Question

我是java新手，我正在编写一个登录框架，在成功登录后（到mysql数据库（使用xampp的localhost））关闭自己并打开主框架。

我的登录屏幕有一个欢迎标签，一个用户名标签，一个密码标签，一个文本字段和一个密码字段以及一个登录按钮。我希望这些组件在窗口中居中并保持居中并且不改变它们的大小，无论jpanel变得多大（通过在屏幕上将其拖动得更大或更小）。

我的问题是，如果它发生变化，我如何让它们保持居中并使其位置适应面板尺寸？让我们说面板尺寸为100 * 100，按钮为50/50，面板变为200/200，但按钮保持在50/50，如果我将其设置为水平或垂直可调整，它只会变大，但我希望它保持相同的大小，只需将其位置调整为100/100。

我无法张贴我的画面的图像，因为它似乎需要声誉，我没有因为我刚创建了我的帐户。我希望你能想象我的意思和现在的情况。

我使用GroupLayout的LoginFrame代码如下（我离开了actionlistener，因为它不相关）：

public LoginFrame() {
     setTitle("LoginFrame");
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setBounds(100, 100, 363, 270);
     contentPane = new JPanel();
     contentPane.setBackground(Color.ORANGE);
     contentPane.setBorder(new EmptyBorder(0, 0, 0, 0));
     setContentPane(contentPane);

     JLabel lblWelcome = new JLabel("Welcome");

     JLabel lblNewLabel = new JLabel("Username: ");

     textField = new JTextField();
     textField.setColumns(10);

     JLabel lblNewLabel_1 = new JLabel("Password: ");

     passwordField = new JPasswordField();

     JButton btnLogin = new JButton("Login");

        GroupLayout gl_contentPane = new GroupLayout(contentPane);
        gl_contentPane.setHorizontalGroup(
        gl_contentPane.createParallelGroup(Alignment.LEADING)
            .addGroup(gl_contentPane.createSequentialGroup()
                .addGap(107)
                .addGroup(gl_contentPane.createParallelGroup(Alignment.TRAILING)
                    .addComponent(lblNewLabel)
                    .addComponent(lblNewLabel_1))
                .addPreferredGap(ComponentPlacement.RELATED)
                .addGroup(gl_contentPane.createParallelGroup(Alignment.LEADING)
                    .addComponent(passwordField, GroupLayout.DEFAULT_SIZE, 106, Short.MAX_VALUE)
                    .addComponent(textField, GroupLayout.DEFAULT_SIZE, 104, Short.MAX_VALUE))
                .addGap(75))
            .addGroup(gl_contentPane.createSequentialGroup()
                .addGap(145)
                .addComponent(btnLogin)
                .addContainerGap(145, Short.MAX_VALUE))
            .addGroup(gl_contentPane.createSequentialGroup()
                .addGap(149)
                .addComponent(lblWelcome)
                .addContainerGap(155, Short.MAX_VALUE))
    );
    gl_contentPane.setVerticalGroup(
        gl_contentPane.createParallelGroup(Alignment.LEADING)
            .addGroup(gl_contentPane.createSequentialGroup()
                .addGap(56)
                .addComponent(lblWelcome)
                .addGap(18)
                .addGroup(gl_contentPane.createParallelGroup(Alignment.BASELINE)
                    .addComponent(textField, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addComponent(lblNewLabel))
                .addPreferredGap(ComponentPlacement.RELATED)
                .addGroup(gl_contentPane.createParallelGroup(Alignment.BASELINE)
                    .addComponent(passwordField, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addComponent(lblNewLabel_1))
                .addPreferredGap(ComponentPlacement.UNRELATED)
                .addComponent(btnLogin)
                .addContainerGap(64, Short.MAX_VALUE))
    );
    contentPane.setLayout(gl_contentPane);
 }

我希望我能得到一些有用的答案，我试着具体，告诉我是否有什么遗漏。感谢

Answer 1

出于这个目的，我建议您使用GridBagLayout（tutorial）而不是GroupLayout，因为它更简单，更灵活。它适用于GridBagConstraints（read about it parametrs）。

下一个代码在GridBagLayout的帮助下执行您想要的操作。

public class LoginFrame extends JFrame {

private JPanel contentPane;
private JTextField textField;
private JPasswordField passwordField;

public LoginFrame() {
    setTitle("LoginFrame");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 363, 270);
    contentPane = new JPanel();
    contentPane.setBackground(Color.ORANGE);
    contentPane.setBorder(new EmptyBorder(0, 0, 0, 0));
    setContentPane(contentPane);

    JLabel lblWelcome = new JLabel("Welcome");

    JLabel lblNewLabel = new JLabel("Username: ");

    textField = new JTextField();
    textField.setColumns(10);

    JLabel lblNewLabel_1 = new JLabel("Password: ");

    passwordField = new JPasswordField();

    JButton btnLogin = new JButton("Login");

    contentPane.setLayout(new GridBagLayout());

    GridBagConstraints c = new GridBagConstraints();
    c.insets = new Insets(5, 5, 5, 5);

    c.gridx = 0;
    c.gridy = 0;
    c.gridwidth = 2;
    c.anchor = GridBagConstraints.CENTER;
    contentPane.add(lblWelcome, c);

    c.gridwidth = 1;
    c.gridy = 1;
    contentPane.add(lblNewLabel, c);

    c.gridx = 1;
    contentPane.add(textField, c);

    c.fill = GridBagConstraints.HORIZONTAL;
    c.gridy = 2;
    contentPane.add(passwordField, c);

    c.fill = GridBagConstraints.NONE;
    c.gridx = 0;
    contentPane.add(lblNewLabel_1, c);

    c.gridy = 3;
    c.gridwidth = 2;
    contentPane.add(btnLogin, c);
}

public static void main(String... s) {
    LoginFrame loginFrame = new LoginFrame();
    loginFrame.setVisible(true);
}
}

如何将一组组件集中在JPanel中，无论其大小如何

1 个答案: