添加到面板时组件未出现

Question

因此，我尝试创建一系列显示如下的单选按钮和复选框：

          Radio Button
Check Box
          Radio Button
Check Box
          Radio Button

但是，我仍在学习Java，并且想知道是否有人可以解决此问题。 目前，按钮和框显示在正确的位置，但是由于某种原因，第一个单选按钮（“ Courier”）没有显示。 如果您可以描述原因和可能的解决方案，那就太好了。

谢谢

更新的代码：

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

import javax.swing.BorderFactory;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;

public class Question2 {
    public static void main(String[] args) {
        MyFrame f = new MyFrame("Font Chooser");
        f.init();
    }
}

class MyFrame extends JFrame {
    MyFrame(String title) {
        super(title);
    }

    private JPanel mainPanel;
    private GridBagConstraints gbc = new GridBagConstraints();
    private GridBagLayout gbLayout = new GridBagLayout();

    void init() {
        mainPanel = new JPanel();
        mainPanel.setLayout(gbLayout);
        mainPanel.setBorder(BorderFactory.createEmptyBorder(10, 20, 10, 20));
        this.setContentPane(mainPanel);

        gbc.gridx = 0;
        gbc.gridy = 1;

        JCheckBox cb = new JCheckBox("Bold");
        gbLayout.setConstraints(cb, gbc);
        mainPanel.add(cb);
        gbc.gridy = 3;
        gbLayout.setConstraints(cb, gbc);
        cb = new JCheckBox("Italic");
        mainPanel.add(cb);

        gbc.gridx = 1;
        gbc.gridy = 0;

        JRadioButton rb = new JRadioButton("Times");
        gbLayout.setConstraints(rb, gbc);
        mainPanel.add(rb, gbc);
        gbc.gridy = 2;
        rb = new JRadioButton("Helvatica");
        mainPanel.add(rb, gbc);
        rb = new JRadioButton("Courier");
        gbc.gridy = 4; 
        mainPanel.add(rb, gbc);


        this.pack();
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }
}

Answer 1

3期

• Y坐标未重新分配给其他值，导致最后两个单选按钮存在于同一位置
• GridBagConstraints未用于左侧组件
• setConstraints错误地用于设置约束

结果代码：

public class GoodGridBagApp {
    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame("Font Chooser");
                frame.add(getMainPanel());
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setVisible(true);
            }

            private JPanel getMainPanel() {

                JPanel mainPanel = new JPanel();
                GridBagConstraints gbc = new GridBagConstraints();
                mainPanel.setLayout(new GridBagLayout());
                mainPanel.setBorder(BorderFactory.createEmptyBorder(10, 20, 10, 20));

                gbc.gridx = 1;
                gbc.gridy = 2;

                JCheckBox cb = new JCheckBox("Bold");
                mainPanel.add(cb, gbc);
                gbc.gridy = 4;
                cb = new JCheckBox("Italic");
                mainPanel.add(cb, gbc);

                gbc.gridx = 2;
                gbc.gridy = 1;

                JRadioButton rb = new JRadioButton("Times");
                mainPanel.add(rb, gbc);
                gbc.gridy = 3;
                rb = new JRadioButton("Helvatica");
                mainPanel.add(rb, gbc);
                rb = new JRadioButton("Courier");
                gbc.gridy = 5;
                mainPanel.add(rb, gbc);

                return mainPanel;
            }
        });
    }
}

阅读： 如何使用GridBagLayout