Java 将JFrame设置为显示在中心不工作？

我正在开发一个swing应用程序，并创建了一个登录表单。我将其设置为显示在屏幕中央但不起作用：（我尝试了两种方法（1）和（2），但都不起作用。 我不明白为什么。因为这两种解决方案都在这个网站上

我的代码：

public class LoginForm extends javax.swing.JFrame {


    public LoginForm() {    

        /*Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        this.setLocation(dim.width/2-this.getSize().width/2, dim.height/2-                         this.getSize().height/2);*/  // ----> (1)

        setLocationRelativeTo(null); // ----> (2)


        initComponents();
    }


    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPasswordField jPasswordField1;
    private javax.swing.JTextField jTextField1;
    private java.awt.Label label1;

    private void initComponents() {


        setUndecorated(true);

        jPanel1 = new javax.swing.JPanel();
        jTextField1 = new RoundJTextField(20);
        jPasswordField1 = new RoundJPasswordField(20);
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        label1 = new java.awt.Label();
        jButton2 = new javax.swing.JButton();
        jButton1 = new javax.swing.JButton();
        jButton3 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(new java.awt.Color(255, 255, 255));
        setBounds(new java.awt.Rectangle(5, 0, 0, 0));
        setName("LogInFrame"); // NOI18N
        setResizable(false);

        jPanel1.setBackground(new java.awt.Color(255, 255, 255));
        jPanel1.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));

        jLabel1.setFont(new java.awt.Font("Segoe UI", 0, 18)); // NOI18N
        jLabel1.setText("Username");

        jLabel2.setFont(new java.awt.Font("Segoe UI", 0, 18)); // NOI18N
        jLabel2.setText("Password");


        label1.setFont(new java.awt.Font("SansSerif", 1, 18)); // NOI18N
        label1.setText("UAC Login");

        jButton2.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/windows_close_program.png"))); // NOI18N
        jButton2.setActionCommand("loginExit");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });

        jButton1.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/go.JPG"))); // NOI18N
        jButton1.setActionCommand("LoginButton");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jButton3.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/join.JPG"))); // NOI18N
        jButton3.setText("jButton3");

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGap(60, 60, 60)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 104, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jLabel2))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addComponent(jPasswordField1, javax.swing.GroupLayout.DEFAULT_SIZE, 198, Short.MAX_VALUE)
                            .addComponent(jTextField1)
                            .addComponent(label1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(21, 21, 21)
                        .addComponent(jButton3, javax.swing.GroupLayout.PREFERRED_SIZE, 262, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 55, Short.MAX_VALUE)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 20, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap())
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                        .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 81, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(22, 22, 22))))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(20, 20, 20)
                        .addComponent(label1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 20, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(2, 2, 2)
                        .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 207, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap(46, Short.MAX_VALUE))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(57, 57, 57)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 28, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGap(40, 40, 40)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel2)
                            .addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jButton3, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(34, 34, 34))))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addGap(0, 0, Short.MAX_VALUE)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(0, 0, 0))
        );

        pack();
    }// </editor-fold>                        



    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         

        System.exit(0);
    }                                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       this.setVisible(false);
       this.dispose();
       new RegistrationForm();
    }                                        


    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Synth".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(LoginForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(LoginForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(LoginForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(LoginForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }

        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new LoginForm().setVisible(true);
            }
        });
    }                   
}

