java JFileChooser存储用户选择的文件

Question

我在和Swing一起工作。我想抓取用户选择的文件，并在用户按下计数按钮时使用它们来计数。然而，当我按下按钮时，即使我选择了文件，也会出现空指针。如何让它工作

      class  RefractiveGUIFrame extends JFrame 
{

    private static final int DEFAULT_WIDTH = 300;
    private static final int DEFAULT_HEIGHT = 200;
    private File[] dataFiles;

    private Object[][] refractiveIndex = null;




    public RefractiveGUIFrame()
    {
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
        setLocationByPlatform(true);


        final JPanel northPanel = new JPanel();
        final JPanel westPanel = new JPanel();
        northPanel.setLayout(new GridLayout(2,3));
        westPanel.setLayout(new GridLayout(3,1));


    //create components northPanel
        final JButton fileBrowseButton = new JButton("Browse..");
        final JTextField fileTextField = new JTextField(100);
        final JButton directoryBrowseButton = new JButton("Browse..");
        final JTextField directoryTextField = new JTextField(100);
        final JRadioButton fileChooser = new JRadioButton ("Choose File..",false);
        final JRadioButton directoryChooser = new JRadioButton ("Choose Directory..",true);         

        //resposible for turning off the previously set button
        ButtonGroup group = new ButtonGroup();
        group.add(fileChooser);
        group.add(directoryChooser);

        //set browse button off
        fileBrowseButton.setEnabled(false);
        directoryBrowseButton.setEnabled(true);

    //create components westPanel
        final JButton countButton = new JButton ("Count");
        final JButton displayButton = new JButton ("Display");
        final JButton saveButton = new JButton ("Save");

    //add components northPanel         
        northPanel.add(directoryChooser);
        northPanel.add(fileTextField);          
        northPanel.add(directoryBrowseButton);
        northPanel.add(fileChooser);
        northPanel.add(directoryTextField);
        northPanel.add(fileBrowseButton);

    //add components westPanel
        westPanel.add(countButton);
        westPanel.add(displayButton);
        westPanel.add(saveButton);

    //add panels to frame
        this.add(northPanel, BorderLayout.NORTH);
        this.add(westPanel, BorderLayout.WEST);

    //create file dialog that will be used in listeners
        final JFileChooser chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File ("."));

    //add action listeners as anonymous innner classes


        fileChooser.addActionListener(new ActionListener()
        {           
            public void actionPerformed(ActionEvent e)
            {
                fileBrowseButton.setEnabled(true);
                directoryBrowseButton.setEnabled(false);

            }
        });

        directoryChooser.addActionListener(new ActionListener()
        {           
            public void actionPerformed(ActionEvent e)
            {
                fileBrowseButton.setEnabled(false);
                directoryBrowseButton.setEnabled(true);

            }
        });



        fileBrowseButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                chooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
                int returnVal = chooser.showOpenDialog(northPanel);
                dataFiles = chooser.getSelectedFiles();
                String filename = chooser.getSelectedFile().getPath();
                fileTextField.setText(filename);
            }
        });


        directoryBrowseButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                chooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
                int returnVal = chooser.showOpenDialog(northPanel);     
                String filename = chooser.getSelectedFile().toString();
                fileTextField.setText(filename);
                dataFiles = chooser.getSelectedFile().listFiles();
                for (File f : dataFiles)
                    System.out.println(f);


            }
        });

        countButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                try{
                    for (int i =0; i<dataFiles.length;i++)
                    {
                        RefractiveIndex ri = new RefractiveIndex(dataFiles[i]);
                        refractiveIndex[i][i] = ri;
                        System.out.println("Refractive index value : " + ri.rii.toString());
                    }
                }
                catch (Exception e1) {
                        e1.printStackTrace();
                    }
                }
            }); //end countButton actionListener
        }
}

我使用以下命令编辑代码：

chooser.addPropertyChangeListener(new PropertyChangeListener() {
              public void propertyChange(PropertyChangeEvent evt) {
                if (JFileChooser.SELECTED_FILES_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
                  JFileChooser chooser = (JFileChooser) evt.getSource();

                  dataFiles = (File[])evt.getNewValue();

                  // Get list of selected files
                  dataFiles = chooser.getSelectedFile().listFiles();
                 // for (File f : dataFiles)
                //    System.out.println(f);
                }    
              }
            });

现在我有一个错误

      java.lang.NullPointerException
at com.refractiveindex.RefractiveGUIFrame$6.actionPerformed(RefractiveGUITest.java:230)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

