JComboBox 动态更新值答案

【问题标题】：JComboBox dynamically updating valuesJComboBox 动态更新值
【发布时间】：2015-06-13 18:07:58
【问题描述】：

我正在尝试使用 xml 节点更新组合框的项目，我在运行循环时获取了节点，但是不知何故我无法将它们添加为 ComboBox 的项目

public class XMLtoExcelGUI extends javax.swing.JFrame {

    public  java.io.File file;

    public XMLtoExcelGUI() {
        initComponents();
    }
    public void  setProgressBarValue(String s){

        jProgressBar1.setString(s);

    }

    @SuppressWarnings("unchecked")

    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jButton1 = new javax.swing.JButton();
        jLabel2 = new javax.swing.JLabel();
        jProgressBar1 = new javax.swing.JProgressBar();
        jButton3 = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextPane1 = new javax.swing.JTextPane();
        jComboBox1 = new javax.swing.JComboBox();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setText("XMLToExcel");

        jButton1.setText("Choose File");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jLabel2.setText("Select Measures");

        jProgressBar1.setStringPainted(true);

        jButton3.setText("Get Measure Data");

        jScrollPane1.setViewportView(jTextPane1);

        jComboBox1.setMaximumRowCount(30);
        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] {}));

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(137, Short.MAX_VALUE)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 97, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(127, 127, 127))
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addComponent(jProgressBar1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(117, 117, 117))))
            .addGroup(layout.createSequentialGroup()
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jButton3)
                        .addGap(0, 0, Short.MAX_VALUE))
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 95, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 95, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGap(27, 27, 27)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jScrollPane1)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(0, 0, Short.MAX_VALUE)))))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 46, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jButton1)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 65, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(63, 63, 63)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(28, 28, 28)
                .addComponent(jButton3)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 26, Short.MAX_VALUE)
                .addComponent(jProgressBar1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

        final JFileChooser  fileDialog = new JFileChooser();
        int returnVal = fileDialog.showOpenDialog(this);
            if (returnVal == JFileChooser.APPROVE_OPTION) {
            file = fileDialog.getSelectedFile();

            TestVDT call = new TestVDT(file);
            jTextPane1.setText(file.toString());

            }          

    }                                        

    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(XMLtoExcelGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }

        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new XMLtoExcelGUI().setVisible(true);
            }
        });
    }


    public javax.swing.JButton jButton1;
    public javax.swing.JButton jButton3;
    public javax.swing.JComboBox jComboBox1;
    public javax.swing.JLabel jLabel1;
    public javax.swing.JLabel jLabel2;
    public javax.swing.JProgressBar jProgressBar1;
    public javax.swing.JScrollPane jScrollPane1;
    public javax.swing.JTextPane jTextPane1;
    // End of variables declaration                   
}

public class TestVDT {

    public int setNumberOfMeasures = 0;
    public String[]  Measures = new String[30];

    public void setMeasureValues(String S[], int length) {
        Vector comboBoxItems = new Vector();
        for (int i = 1; i < length; i++) {
            comboBoxItems.add(S[i]);
        //    System.out.println(S[i]);
        }
         XMLtoExcelGUI call = new XMLtoExcelGUI();
         DefaultComboBoxModel defaultComboBoxModel = new DefaultComboBoxModel(comboBoxItems);

        call.jComboBox1.setModel(defaultComboBoxModel);



    }

    public TestVDT(java.io.File FName) {

        try {
            File f = new File(FName.toString());
            FileInputStream fis = new FileInputStream(f);
            byte[] ba = new byte[(int) f.length()];
            fis.read(ba);
            VTDGen vg = new VTDGen();
            vg.setDoc(ba);
            vg.parse(false);
            VTDNav vn = vg.getNav();

            FileOutputStream fout = new FileOutputStream("E:\\Data.xls");

            HSSFWorkbook workbook = new HSSFWorkbook();
            HSSFSheet worksheet = workbook.createSheet("Data");

            Row row1 = worksheet.createRow(0);
            row1.createCell(0).setCellValue("Measure_id");
            row1.createCell(1).setCellValue("Denominator");
            row1.createCell(2).setCellValue("Numerator");
            row1.createCell(3).setCellValue("exclusion");
            row1.createCell(4).setCellValue("performance criteria");

            //for(int i=0;i<3;i++)
            int rowIndex = 1;
            int j = 1;
            vn.toElement(VTDNav.FIRST_CHILD);
            do {

                if (vn.matchElement("practice_data")) {
                    vn.toElement(VTDNav.FIRST_CHILD);
                }
                if (vn.matchElement("provider_data")) {
                    vn.toElement(VTDNav.FIRST_CHILD);
                }

                if (vn.matchElement("provider_identification")) {
                    vn.toElement(VTDNav.FIRST_CHILD);

                }
                if (vn.matchElement("measure")) {
                    vn.toElement(VTDNav.FIRST_CHILD);
                    do {
                        Row row = worksheet.createRow(rowIndex++);
                        int cellIndex = 0;

