我想做的是这个， 当我输入细节时，它将验证按下按钮时textFiled是否为空，如果它是空的，它将显示一条消息说明。 然后它将移动到下一个textFile，类似于许多基于Web的注册表单， 我想要找出的是为什么消息不会改变？
将此代码粘贴到ecilpse文件中并运行它应该显示简单的框架以及我想要做的事情。
当firstname字段为空时，消息显示在框架的底部， 谁可以解释为什么当firstname字段包含文本而middlename不包含文本时它不会显示下一条消息？
大部分逻辑都在代码的底部。
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Toolkit;
import javax.swing.JFrame;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.Color;
import javax.swing.UIManager;
import javax.swing.JPanel;
import com.jgoodies.forms.layout.FormLayout;
import com.jgoodies.forms.layout.ColumnSpec;
import com.jgoodies.forms.layout.RowSpec;
import com.jgoodies.forms.factories.FormFactory;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.Font;
import javax.swing.SwingConstants;
import javax.swing.JRadioButton;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import javax.swing.JButton;
import javax.swing.JComboBox;
public class start {
private JFrame frame;
private JTextField tfFirstname;
private JTextField tfMiddlenames;
private JTextField tfSurname;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
start window = new start();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public start() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 505, 429);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
final JPanel panelClientNew = new JPanel();
panelClientNew.setBackground(new Color(0, 102, 255));
panelClientNew.setBounds(10, 11, 469, 299);
frame.getContentPane().add(panelClientNew);
panelClientNew.setLayout(null);
JLabel lblFirstname = new JLabel("Firstname :");
lblFirstname.setHorizontalAlignment(SwingConstants.RIGHT);
lblFirstname.setVerticalAlignment(SwingConstants.BOTTOM);
lblFirstname.setForeground(new Color(255, 255, 255));
lblFirstname.setFont(new Font("Tahoma", Font.BOLD, 13));
lblFirstname.setBounds(10, 16, 163, 14);
panelClientNew.add(lblFirstname);
tfFirstname = new JTextField();
tfFirstname.setFont(new Font("Tahoma", Font.PLAIN, 13));
tfFirstname.setBounds(177, 10, 282, 27);
panelClientNew.add(tfFirstname);
tfFirstname.setColumns(10);
JLabel lblMiddlenames = new JLabel("Middlenames :");
lblMiddlenames.setHorizontalAlignment(SwingConstants.RIGHT);
lblMiddlenames.setForeground(new Color(255, 255, 255));
lblMiddlenames.setFont(new Font("Tahoma", Font.BOLD, 13));
lblMiddlenames.setBounds(10, 47, 163, 14);
panelClientNew.add(lblMiddlenames);
tfMiddlenames = new JTextField();
tfMiddlenames.setFont(new Font("Tahoma", Font.PLAIN, 13));
tfMiddlenames.setBounds(177, 41, 282, 27);
panelClientNew.add(tfMiddlenames);
tfMiddlenames.setColumns(10);
JLabel lblSurname = new JLabel("Surname :");
lblSurname.setHorizontalAlignment(SwingConstants.RIGHT);
lblSurname.setForeground(new Color(255, 255, 255));
lblSurname.setFont(new Font("Tahoma", Font.BOLD, 13));
lblSurname.setBounds(10, 78, 163, 14);
panelClientNew.add(lblSurname);
tfSurname = new JTextField();
tfSurname.setFont(new Font("Tahoma", Font.PLAIN, 13));
tfSurname.setBounds(177, 72, 282, 27);
panelClientNew.add(tfSurname);
tfSurname.setColumns(10);
JButton btnAdd = new JButton("Add");
btnAdd.addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent arg0) {
/*
*
*
*
*I am trying to create a message that validates on certain circumstances
*
*
*
*/
if(tfFirstname.getText().equals(null) || tfFirstname.getText().equals("") || tfFirstname.getText().equals(false)) {
JPanel panelMessage = new JPanel();
panelMessage.setBackground(new Color(30, 144, 255));
panelMessage.setBounds(10, 321, 469, 29);
frame.getContentPane().add(panelMessage);
JLabel lblPersonSaved = new JLabel("Please Enter Firstname :");
lblPersonSaved.setForeground(new Color(255, 255, 255));
lblPersonSaved.setFont(new Font("Tahoma", Font.BOLD, 15));
panelMessage.add(lblPersonSaved);
frame.revalidate();
panelMessage.revalidate();
frame.repaint();
