第二个组合框中的选项依赖于第一个组合框 [英] Options in second comboBox dependent on first comboBox

问题描述

可能的重复:
动态 JComboBoxes
如何通过使用控制组合框另一个组合框摆动

    // model drop-down      
    final JComboBox modelName = new JComboBox();
    modelName.addItem("Choose One...");
    modelName.addItem("Hypercom");
    modelName.addItem("Deja Voo");
    modelName.addItem("Nurit");
    modelName.addItem("Verifone");
    int modelIndex = modelName.getSelectedIndex();      

    modelPanel.add(modelName);

我在下面尝试做的是根据第一个中选择的内容更改第二个组合框的选项......但它没有这样做.无论我在顶部的组合框中选择什么，第二个的选项都不会改变......我错过了什么?

What I'm trying to do below is have the options on the second comboBox change depending on what was selected in the first... but it's not doing it. No matter what I select in the top comboBox, the options for the second don't change... what am I missing?

            // Terminal Panel (within Panel1)
    JPanel termPanel = new P(15);
    termPanel.setBackground(Color.WHITE);
    panel1.add(termPanel);

    final JComboBox termName = new JComboBox();

    if (modelIndex == 1) {              
        termName.addItem("Choose One...");
        termName.addItem("T7Plus");
        termName.addItem("4205");
        termName.addItem("4210");
        termName.addItem("4220");           

    } else if (modelIndex == 2) {           
        termName.addItem("Choose One...");
        termName.addItem("M-3");
        termName.addItem("X-5");
        termName.addItem("X-8");
        termName.addItem("V Series");

    } else if (modelIndex == 3) {
        termName.addItem("Choose One...");
        termName.addItem("2085");
        termName.addItem("3020/8320");
        termName.addItem("8400");
        termName.addItem("8000/8020");

    } else if (modelIndex == 4) {
        termName.addItem("Choose One...");
        termName.addItem("37 Dial");
        termName.addItem("37 IP");
        termName.addItem("VX Dial");
        termName.addItem("VX IP");

    } else {
        termName.addItem("Select Model Above");
    }

    termName.getSelectedIndex();
    termPanel.add(termName);

更新

我更新了代码，但现在我收到了一个空点异常错误......这是它的位置:

I updated the code, but now I'm getting a nullPoint Exception Error... here's where it's at:

    final DefaultComboBoxModel termModel = new DefaultComboBoxModel(new String[]{"Choose One...", "Hypercom", "DejaVoo", "Nurit", "Verifone"});

...

// model drop-down      
    modelName.setModel(termModel);  // NULLPOINT EXCEPTION HERE

    modelName.addActionListener (new ActionListener () {
        public void actionPerformed(ActionEvent e) {
            if ("Hypercom".equals(modelName.getSelectedItem())){
                termName.setModel(hSpecModel);    
            } else if ("Deja Voo".equals(modelName.getSelectedItem())){
                termName.setModel(dSpecModel);    
            } else if ("Nurit".equals(modelName.getSelectedItem())){
                termName.setModel(nSpecModel);
            } else if ("Verifone".equals(modelName.getSelectedItem())){
                termName.setModel(vSpecModel);
            } else {
                termName.setModel(slctAbove);
            }
        }
    });

    modelPanel.add(modelName);

推荐答案

您应该添加能够更改第二个 JComboBox 内容的 ActionListener.此外，您应该考虑在 Map 中链接模型名称和术语名称.请看我的例子:

You should add ActionListener which is able to changing content of second JComboBox. Additionally, you should think about linking model names and term names in Map. Please, see my example:

class TwoComboboxFrame extends JFrame {

    private static final long serialVersionUID = 1L;

    private Map<String, List<String>> modelNameTermName = new LinkedHashMap<String, List<String>>();

    private JComboBox<String> termNameComboBox;

    public TwoComboboxFrame() {
        init();
        buildDataModel();

        JPanel panel = createAndAddPanel();
        buildModelNameComboBox(panel);
        buildTermNameComboBox(panel);
    }

    private void buildTermNameComboBox(JPanel panel) {
        termNameComboBox = new JComboBox<String>();
        termNameComboBox.addItem("Select Model Above");
        panel.add(termNameComboBox);
    }

    private void buildModelNameComboBox(JPanel panel) {
        JComboBox<String> modelName = new JComboBox<String>();
        modelName.addItem("Choose One...");
        for (String value : modelNameTermName.keySet()) {
            modelName.addItem(value);
        }
        panel.add(modelName);
        modelName.addActionListener(new ActionListener() {

            @SuppressWarnings("unchecked")
            @Override
            public void actionPerformed(ActionEvent e) {
                JComboBox<String> source = (JComboBox<String>) e.getSource();
                String selectedValue = source.getSelectedItem().toString();
                List<String> termNames = modelNameTermName.get(selectedValue);
                termNameComboBox.removeAllItems();
                if (termNames == null) {
                    termNameComboBox.addItem("Select Model Above");
                } else {
                    termNameComboBox.addItem("Choose One...");
                    for (String name : termNames) {
                        termNameComboBox.addItem(name);
                    }
                }
            }
        });
    }

    private void buildDataModel() {
        modelNameTermName.put("Hypercom",
                Arrays.asList("T7Plus", "4205", "4210", "4220"));
        modelNameTermName.put("Deja Voo",
                Arrays.asList("M-3", "X-5", "X-8", "V Series"));
        //Add other data
    }

    private void init() {
        setTitle("Two comboboxex");
        setSize(300, 200);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
    }

    private JPanel createAndAddPanel() {
        JPanel panel = new JPanel(true);
        panel.setLayout(new GridLayout(1, 2));
        add(panel);
        return panel;
    }
}

用法示例:

public static void main(String[] args) throws Exception {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            TwoComboboxFrame ex = new TwoComboboxFrame();
            ex.setVisible(true);
        }
    });
}

这篇关于第二个组合框中的选项依赖于第一个组合框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！