Java中按钮的动态生成

Question

我正在尝试动态生成一个表单。基本上，我想加载要购买的项目列表，并为每个项目生成一个按钮。我可以确认这些按钮是使用调试器生成的，但它们没有显示出来。这是在JPanel 的子类中：

private void generate() {
    JButton b = new JButton("height test");
    int btnHeight = b.getPreferredSize().height;
    int pnlHeight = this.getPreferredSize().height;
    int numButtons = pnlHeight / btnHeight;

    setLayout(new GridLayout(numButtons, 1));

    Iterator<Drink> it = DrinkMenu.iterator();

    for (int i = 0; i <= numButtons; ++i) {
        if (!it.hasNext()) {
            break;
        }
        final Drink dr = it.next();
        b = new DrinkButton(dr);
        b.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                order.addDrink(dr);
        }});
        add(b);
    }
    revalidate();
}

DrinkButton 是JButton 的子类。有什么想法吗？

Answer 1

在我的电脑上工作...

public class Panel extends JPanel {

    public Panel() {
        setLayout(new java.awt.GridLayout(4, 4));
        for (int i = 0; i < 16; ++i) {
            JButton b = new JButton(String.valueOf(i));
            b.addActionListener(new java.awt.event.ActionListener() {
                public void actionPerformed(java.awt.event.ActionEvent e) {
                    //...
                }
            });
            add(b);
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable(){
            @Override
            public void run(){
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setSize(new Dimension(300, 300));
                frame.add(new Panel());
                frame.setVisible(true);
            }
        });
    }
}

据我所知，您的版本也可以正常工作，尽管我不得不删除您的“饮酒”代码。从这个例子开始（它显示了漂亮的 4x4 网格按钮）并确定您的代码有什么问题。

Answer 2

您可以使用revalidate()，如example所示。

附录：这是我对@mKorbel 有趣的answer 的变体，它显示了GridLayout 的类似结果。看起来repaint() 在revalidate() 之后可能是必要的。

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

/** @see https://stackoverflow.com/questions/6395105 */
public class ValidateRevalidateRepaint {

    private JPanel center;
    private boolean validate = false;
    private boolean revalidate = true;
    private boolean repaint = true;

    public ValidateRevalidateRepaint() {
        center = new JPanel(new GridLayout(1, 0, 10, 10));
        JFrame f = new JFrame();
        f.setTitle("VRR");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(center, BorderLayout.CENTER);
        f.add(getRadioPanel(), BorderLayout.EAST);
        f.add(getCheckBoxPanel(), BorderLayout.SOUTH);
        makeChange(4);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private JPanel getRadioPanel() {
        JPanel panel = new JPanel(new GridLayout(0, 1));
        ButtonGroup group = new ButtonGroup();
        ActionListener l = new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JRadioButton radio = (JRadioButton) e.getSource();
                int n = Integer.parseInt(radio.getActionCommand());
                makeChange(n);
            }
        };
        for (int j = 0; j < 4; j++) {
            String s = String.valueOf(j + 1);
            JRadioButton radio = new JRadioButton(s);
            radio.setActionCommand(s);
            radio.addActionListener(l);
            group.add(radio);
            panel.add(radio);
            if (j == 3) {
                group.setSelected(radio.getModel(), true);
            }
        }
        return panel;
    }

    private JPanel getCheckBoxPanel() {
        final String[] operations = {"validate", "revalidate", "repaint"};
        ActionListener l = new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JCheckBox checkBox = (JCheckBox) e.getSource();
                String ac = checkBox.getActionCommand();
                boolean state = checkBox.isSelected();
                if (ac.equals("validate")) {
                    validate = state;
                }
                if (ac.equals("revalidate")) {
                    revalidate = state;
                }
                if (ac.equals("repaint")) {
                    repaint = state;
                }
            }
        };
        JPanel panel = new JPanel();
        for (int j = 0; j < operations.length; j++) {
            JCheckBox check = new JCheckBox(operations[j]);
            if (j == 0) {
                check.setSelected(false);
            } else {
                check.setSelected(true);
            }
            check.setActionCommand(operations[j]);
            check.addActionListener(l);
            panel.add(check);
        }
        return panel;
    }

    private void makeChange(int number) {
        center.removeAll();
        for (int j = 0; j < number; j++) {
            center.add(getFiller());
        }
        if (validate) {
            center.validate();
        }
        if (revalidate) {
            center.revalidate();
        }
        if (repaint) {
            center.repaint();
        }
    }

    private JPanel getFiller() {
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createLineBorder(Color.blue, 5));
        panel.setBackground(Color.red);
        panel.setPreferredSize(new Dimension(50, 50));
        return panel;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new ValidateRevalidateRepaint();
            }
        });
    }
}