我认为这是折射索引类中的一个错误。你也这么认为吗？我想调试它，但我不知道如何进入类内部并在RefractiveIndex类中调试

我添加折射索引类。也许这会有帮助，因为我不知道如何解决它。实际上，当我运行它时，它会打印System.out.println(entry.getKey())行，但我不知道它停在哪里，为什么停下来

public class RefractiveIndex {

public static Double sumRaMw = 0.0; 
public static Double sumMw = 0.0;
public static Double sumPsvMw = 0.0; 
public static Double rii;
File f = new File  ("DATA.txt");


//public static void main(String[] args) throws Exception {
    //String f = "DATA.txt";
    //String fasta = "3LWK.fasta.txt";
    //HashMap<String,ArrayList<Double>> myMap = readDataFromTxt(f);
    //System.out.println(myMap.keySet());
    //System.out.println(myMap.values());
    //System.out.println(myMap.get("PHE"));
    //ArrayList<ProteinSequence> seq = new ArrayList<ProteinSequence>();
    //seq = getProteinSequenceFromFasta(fasta);
    //Double refractive = calculateRefractive(myMap, seq);
    //System.out.println(refractive.toString());

//}

public RefractiveIndex(File fastaFile) throws Exception{
    HashMap<String,ArrayList<Double>> DataMap = readDataFromTxt(f);
    //HashMap<String,ArrayList<Double>> myMap = readDataFromTxt(fastaFile);
    ArrayList<ProteinSequence> seq = new ArrayList<ProteinSequence>();
    seq = getProteinSequenceFromFasta(fastaFile.getAbsolutePath());
    Double refractive = calculateRefractive(DataMap, seq);

}
public static HashMap<String,ArrayList<Double>> readDataFromTxt (File fileName) throws NumberFormatException, IOException
{
    HashMap<String, ArrayList<Double>> map = new HashMap<String, ArrayList<Double>>();


    FileReader fr = new FileReader(fileName); //read characters
    BufferedReader br = new BufferedReader (fr); //read line
    String line;
    while ((line = br.readLine())!=null)
    {
        ArrayList<Double> values = new ArrayList<Double>();
        String parts[] = line.split("\t");
        values.add(Double.parseDouble(parts[3]));
        values.add(Double.parseDouble(parts[4]));
        values.add(Double.parseDouble(parts[2]));
        String key = parts[1];


        map.put(key, values);


    }
    return map;
}

public static Double calculateRefractive (HashMap<String, ArrayList<Double>> hm, ArrayList<ProteinSequence> seq)
{
    for (ProteinSequence s : seq){
        List<AminoAcidCompound> compound = s.getAsList();
        for (int i =0;i<compound.size();i++){
            ArrayList<Double> temp = hm.get(compound.get(i).toString());
            sumMw += temp.get(0);
            //System.out.println(sumMw.toString());
            sumRaMw += temp.get(1)*temp.get(0);
            //System.out.println(temp.get(2));
            sumPsvMw +=temp.get(2)*temp.get(0);
            }
    }
    Double rp = sumRaMw/sumMw;
    Double vp = sumPsvMw/sumMw;
    Double np = Math.sqrt((2 * rp + vp)/(vp - rp));
    Double no = 1.3340 + (1.3325 - 1.3330);
    rii = 1.5 * vp * no * (np * np - no * no)/(np * np + 2 * no * no);
    return rii;

}

public static ArrayList<ProteinSequence> getProteinSequenceFromFasta(String file) throws Exception{

    LinkedHashMap<String, ProteinSequence> a = FastaReaderHelper.readFastaProteinSequence(new File(file));
    ArrayList<ProteinSequence> sequence =  new ArrayList<ProteinSequence>(a.values());
    for (Map.Entry<String, ProteinSequence> entry : a.entrySet()){
        System.out.println(entry.getKey());
    }
    return sequence;

}

}

Answer 1

在我看来directoryBrowseButton的ActionListener是在单击浏览按钮并且没有选择的文件时触发的。然后，当您启动计数按钮时，dataFiles为空

您应该侦听处理文件浏览器中项目选择的事件，并将其指定给数据文件

chooser.addPropertyChangeListener(new PropertyChangeListener() {
    public void propertyChange(PropertyChangeEvent evt) {
       if (JFileChooser.SELECTED_FILES_CHANGED_PROPERTY.equals(
               evt.getPropertyName())) {
           JFileChooser chooser = (JFileChooser)evt.getSource();
           dataFiles = (File[])evt.getNewValue();
       }
    }
});