公共类LoginForm扩展了javax.swing.JFrame{
公共登录信息（）{
/*维度dim=Toolkit.getDefaultToolkit（）.getScreenSize（）；
this.setLocation（dim.width/2-this.getSize（）.width/2，dim.height/2-this.getSize（）.height/2）；*/-->（1）
setLocationRelativeTo（空）；//--->（2）
初始化组件（）；
}
私有javax.swing.JButton jButton1；
私有javax.swing.JButton jButton2；
私有javax.swing.JButton jButton3；
私有javax.swing.JLabel jLabel1；
私有javax.swing.JLabel jLabel2；
私有javax.swing.JPanel jPanel1；
私有javax.swing.JPasswordField jPasswordField1；
私有javax.swing.JTextField jTextField1；
私有java.awt.label1；
私有组件（）{
未装饰的设置（真实）；
jPanel1=newjavax.swing.JPanel（）；
jTextField1=新一轮jtextfield（20）；
jPasswordField1=新一轮jpasswordfield（20）；
jLabel1=newjavax.swing.JLabel（）；
jLabel2=newjavax.swing.JLabel（）；
label1=newjava.awt.Label（）；
jButton2=newjavax.swing.JButton（）；
jButton1=newjavax.swing.JButton（）；
jButton3=newjavax.swing.JButton（）；
setDefaultCloseOperation（javax.swing.WindowConstants.EXIT_ON_CLOSE）；
setBackground（新java.awt.Color（255、255、255））；
setBounds（新java.awt.Rectangle（5,0,0,0））；
setName（“LogInFrame”）；//NOI18N
可设置大小（假）；
setBackground（新java.awt.Color（255、255、255））；
setBorder（javax.swing.BorderFactory.createLineBorder（新java.awt.Color（0,0,0））；
jLabel1.setFont（新的java.awt.Font（“SegoeUI”，0，18））；//NOI18N
jLabel1.setText（“用户名”）；
jLabel2.setFont（新的java.awt.Font（“SegoeUI”，0，18））；//NOI18N
jLabel2.setText（“密码”）；
label1.setFont（新的java.awt.Font（“SansSerif”，1，18））；//NOI18N
标签1.setText（“UAC登录”）；
jButton2.setIcon（新的javax.swing.ImageIcon（getClass（）.getResource（“/images/windows\u close\u program.png”）；//NOI18N
jButton2.setActionCommand（“loginExit”）；
jButton2.addActionListener（新java.awt.event.ActionListener（）{
public void actionPerformed（java.awt.event.ActionEvent evt）{
jButton2ActionPerformed（evt）；
}
});
jButton1.setIcon（新的javax.swing.ImageIcon（getClass（）.getResource（“/images/go.JPG”）；//NOI18N
jButton1.setActionCommand（“登录按钮”）；
jButton1.addActionListener（新java.awt.event.ActionListener（）{
public void actionPerformed（java.awt.event.ActionEvent evt）{
jButton1ActionPerformed（evt）；
}
});
jButton3.setIcon（新的javax.swing.ImageIcon（getClass（）.getResource（“/images/join.JPG”）；//NOI18N
setText（“jButton3”）；
javax.swing.GroupLayout jPanel1Layout=新的javax.swing.GroupLayout（jPanel1）；
setLayout（jPanel1Layout）；
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（jpanellayout.createSequentialGroup（）
.addGap（60,60,60）
.addGroup（jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（jpanellayout.createSequentialGroup（）
.addGroup（jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addComponent（jLabel1，javax.swing.GroupLayout.PREFERRED_SIZE，104，javax.swing.GroupLayout.PREFERRED_SIZE）
.addComponent（jLabel2））
.addPreferredGap（javax.swing.LayoutStyle.ComponentPlacement.RELATED）
.addGroup（jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING，false）
.addComponent（jPasswordField1，javax.swing.GroupLayout.DEFAULT\u SIZE，198，Short.MAX\u值）
.addComponent（jTextField1）
.addComponent（label1，javax.swing.GroupLayout.PREFERRED\u SIZE，javax.swing.GroupLayout.DEFAULT\u SIZE，javax.swing.GroupLayout.PREFERRED\u SIZE）））
.addGroup（jpanellayout.createSequentialGroup（）
.addGap（21,21,21）
.addComponent（jButton3，javax.swing.GroupLayout.PREFERRED_SIZE，262，javax.swing.GroupLayout.PREFERRED_SIZE）））
.addPreferredGap（javax.swing.LayoutStyle.ComponentPlacement.RELATED，55，Short.MAX_值）
.addGroup（jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（javax.swing.GroupLayout.Alignment.TRAILING，jPanel1Layout.createSequentialGroup（）
.addComponent（jButton2，javax.swing.GroupLayout.PREFERRED_SIZE，20，javax.swing.GroupLayout.PREFERRED_SIZE）
.addContainerGap（））
.addGroup（javax.swing.GroupLayout.Alignment.TRAILING，jPanel1Layout.createSequentialGroup（）
.addComponent（jButton1，javax.swing.GroupLayout.PREFERRED_SIZE，81，javax.swing.GroupLayout.PREFERRED_SIZE）
.addGap（22,22,22）））
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（jpanellayout.createSequentialGroup（）
.addGroup（jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
A.
public LoginForm() {    
    /*Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
    this.setLocation(dim.width/2-this.getSize().width/2, dim.height/2-                         this.getSize().height/2);*/  // ----> (1)
    initComponents();
    pack();
    setLocationRelativeTo(null); // ----> (2)
}