Question

我有一个JFileChooser，它从目录中选择一个文件（我使用openCSV）并将数据填充到JTable中。

public class SelectFileButtonHandler{
//...
public SelectFileButtonHandler(FileReaderWindow fileReaderWindow) {
    this.fileReaderWindow = fileReaderWindow;
    this.fileChooser = new JFileChooser();
    this.fileHandler = new FileHandler();
}

public boolean isFileSelected(){ return (this.result==JFileChooser.APPROVE_OPTION); }

/**
 * returns the file's absolute path in a String object
 * @return String
 */
public String getCurrentFilePath(){return this.currentFilePath;}

public String getFileType(){
    return getFileName().substring(getFileName().lastIndexOf("."), getFileName().length());
}

public String getLastFilePath(){return this.lastFilePath;}

/**
 * Sets the file by defining the path
 * @param path 
 */
public void setFile(String path){this.file = new File(path);}

public void handleCommand() {
    this.fileHandler.readFile();
    this.fileReaderWindow.setRowData(fileHandler.getFileData());
    this.fileReaderWindow.setDataDemoTable(fileReaderWindow.getRowData());
    this.fileReaderWindow.setDataDemoTableC2(fileReaderWindow.getRowData());
    this.fileHandler.closeFile();
}

@Override
public void actionPerformed(ActionEvent event) {
    try{
        if(event.getActionCommand().equalsIgnoreCase("Προσθήκη αρχείου")){
            openFileDialog();
            if(isFileSelected()){
                setCurrentFilePath(this.fileChooser.getSelectedFile().getAbsolutePath());
                setLastFilePath(getCurrentFilePath());
                this.fileHandler.openFile(getCurrentFilePath());
                handleCommand();
            }
        }
        else {
            nextInChain.actionPerformed(event);
        }   
    }
    catch(Exception exception){
        JOptionPane.showMessageDialog(null, exception.getMessage(), null, JOptionPane.ERROR_MESSAGE);
    }
}

public void openFileDialog(){
    FileNameExtensionFilter filter = new FileNameExtensionFilter("txt", "txt", "txt");
    this.fileChooser.setFileFilter(filter);
    this.result = fileChooser.showOpenDialog(null); 
}

public void setCurrentFilePath(String currentFilePath){this.currentFilePath = currentFilePath;}
public void setLastFilePath(String lastFilePath){this.lastFilePath = lastFilePath;}
}

FileHandler.java

public class FileHandler{

 /**
 * Opens file located to the specific path
 * Path is absolute
 * @param path 
 */
public void openFile(String path) {setFileInputStream(path);}

/**
 * Reads data from file. 
 * Data are separated by split character selected by combo box.
 */
public void readFile() {
    try {
        setUTF8_CHARSET();
        setInputStreamReader(getFileInputStream(), getUTF8_CHARSET());
        setCSVReader(getInputStreamReader(),      this.fileReaderWindow.getSplitChoose().getSelectedItem().toString().charAt(0));
        setFileData(getCSVReader().readAll());
    } 
    catch (IOException ex) {
        Logger.getLogger(FileHandler.class.getName()).log(Level.SEVERE, null, ex);
    }
    catch(java.lang.NoClassDefFoundError err){
        JOptionPane.showMessageDialog(null, err.toString(), null, JOptionPane.ERROR_MESSAGE); 
    }
}

public void setCSVReader(InputStreamReader inputStreamReader, char separator){
    this.csvReader = new CSVReader(inputStreamReader, separator);
}

public void setFileData(List<String[]> fileData){this.fileData = fileData;}

public void setFileInputStream(String path){
     try{
        this.fileInputStream = new FileInputStream(path); 
    }
    catch(FileNotFoundException exception){
        JOptionPane.showMessageDialog(null, "Το αρχείο δε βρέθηκε στο δίσκο.\nΠαρακαλώ, ξαναπροσπαθήστε.", null, JOptionPane.ERROR_MESSAGE);
    }
}

public void setInputStreamReader(FileInputStream fileInputStream, CharsetDecoder UTF8_CHARSET){
    this.inputStreamReader = new InputStreamReader(fileInputStream, UTF8_CHARSET);
}

}

我的问题是，当我尝试从另一个类调用getLastFilePath时，我得到null而不是路径

public class SplitChooseComboHandler implements ItemListener{
private FileReaderWindow fileReaderWindow;
private FileHandler fileHandler;
private SelectFileButtonHandler selectFileButtonHandler;

@Override
public void itemStateChanged(ItemEvent e) {
   if (e.getStateChange() == ItemEvent.SELECTED) {
      this.fileReaderWindow = new FileReaderWindow();
      this.selectFileButtonHandler = new SelectFileButtonHandler(fileReaderWindow);
      this.fileHandler.openFile(selectFileButtonHandler.getLastFilePath());
      this.selectFileButtonHandler.handleCommand();
      JOptionPane.showMessageDialog(null, "file path is: " + this.selectFileButtonHandler.getLastFilePath(), null, JOptionPane.INFORMATION_MESSAGE);
   }
}
}

有人可以解释为什么会这样吗？提前谢谢

Answer 1

有文件lastFilePath = new File 并在您的文件处理程序中

    public static void LastFile{
        lastFilePath = (File)selectFileButtonHandler.getLastFilePath();
    }

并在您的splitChooseComboHandler中用LastFilePath替换selectFileButtonHandler.getLastFilePath（）检查是否有效哈哈

Answer 2

看看你的代码......

// Create a new instance of SelectFileButtonHandler
this.selectFileButtonHandler = new SelectFileButtonHandler(fileReaderWindow);
this.fileHandler.openFile(selectFileButtonHandler.getLastFilePath());

在致电getLastFilePath时，值lastFilePath为null

lastFilePath的值仅由setLastFilePath方法更改，但仅由actionPerformed中的SelectFileButtonHandler方法调用。

这意味着当值path值传递给setFileInputStream中的FileHandler方法时，它是null ...

您可以考虑lastFilePath null的可能性，并提供默认值，例如用户的主目录...

JFileChooser丢失了最后一个文件路径

2 个答案: