java Java中按钮的动态生成

Dynamic generation of buttons in Java

提问by Kevin Lacquement

I am trying to dynamically generate a form. Basically, I want to load a list of items for purchase, and generate a button for each. I can confirm that the buttons are being generated with the debugger, but they aren't being displayed. This is inside a subclass of JPanel:

我正在尝试动态生成表单。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。我可以确认按钮是用调试器生成的，但没有显示。这是在以下子类中JPanel：

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();
}

DrinkButtonis a subclass of JButton. Any ideas?

DrinkButton是 的子类JButton。有任何想法吗？

采纳答案by Tomasz Nurkiewicz

Works on my computer...

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);
            }
        });
    }
}

As far as I remember your version was working as well, although I had to remove your "drinking" code. Start from this example (it shows nice 4x4 grid of buttons) and determine what is wrong with your code.

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 按钮网格）并确定您的代码有什么问题。

回答by trashgod

You can use revalidate(), as shown in this example.

您可以使用revalidate()，如本例所示。

Addendum: Here's my variation on @mKorbel's interesting answerthat shows a similar result for GridLayout. It looks like repaint()may be necessary after revalidate().

附录：这是我对@mKorbel 有趣答案的变体，它显示了类似的结果GridLayout。看来repaint()以后可能需要revalidate()。

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();
            }
        });
    }
}

回答by mKorbel

example about validate() revalidate() plus repaint(), look like as required for correct output to the GUI, layed by some of LayourManagers

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

EDIT: as trashgodnoticed, I added Schedule a job for the EDT

编辑：正如trashgod注意到的那样，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();
            }
        });
    }
}