Question

为何出现Exception in thread "main"java.lang.IllegalArgumentException

package com.dhy.zc;
import java.awt.GridLayout;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class Login{
public Login(){
JFrame frame=new JFrame("注册");
JLabel labelImage=new JLabel(new ImageIcon("src/welcome.gif"));//放置图片
frame.add(labelImage);
frame.setSize(300,400);
frame.setVisible(true);
frame.setLayout(new GridLayout(3,1));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JLabel labelName=new JLabel("姓名");
JLabel labelAge=new JLabel("年龄");
JTextField textName = new JTextField(8);
JTextField textAge = new JTextField(8);
JLabel labelIntro = new JLabel("自我介绍");
JTextArea textAreaIntro = new JTextArea("自我介绍",3,8);
JScrollPane scrollPane=new JScrollPane(textAreaIntro ,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
frame.add(labelImage);
frame.add(labelName);
frame.add(labelAge);
frame.add(textAge);
frame.add(textName);
frame.add(labelIntro);
frame.add(scrollPane);

}

}

package com.dhy.zc;

import java.awt.GridLayout;

import javax.swing.JFrame;

public class Test {
public static void main(String[] args) {

Login frame=new Login();

}
}

Answer 1

JScrollPane scrollPane=new JScrollPane(textAreaIntro, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
这行代码的最后两个参数位置对调一下。
另外，frame.add(scrollPane);后面加一行：frame.setVisible(true);否则显示不出来。