在 NetBeans 上动态启用/禁用多个 JComboBox

Question

如何通过用户输入动态设置启用/禁用这么多JCombobox？

我有多个 JComboBox 这样的简单设计：

class foo{
    private javax.swing.JButton jButton1;
    private javax.swing.JComboBox<String> jComboBox1;
    private javax.swing.JComboBox<String> jComboBox2;
    private javax.swing.JComboBox<String> jComboBox3;
    private javax.swing.JComboBox<String> jComboBox4;
    private javax.swing.JComboBox<String> jComboBox5;
    private javax.swing.JComboBox<String> jComboBox6;
    private javax.swing.JComboBox<String> jComboBox7;
    private javax.swing.JComboBox<String> jComboBox8;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JTextField jTextField1;

    foo(){
        jPanel1 = new javax.swing.JPanel();
        jComboBox1 = new javax.swing.JComboBox<>();
        jComboBox2 = new javax.swing.JComboBox<>();
        jComboBox4 = new javax.swing.JComboBox<>();
        jComboBox3 = new javax.swing.JComboBox<>();
        jComboBox5 = new javax.swing.JComboBox<>();
        jComboBox6 = new javax.swing.JComboBox<>();
        jComboBox7 = new javax.swing.JComboBox<>();
        jComboBox8 = new javax.swing.JComboBox<>();
        jPanel2 = new javax.swing.JPanel();
        jTextField1 = new javax.swing.JTextField();
        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation( javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jPanel1.setLayout(new java.awt.GridLayout(8, 0));

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
        jPanel1.add(jComboBox1);

        jComboBox2.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 5", "Item 6", "Item 7", "Item 8" }));
        jPanel1.add(jComboBox2);

        jComboBox4.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 9", "Item 10", "Item 11", "Item 12" }));
        jPanel1.add(jComboBox4);

        jComboBox3.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 13", "Item 14", "Item 15", "Item 16" }));
        jPanel1.add(jComboBox3);

        jComboBox5.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 17", "Item 18", "Item 19", "Item 20" }));
        jPanel1.add(jComboBox5);

        jComboBox6.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 21", "Item 22", "Item 23", "Item 24" }));
        jPanel1.add(jComboBox6);

        jComboBox7.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 25", "Item 26", "Item 27", "Item 28" }));
        jPanel1.add(jComboBox7);

        jComboBox8.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Item 29", "Item 30", "Item 31", "Item 32" }));
        jPanel1.add(jComboBox8);

        getContentPane().add(jPanel1, java.awt.BorderLayout.CENTER);

        jPanel2.setLayout(new java.awt.BorderLayout());
        jPanel2.add(jTextField1, java.awt.BorderLayout.CENTER);

        jButton1.setText("jButton1");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                // whats todo
            }
        });
        jPanel2.add(jButton1, java.awt.BorderLayout.LINE_END);

        getContentPane().add(jPanel2, java.awt.BorderLayout.PAGE_END);

        pack();
    }
}

那么，如果用户类型 4，combo1 到 combo4 将是 enabled，另一个将是 disabled，如何在 Button 侦听器上实现它？

Answer 1

我有多个这样的组合框：

JComboBox combo1 = new JComboBox();
JComboBox combo2 = new JComboBox();
JComboBox combo3 = new JComboBox();
JComboBox combo4 = new JComboBox();
JComboBox combo5 = new JComboBox();
JComboBox combo6 = new JComboBox();
JComboBox combo7 = new JComboBox();
JComboBox combo8 = new JComboBox();

每当我看到名为 foo1, foo2, foo3, ... 的变量时，我都会想，到底为什么编码器在这里不使用数组或 ArrayList？我问你同样的问题——你为什么要让自己的事情变得不必要地困难？

如果你创建了一个 JComboBoxes 的 ArrayList--

List<JComboBox<String>> combos = new ArrayList<>();
// code goes here to add 8 JComboBoxes to the list

然后，如果您的用户选择了选项 4 并将其放入变量索引中，您可以通过以下方式轻松禁用除第 4 个 JComboBox 之外的所有内容：

// first disable all the combos
for (JComboBox<String> comboBox : combos) {
    comboBox.setEnabled(false);
}
combos.get(index - 1).setEnabled(true);  // enable the selected combo

我使用index - 1，因为列表和数组是基于 0 的，而 ArrayList 中的第 4 个 JComboBox 位于索引 3。

但其他问题比比皆是：JTextField 几乎不应该添加 KeyListener，因为这会破坏它们的基本功能。考虑将 DocumentListener 添加到其 Document 或 DocumentFilter 甚至更好，使用 JSlider 或 JSpinner 以允许您将组件限制为仅允许可接受的输入？然后使用 ChangeListener。但更重要的是，你的设计很糟糕。为什么不简单地拥有一个 JComboBox 并在适当的事件发生时交换其数据模型？

如果您使用了一个填充了整数的 JSpinner，您可以向它添加一个更改侦听器，该侦听器将为单个 JComboBox 选择适当的数据模型，您的代码会更简单，对用户来说更白痴，最重要的是，更容易进行调试和增强。

例如

import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class Foo2 extends JPanel {
    private static final int MIN_VALUE = 1;
    private static final int MAX_VALUE = 8;

    private JSpinner spinner = new JSpinner(new SpinnerNumberModel(MIN_VALUE, MIN_VALUE, MAX_VALUE, 1));
    private List<DefaultComboBoxModel<String>> models = new ArrayList<>();
    private JComboBox<String> comboBox = new JComboBox<>();

    public Foo2() {
        for (int i = MIN_VALUE; i <= MAX_VALUE; i++) {
            DefaultComboBoxModel<String> comboModel = new DefaultComboBoxModel<>();
            for (int j = 0; j < 5; j++) {
                String element = String.format("Selection: %d, Item: %d", i, j);
                comboModel.addElement(element);
            }
            models.add(comboModel);
        }
        comboBox.setModel(models.get(0));

        spinner.addChangeListener(new ChangeListener() {

            @Override
            public void stateChanged(ChangeEvent e) {
                int selection = (int) spinner.getValue();
                comboBox.setModel(models.get(selection - 1));
            }
        });

        add(new JLabel("Selection:"));
        add(spinner);

        add(new JLabel("Combo:"));
        add(comboBox);
    }

    private static void createAndShowGui() {
        Foo2 mainPanel = new Foo2();

        JFrame frame = new JFrame("Foo2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}