}
else if (tfMiddlenames.getText().equals(null) || tfMiddlenames.getText().equals("") || tfMiddlenames.getText().equals(false)) {
JPanel panelMessage = new JPanel();
panelMessage.setBackground(new Color(30, 144, 255));
panelMessage.setBounds(10, 321, 469, 29);
frame.getContentPane().add(panelMessage);
JLabel lblPersonSaved = new JLabel("Please Enter Middlenames :");
lblPersonSaved.setForeground(new Color(255, 255, 255));
lblPersonSaved.setFont(new Font("Tahoma", Font.BOLD, 15));
panelMessage.add(lblPersonSaved);
frame.revalidate();
panelMessage.revalidate();
frame.repaint();
}
else if (tfSurname.getText().equals(null) || tfSurname.getText().equals("") || tfSurname.getText().equals(false)) {
JPanel panelMessage = new JPanel();
panelMessage.setBackground(new Color(30, 144, 255));
panelMessage.setBounds(10, 321, 469, 29);
frame.getContentPane().add(panelMessage);
JLabel lblPersonSaved = new JLabel("Please Enter Surname :");
lblPersonSaved.setForeground(new Color(255, 255, 255));
lblPersonSaved.setFont(new Font("Tahoma", Font.BOLD, 15));
panelMessage.add(lblPersonSaved);
frame.revalidate();
panelMessage.revalidate();
frame.repaint();
}
else {
//Validation has passed
}
}
});
btnAdd.setBounds(370, 265, 89, 23);
panelClientNew.add(btnAdd);
}
}
答案 0 :(得分：4)
我建议您使用InputVerifier，因为这样可以在允许您甚至离开JTextField之前验证JTextField的内容是否正确（以任何方式定义此内容）。现在它不会阻止你按下其他JButton等等，所以如果你有一个提交按钮，你需要采取其他预防措施。检查JTextField是否为空的简单InputVerifier示例如下所示：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
@SuppressWarnings("serial")
public class InputVerifierExample extends JPanel {
public static final Color WARNING_COLOR = Color.red;
private JTextField firstNameField = new JTextField(10);
private JTextField middleNameField = new JTextField(10);
private JTextField lastNameField = new JTextField(10);
private JTextField[] nameFields = {
firstNameField,
middleNameField,
lastNameField };
private JLabel warningLabel = new JLabel(" ");
public InputVerifierExample() {
warningLabel.setOpaque(true);
JPanel namePanel = new JPanel();
namePanel.add(new JLabel("Name:"));
MyInputVerifier verifier = new MyInputVerifier();
for (JTextField field : nameFields) {
field.setInputVerifier(verifier);
namePanel.add(field);
}
namePanel.add(new JButton(new SubmitBtnAction()));
setLayout(new BorderLayout());
add(namePanel, BorderLayout.CENTER);
add(warningLabel, BorderLayout.SOUTH);
}
private class SubmitBtnAction extends AbstractAction {
public SubmitBtnAction() {
super("Submit");
}
@Override
public void actionPerformed(ActionEvent e) {
// first check all fields aren't empty
for (JTextField field : nameFields) {
if (field.getText().trim().isEmpty()) {
return; // return if empty
}
}
String name = "";
for (JTextField field : nameFields) {
name += field.getText() + " ";
field.setText("");
}
name = name.trim();
JOptionPane.showMessageDialog(InputVerifierExample.this, name, "Name Entered",
JOptionPane.INFORMATION_MESSAGE);
}
}
private class MyInputVerifier extends InputVerifier {
@Override
public boolean verify(JComponent input) {
JTextField field = (JTextField) input;
if (field.getText().trim().isEmpty()) {
warningLabel.setText("Please do not leave this field empty");
warningLabel.setBackground(WARNING_COLOR);
return false;
}
warningLabel.setText("");
warningLabel.setBackground(null);
return true;
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("InputVerifier Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new InputVerifierExample());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
答案 1 :(得分：3)
在start_up上只启用第一个JTextField，如果在第一个JTextField中输入任何（由你决定）字符，然后启用第二个JTextField，依此类推......，
如果您想过滤，更改或替换来自键盘的输出，请使用DocumentFilter
change background for example to Color.red（来自DocumentListeners events），如果JTextFields中的一个包含incorect lenght，数据，例如
同意HFOE关于LayoutManagers