Java的ActionListenr总是安装不成功无法正常运行
用cmd运行，给出提示“Exception in thread "main"java.lang.NullPointerException”。
为什么安装的监听器老是不成功呢？
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class task3 extends JFrame implements ActionListener
{
private static JFrame frame;
private static JPanel panel1;//下方
private static JPanel panel2;//图片
JLabel tips;//用户正误提示处
JButton check;//
JTextField answer;//输入答案
int newNum = 10;//初始图片数量
public task3()
{
this.setTitle("Welcom to Jungle Party");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(new BorderLayout());
this.getContentPane().add(panel1,BorderLayout.SOUTH);
this.setBounds(120,120,1200,600);
panel1 = new JPanel();
panel1.setLayout(new BoxLayout(panel1,BoxLayout.Y_AXIS));
answer = new JTextField(10);
tips = new JLabel("Hello");
check = new JButton("check");
panel1.add(tips);
panel1.add(answer);
panel1.add(check);
simpleListener ourListener = new simpleListener();
check.addActionListener(ourListener);
this.setVisible(true);
}
private class simpleListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String buttonName = e.getActionCommand();
if(buttonName.equals("check"));
{
tips.setText("hahaha successful");
}
}
}
public static void main(String[] args)
{
task3 abc = new task3();
}
} |
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