is where it throws errors
public void actionPerformed(ActionEvent e) {
Object source = e.getSource();
if (source == button) {
Thread th1 = new Thread(prog1);
Thread th2 = new Thread(prog2);
th1.start();
th2.start();
}
}

你在这里做的是禁止接口的实例化，然后在另一种方法的主体中创建方法，这也是禁止的。

当然，这不是你想要做的。

当然，你想在这个ActionListener中实现actionPerformer，这样就完成了：

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button.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {
Object source = e.getSource();
if(source == button) {
Thread th1 = new Thread(prog1);
Thread th2 = new Thread(prog2);
th1.start();
th2.start();
}

});