                       String temp = vn.toString(vn.getAttrVal("measure_id"));
                        System.out.println(temp);

                        Measures[j] = temp;
                        row.createCell(cellIndex++).setCellValue(vn.toString(vn.getAttrVal("measure_id")));
                        System.out.print(" -- ");

                        System.out.print(vn.toString(vn.getAttrVal("denominator")));
                        row.createCell(cellIndex++).setCellValue(vn.toString(vn.getAttrVal("denominator")));

                        System.out.print(" -- ");

                        System.out.print(vn.toString(vn.getAttrVal("numerator")));
                        row.createCell(cellIndex++).setCellValue(vn.toString(vn.getAttrVal("numerator")));

                        System.out.print(" -- ");

                        System.out.print(vn.toString(vn.getAttrVal("exclusion")));
                        row.createCell(cellIndex++).setCellValue(vn.toString(vn.getAttrVal("exclusion")));
                        System.out.print(" -- ");

                        System.out.println(vn.toString(vn.getAttrVal("performance_rate")));
                        row.createCell(cellIndex++).setCellValue(vn.toString(vn.getAttrVal("performance_rate")));
                        setNumberOfMeasures++;
                        j++;
                    } while (vn.toElement(VTDNav.NEXT_SIBLING));

                }

            } while (vn.toElement(VTDNav.NEXT_SIBLING));

            System.out.println(setNumberOfMeasures);
            workbook.write(fout);
            fout.flush();

            setMeasureValues(Measures, setNumberOfMeasures);
        } catch (Exception e) {
            System.out.println("exception occurred ==>" + e);
        }
    }

    @SuppressWarnings("empty-statement")
    public static void main(String[] args) {

    }

}

默认情况下，Jcombo 框的值是空白的，当调用 setMeasureValues() 函数时，它应该更新组合框的项目，但不是

【问题讨论】：

标签： java swing jcombobox

【解决方案1】：

您的 XMLtoExcelGUI 变量 call 是 setMeasureValues(...) 方法的本地变量。对其引用的对象所做的任何更改都只会反映在此本地对象中，而不会反映在任何其他类似类型的对象中。一个猜测，但也许您希望将对显示的 XMLtoExcelGUI 对象的有效引用传递给该方法。否则，如果这没有帮助，您可能不得不通过讲述和展示更多内容来改进您的问题。

是的，我是对的——您正在一个完全不同的非显示 XMLtoExcelGUI 实例中设置组合框的模型。更改一个实例的状态不会也不应该对另一个实例产生影响。解决办法是改变正确显示实例的状态。

改变这个：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

    final JFileChooser  fileDialog = new JFileChooser();
    int returnVal = fileDialog.showOpenDialog(this);
        if (returnVal == JFileChooser.APPROVE_OPTION) {
        file = fileDialog.getSelectedFile();

        TestVDT call = new TestVDT(file);  
        jTextPane1.setText(file.toString());

        }          

}

到这样的事情：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

    final JFileChooser  fileDialog = new JFileChooser();
    int returnVal = fileDialog.showOpenDialog(this);
        if (returnVal == JFileChooser.APPROVE_OPTION) {
        file = fileDialog.getSelectedFile();

        TestVDT call = new TestVDT(this, file);  // ****** changed
        jTextPane1.setText(file.toString());

        }

然后这个

public class TestVDT {

    public int setNumberOfMeasures = 0;
    public String[]  Measures = new String[30];

    public TestVDT(java.io.File FName) {

类似于：

public class TestVDT {

    public int setNumberOfMeasures = 0;
    public String[]  Measures = new String[30];
    private XMLtoExcelGUI gui;

    public TestVDT(XMLtoExcelGUI gui, java.io.File FName) {
        this.gui = gui;

这样您的方法可以使用对实际显示的 GUI 的引用：

public void setMeasureValues(String S[], int length) {
    Vector comboBoxItems = new Vector();
    for (int i = 1; i < length; i++) {
        comboBoxItems.add(S[i]);
    }

    //  XMLtoExcelGUI call = new XMLtoExcelGUI(); // **** no!
     DefaultComboBoxModel defaultComboBoxModel = new DefaultComboBoxModel(comboBoxItems);

    // give XMLtoExcelGUI a public method that sets 
    // its own combo box's model
    gui.setComboModel(defaultComboBoxModel);



}

【讨论】：

所以 XMLtoExcelGUI 是一个不同的 java 文件，其中声明了组合框，gui 首先要求解析 xml 文件，它调用主逻辑构造函数，构造函数解析 xml 文件并获取节点并传递setMeasureValues() 函数中的值，该函数获取节点并应该更新组合框的项目，但最后一部分是我卡住的地方。
@BhavikPatel：请更新您的问题，告诉我们更多您的程序结构，XMLtoExcelGUI 类在哪里，此代码与此类相关的位置等...请帮助我们更全面地了解您的代码，更全面地了解您的问题。