在Java中實現GridBagLayout的問題

Question

我正在嘗試為要構建的程序制作的“登錄”對話框用Java實現GridBagLayout。 我要使用干凈的Google登錄名。我遇到的主要問題是，使用GridBagConstraints設置的約束不起作用。 這是我希望對話框顯示的樣子。

這是我嘗試實現的對話框的代碼。

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Login_Dialog extends JDialog{

    // SEtting up the required components for the sign in

    /**
     * 
     */
    private static final long serialVersionUID = 1L;


    protected JLabel username_Label = new JLabel("Username");
    protected JLabel password_Label = new JLabel("Username");

    protected JTextField username_Field = new JTextField(30);
    protected JTextField password_Field = new JTextField(30);

    protected JButton sign_In = new JButton("Sign in!");

    public Login_Dialog() {
        setSize(600,400);
        setTitle("Sign in");

        setLayout(new GridBagLayout());

        GridBagConstraints c = new GridBagConstraints();

        c.fill = GridBagConstraints.HORIZONTAL;
        c.gridx = 0;
        c.gridy = 0;

        add(username_Label);

        c.fill = GridBagConstraints.HORIZONTAL;
//      c.weightx = 0.5;
        c.gridx = 1;
        c.gridy = 0;

        add(username_Field);

        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 2;

        add(password_Label);

        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 4;

        add(password_Field);

        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 5;

        add(sign_In);

        setVisible(true);

    }

}

更新：

我進行了一些更改，似乎可以達到我想要的結果。 現在的問題是，所有內容都居中並且按鈕的長度太寬。 另外，我希望文本字段和標簽更大。

這是GridBagLayout的更新

//cusotmization of buttons
        Dimension signD = sign_In.getPreferredSize();
        signD.height = 50;
        signD.width = 30;

        sign_In.setPreferredSize(signD);


        GridBagConstraints c = new GridBagConstraints();

        c.fill = GridBagConstraints.HORIZONTAL;
        c.gridx = 0;
        c.gridy = 0;

        add(username_Label,c);

        c.fill = GridBagConstraints.HORIZONTAL;
//      c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 1;

        add(username_Field,c);

        c.fill = GridBagConstraints.HORIZONTAL;
//      c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 2;

        add(password_Label,c);

        c.fill = GridBagConstraints.HORIZONTAL;
//      c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 3;

        add(password_Field,c);
//      
//      c.fill = GridBagConstraints.HORIZONTAL;
//      c.weightx = 0.5;
        c.gridx = 0;
        c.gridy = 5;
//      
        add(sign_In,c);

Answer 1

您必須在add()添加約束對象

范例：

add(username_Field, c);

其中c是您的GridBagConstraints。

這是一個完整的例子：

package gui;

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.WindowConstants;

@SuppressWarnings("serial")
public class LoginPanel extends JPanel
{
    private static final Dimension TFIELD_SZ = new Dimension(120, 20);

    public LoginPanel()
    {
        super(new GridBagLayout());

        final GridBagConstraints cst = new GridBagConstraints();
        cst.insets = new Insets(0, 5, 0, 5);
        cst.weightx = 0.5;
        cst.weighty = 0.5;
        cst.anchor = GridBagConstraints.LINE_START;

        // Username
        cst.gridx = 0;
        cst.gridy = 0;
        this.add(new JLabel("Username:"), cst);
        cst.gridy = 1;
        cst.gridwidth = 2;
        final JTextField uTField = new JTextField();
        uTField.setMinimumSize(TFIELD_SZ);
        uTField.setPreferredSize(TFIELD_SZ);
        this.add(uTField, cst);

        // Password
        cst.gridwidth = 1;
        cst.gridy = 2;
        this.add(new JLabel("Password:"), cst);
        cst.gridy = 3;
        cst.gridwidth = 2;
        final JTextField pwTField = new JTextField();
        pwTField.setMinimumSize(TFIELD_SZ);
        pwTField.setPreferredSize(TFIELD_SZ);
        this.add(pwTField, cst);

        // Buttons
        cst.anchor = GridBagConstraints.CENTER;
        cst.gridy = 4;
        cst.gridwidth = 1;
        this.add(new JButton("Sign in"), cst);
        cst.gridx = 1;
        this.add(new JButton("Sign up"), cst);

    }

    public static void main(final String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                final JDialog myDialog = new JDialog();
                myDialog.setTitle("Sign in");
                myDialog.setSize(180, 170);
                myDialog.setContentPane(new LoginPanel());
                myDialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
                myDialog.setVisible(true);
            }
        });
    }
}