如何在 Java Swing 中使用一开始未加载的 jbutton？

Question

我正在学习 java swing，我有很多按钮，但是当我在组合框中选择某些内容时，我需要在红色区域中放置一些新按钮，问题是如果没有这些按钮，我不知道如何使用这些按钮一开始就创建。

当我在组合框中选择时，这里加载了一些按钮，我需要对它们进行一些操作：

谢谢

Answer 1

你的问题有很多可以解释的地方。

因此，例如，如果值是固定的，我会将它们分成单独的面板，隔离它们的功能和工作流程，然后根据选择的内容简单地交换它们。

import java.awt.CardLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Main {
    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());

            JComboBox<String> comboBox = new JComboBox<>();
            DefaultComboBoxModel<String> model = new DefaultComboBoxModel<>();
            model.addElement("Option A");
            model.addElement("Option B");
            comboBox.setModel(model);

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.insets = new Insets(8, 8, 8, 8);
            add(comboBox, gbc);

            CardLayout cardLayout = new CardLayout();
            JPanel buttonOptions = new JPanel(cardLayout);
            buttonOptions.add(new OptionAPane(), "optionA");
            buttonOptions.add(new OptionBPane(), "optionB");

            gbc.gridy = 1;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;
            add(buttonOptions, gbc);

            comboBox.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    switch (comboBox.getSelectedIndex()) {
                        case 0: 
                            cardLayout.show(buttonOptions, "optionA");
                            break;
                        case 1: 
                            cardLayout.show(buttonOptions, "optionB");
                            break;
                    }
                }
            });
        }

    }

    public class OptionAPane extends JPanel {

        public OptionAPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = gbc.REMAINDER;
            gbc.insets = new Insets(8, 8, 8, 8);

            JButton btnThis = new JButton("This");
            btnThis.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Do this");
                }
            });
            JButton btnThat = new JButton("That");
            btnThis.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Do that");
                }
            });

            add(new JLabel("A Options"), gbc);

            add(btnThis, gbc);
            add(btnThat, gbc);
        }

    }

    public class OptionBPane extends JPanel {

        public OptionBPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = gbc.REMAINDER;
            gbc.insets = new Insets(8, 8, 8, 8);

            JButton btnOther = new JButton("Other");
            btnOther.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Do other");
                }
            });
            JButton btnSomethingElse = new JButton("Something else");
            btnOther.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Do something else");
                }
            });

            add(new JLabel("B Options"), gbc);

            add(btnOther, gbc);
            add(btnSomethingElse, gbc);
        }

    }
}

但是我怎么知道什么时候点击了一个按钮。

这是将使用观察者模式的地方。 您可以根据每个面板的需要定义一个或多个侦听器，当单击面板上的按钮时，该侦听器将触发一个事件，您可以使用它

另一方面，如果您需要更动态的东西（即每个选项可以根据其他配置有不同的操作），您可以使用Action API

例如...

import java.awt.Component;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.DefaultComboBoxModel;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;

public class Main {

    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ActionGroup {

        private String description;
        private List<Action> actions;

        public ActionGroup(String description) {
            this.description = description;
            this.actions = new ArrayList<>(25);
        }


        public ActionGroup(String description, List<Action> actions) {
            this.description = description;
            this.actions = actions;
        }

        public String getDescription() {
            return description;
        }

        public void add(Action action) {
            actions.add(action);
        }

        public void remove(Action action) {
            actions.remove(action);
        }

        public List<Action> getActions() {
            return Collections.unmodifiableList(actions);
        }
    }

    public class SimpleAction extends AbstractAction {

        // You have a number of choices when using something like Action,
        // You can create a custom Action based on your needs and pass
        // in the information it needs to do it's job OR, you can use
        // a observer pattern to get notified when the ActionListener
        // is triggered
        public SimpleAction(String name) {
            putValue(NAME, name);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println(getValue(NAME) + " was triggered");
        }

    }

    public class ActionGroupCellRenderer extends DefaultListCellRenderer {

        @Override
        public Component getListCellRendererComponent(JList<?> list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
            if (value instanceof ActionGroup) {
                value = ((ActionGroup)value).getDescription();
            }
            return super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
        }

    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());

            ActionGroup optionA = new ActionGroup("Option A");
            optionA.add(new SimpleAction("Cat"));
            optionA.add(new SimpleAction("Doggy"));
            optionA.add(new SimpleAction("Bunny"));
            optionA.add(new SimpleAction("Rat"));
            optionA.add(new SimpleAction("Cow"));

            ActionGroup optionB = new ActionGroup("Option B");
            optionB.add(new SimpleAction("Banana"));
            optionB.add(new SimpleAction("Apple"));
            optionB.add(new SimpleAction("Pear"));
            optionB.add(new SimpleAction("Orange"));
            optionB.add(new SimpleAction("Lemon"));

            JComboBox<ActionGroup> comboBox = new JComboBox<>();
            comboBox.setRenderer(new ActionGroupCellRenderer());    
            DefaultComboBoxModel<ActionGroup> model = new DefaultComboBoxModel<>();
            model.addElement(optionA);
            model.addElement(optionB);
            comboBox.setModel(model);

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.insets = new Insets(8, 8, 8, 8);
            add(comboBox, gbc);

            gbc.gridy = 1;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;
            ActionGroupPane buttonOptions = new ActionGroupPane();
            buttonOptions.setActionGroup(optionA);
            add(buttonOptions, gbc);

            comboBox.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    Object item = comboBox.getSelectedItem();
                    if (item instanceof ActionGroup) {
                        System.out.println(item);
                        buttonOptions.setActionGroup((ActionGroup)item);
                    }
                }
            });
        }

    }

    public class ActionGroupPane extends JPanel {

        public ActionGroupPane() {
            setLayout(new GridBagLayout());
        }

        public void setActionGroup(ActionGroup actionGroup) {
            removeAll();
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = gbc.REMAINDER;
            gbc.insets = new Insets(8, 8, 8, 8);

            add(new JLabel(actionGroup.getDescription()), gbc);

            for (Action action : actionGroup.getActions()) {
                add(new JButton(action), gbc);
            }

            revalidate();
            repaint();
        }

    }
}

Action非常强大，我建议花一些时间看看如何使用动作