java - 如何从组合框中的数字列表向 JPanel 添加按钮

Question

我正在尝试从组合框在 JPanel 中添加一些按钮。组合框有一个 8 个整数的数组，当选择其中一个时，我希望能够按下“执行”按钮，然后将从组合框中选择的按钮数量显示到 JPanel 中。

JPanel 最初是空的，并且“执行”按钮被禁用，直到选择某些内容为止。

我已经创建了 JPanel、comboBox 和 go 按钮，但我现在不知道如何获取和创建按钮。

充满字符串的组合框 -

String[] floorStrings = {"Select one", "1", "2", "3", "4", "5", "6", "7", "8"};
//Create the combo box
JComboBox floorList = new JComboBox(floorStrings);

actionPerformed 代码 -

        public void actionPerformed(ActionEvent e) {

        floorList.getSelectedIndex();
        //int i = Integer.valueOf((String) floorList);

    if (e.getSource() == go) {
        go.setText("Stop");
        System.out.print("Clicked " + floorList);
        p3.add(go, BorderLayout.NORTH);
    } 

}

Answer 1

将 ActionListener 附加到“Go”按钮。在 actionPerformed 方法中，您需要从 JComboBox 获取值，只需使用 getSelectedValue 即可。这将返回一个对象。检查该对象是否不为 null 并尝试将其转换为 int(即 (int)value)。

如果转换成功，只需创建一个 for-next 循环，根据组合框中的值循环 n 次并创建按钮，将它们添加到您的面板中。

看看How to Write an Action Listener和 How to use Combo Boxes和 The for Statement了解更多详情

用示例更新

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.management.StringValueExp;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestComboBox08 {

    public static void main(String[] args) {
        new TestComboBox08();
    }

    public TestComboBox08() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JComboBox floorList;
        private JPanel buttons;

        public TestPane() {
            setLayout(new BorderLayout());
            String[] floorStrings = {"Select one", "1", "2", "3", "4", "5", "6", "7", "8"};
            floorList = new JComboBox(floorStrings);
            JButton go = new JButton("Go");
            go.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    int count = floorList.getSelectedIndex();
                    buttons.removeAll();
                    for (int index = 0; index < count; index++) {
                        buttons.add(new JButton(String.valueOf(index)));
                    }
                    buttons.revalidate();
                }
            });
            JPanel top = new JPanel(new FlowLayout(FlowLayout.CENTER));
            top.add(floorList);
            top.add(go);

            buttons = new JPanel(new GridLayout(0, 4));
            buttons.setPreferredSize(new Dimension(200, 200));

            add(top, BorderLayout.NORTH);
            add(buttons);
        }
    }
}