我认为我的错误是我的 showGreeting() 方法。具体在试试。当用户按下“获取问候语”按钮时，我希望它显示一个对话框，上面写着“问候，名字 + MI + 姓氏”当用户将字段留空时，我创建的错误出现了，这很好，但我没有了解为什么我的正常问候语不起作用。
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class GreetingApp extends JFrame {
private static final long serialVersionUID = 1L;
private final JTextField firstNameField,middleNameField,lastNameField;
private final JButton greetingButton;
public GreetingApp() {
super("Greetings");
this.firstNameField = new JTextField(8);
this.middleNameField = new JTextField(8);
this.lastNameField = new JTextField(8);
this.greetingButton = new JButton("Get Greeting");
greetingButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(final ActionEvent ae){
showGreeting();
}
});
final Container mainPanel = getContentPane();
mainPanel.setLayout(new BorderLayout());
final JPanel inputPanel = new JPanel();
final JPanel buttonPanel = new JPanel();
inputPanel.setLayout(new GridLayout(3,3,2,2));
buttonPanel.setLayout(new BorderLayout());
JSeparator sep = new JSeparator();
inputPanel.add(new JLabel("First Name: "),JLabel.LEFT_ALIGNMENT);
inputPanel.add(firstNameField);
inputPanel.add(new JLabel("MI: "),JLabel.LEFT_ALIGNMENT);
inputPanel.add(middleNameField);
inputPanel.add(new JLabel("Last Name: "),JLabel.LEFT_ALIGNMENT);
inputPanel.add(lastNameField);
mainPanel.add(inputPanel,BorderLayout.PAGE_START);
buttonPanel.add(sep,BorderLayout.PAGE_START);
buttonPanel.add(greetingButton);
mainPanel.add(buttonPanel,BorderLayout.PAGE_END);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
private String getFullName() throws IllegalStateException{
if(firstNameField.getText().trim().length() == 0){
throw new IllegalArgumentException("First name cannot be blank");
}
if(middleNameField.getText().trim().length() == 0){
throw new IllegalArgumentException("Middle name cannot be blank");
}
if(lastNameField.getText().trim().length() == 0){
throw new IllegalArgumentException("Last name cannot be blank");
}
return "Greetings, "+this.firstNameField+" "+ this.middleNameField +". "+this.lastNameField+"!";
}
private void showGreeting(){
try{
String message = getFullName();
JOptionPane.showMessageDialog(this, message, "Greetings",JOptionPane.PLAIN_MESSAGE);
}catch(final IllegalArgumentException iae){
JOptionPane.showMessageDialog(this,
iae.getMessage(),
"Error",
JOptionPane.ERROR_MESSAGE);
}
}
public static void main(String[] args) {
GreetingApp g = new GreetingApp();
}
}
编辑：没关系，伙计们知道了，我必须添加一个 .getText() return "Greetings, "+this.firstNameField+" "+ this.middleNameField +". "+this.lastNameField+"!"; 在每个字段之后从它们实际获取文本