Answer 3

关于 validate() revalidate() 和 repaint() 的示例，看起来像正确输出到 GUI 所必需的，由一些 LayourManagers 铺设

编辑：trashgod 注意到，我添加了为 EDT 安排工作

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

    public class ValidateRevalidateRepaint {

        private JPanel panel;
        private GridBagConstraints gbc;
        private boolean validate, revalidate, repaint;

        public ValidateRevalidateRepaint() {
            validate = revalidate = repaint = false;
            panel = new JPanel(new GridBagLayout());
            gbc = new GridBagConstraints();
            gbc.insets = new Insets(0, 20, 0, 20);
            panel.add(getFiller(), gbc);
            JFrame f = new JFrame();
            f.setJMenuBar(getMenuBar());
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.getContentPane().add(panel);
            f.getContentPane().add(getRadioPanel(), "East");
            f.getContentPane().add(getCheckBoxPanel(), "South");
            f.setSize(400, 200);
            f.setLocation(200, 200);
            f.setVisible(true);
        }

        private JMenuBar getMenuBar() {
            JMenu menu = new JMenu("change");
            ActionListener l = new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    JMenuItem item = (JMenuItem) e.getSource();
                    int n = Integer.parseInt(item.getActionCommand());
                    makeChange(n);
                }
            };
            for (int j = 1; j < 5; j++) {
                String s = String.valueOf(j) + " component";
                if (j > 1) {
                    s += "s";
                }
                JMenuItem item = new JMenuItem(s);
                item.setActionCommand(String.valueOf(j));
                item.addActionListener(l);
                menu.add(item);
            }
            JMenuBar menuBar = new JMenuBar();
            menuBar.add(menu);
            return menuBar;
        }

        private JPanel getRadioPanel() {
            JPanel panel1 = new JPanel(new GridBagLayout());
            GridBagConstraints gbc1 = new GridBagConstraints();
            gbc1.insets = new Insets(2, 2, 2, 2);
            gbc1.weighty = 1.0;
            gbc1.gridwidth = GridBagConstraints.REMAINDER;
            ButtonGroup group = new ButtonGroup();
            ActionListener l = new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    JRadioButton radio = (JRadioButton) e.getSource();
                    int n = Integer.parseInt(radio.getActionCommand());
                    makeChange(n);
                }
            };
            for (int j = 0; j < 4; j++) {
                String s = String.valueOf(j + 1);
                JRadioButton radio = new JRadioButton(s);
                radio.setActionCommand(s);
                radio.addActionListener(l);
                group.add(radio);
                panel1.add(radio, gbc1);
            }
            return panel1;
        }

        private JPanel getCheckBoxPanel() {
            final String[] operations = {"validate", "revalidate", "repaint"};
            ActionListener l = new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    JCheckBox checkBox = (JCheckBox) e.getSource();
                    String ac = checkBox.getActionCommand();
                    boolean state = checkBox.isSelected();
                    if (ac.equals("validate")) {
                        validate = state;
                    }
                    if (ac.equals("revalidate")) {
                        revalidate = state;
                    }
                    if (ac.equals("repaint")) {
                        repaint = state;
                    }
                }
            };
            JPanel panel2 = new JPanel();
            for (int j = 0; j < operations.length; j++) {
                JCheckBox check = new JCheckBox(operations[j]);
                check.setActionCommand(operations[j]);
                check.addActionListener(l);
                panel2.add(check);
            }
            return panel2;
        }

        private void makeChange(int number) {
            panel.removeAll();
            for (int j = 0; j < number; j++) {
                panel.add(getFiller(), gbc);
            }
            if (validate) {
                panel.validate();
            }
            if (revalidate) {
                panel.revalidate();
            }
            if (repaint) {
                panel.repaint();
            }
        }

        private JPanel getFiller() {
            JPanel panel3 = new JPanel();
            panel3.setBackground(Color.red);
            panel3.setPreferredSize(new Dimension(40, 40));
            return panel3;
        }

        public static void main(String[] args) {//added Schedule a job for the EDT
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ValidateRevalidateRepaint rVR = new ValidateRevalidateRepaint();
            }
        });
    }
}