java JFileChooser和复制文件

Question

我正在做课堂作业，有几个问题我希望能得到帮助。分配是一个GUI，允许用户选择要复制的文件，并选择要将文件复制到的位置

我已经完成了作业，但有几件事我想看看是否可以改变

选择源文件时，我只想在标签中显示源文件的名称，但程序需要完整的路径来复制文件，每次我试图将其切换为仅显示文件名时，程序都不会运行，因为它不知道文件位于何处。第二个问题，是否有办法让程序自动复制一个文件作为一个文件。bak文件。。。假设源文件是一个文本文件，用户选择一个目标文件夹，点击“复制”按钮，它会保存一个同名的文件，但不是一个文本文件。bak分机

我把有问题的代码放在***和***之间，留下我试图用来显示文件名的代码，并将其注释掉。谢谢你的帮助

public class CopyFile extends JFrame{

private JFileChooser fc;
private JButton copyButton;
private JButton chooseFileButton;
private JButton destinationButton;
private File workingDirectory;
private JLabel sourceLabel;
private JLabel destinationLabel;
private JTextField sourceText;
private JTextField sourceFileText;
private JTextField destinationText;

public static void main(String [] args) {
    CopyFile go = new CopyFile();
    go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    go.setSize(500, 150);
    go.setVisible(true);
}

public CopyFile() {
    super("Copy a text file");
    setLayout(new GridLayout(3, 3, 5, 5));
    fc = new JFileChooser();

    //Open dialog box inside project folder to make easier to find files
    workingDirectory = new File(System.getProperty("user.dir"));
    fc.setCurrentDirectory(workingDirectory);
    //create labels and buttons for window
    chooseFileButton = new JButton("CHOOSE SOURCE FILE");
    destinationButton = new JButton("DESTINATION FOLDER");
    copyButton = new JButton("COPY FILE");      
    sourceLabel = new JLabel("SOURCE FILE: ");
    sourceText = new JTextField(10);
    sourceText.setEditable(false);
    destinationLabel = new JLabel("DESTINATION: ");
    destinationText = new JTextField(10);

    //add everything to JFrame  
    add(sourceLabel);
    add(sourceText);
    add(chooseFileButton);  
    add(destinationLabel);
    add(destinationText);
    add(destinationButton);
    add(copyButton);

    //Create TheHandler object to add action listeners for the buttons.
    TheHandler handler = new TheHandler();
    chooseFileButton.addActionListener(handler);
    destinationButton.addActionListener(handler);
    copyButton.addActionListener(handler);
}

//Inner class to create action listeners    
private class TheHandler implements ActionListener {
    public void actionPerformed(ActionEvent event) {
        int returnVal;
        String selectedFilePath;
        File selectedFile;

******************************************************************************      
        //Selecting a source file and displaying what the user is doing.
        if(event.getSource() == chooseFileButton) {     
            returnVal = fc.showOpenDialog(null);
            //Set the path for the source file. 
            if(returnVal == JFileChooser.APPROVE_OPTION) {  

  /*The two next lines of code are what I was trying to do to get only the
  file name but I get a whole page of errors, mainly I think it's saying no 
  such file exists*/
                //selectedFile = fc.getSelectedFile();
                //sourceText.setText(selectedFile.getName());   
                selectedFilePath = fc.getSelectedFile().getAbsolutePath();
                sourceText.setText(selectedFilePath);
            }       
        }//end if

******************************************************************************          
        //Handle destination button.
        if(event.getSource() == destinationButton) {
            returnVal = fc.showSaveDialog(null);
            if(returnVal == JFileChooser.APPROVE_OPTION) {
                 selectedFilePath = fc.getSelectedFile().getAbsolutePath();
                destinationText.setText(selectedFilePath);
            }               
        }//end if

        //Handle copy button
        if(event.getSource() == copyButton) {
            File sourceFile = new File(sourceText.getText());
            File destinationFile = new File(destinationText.getText());
            Path sourcePath = sourceFile.toPath();
            Path destinationPath = destinationFile.toPath();        
            try {
                Files.copy(sourcePath,  destinationPath);
            } catch (IOException e) {
                e.printStackTrace();
            }   
        }//end if

    }//end actionPerformed      
}//end TheHandler class
}//end class

Answer 1

You have to keep the source and destination file paths as Files, not Strings. Modify your code of TheHandler class as follows.

1. 添加selectedSourceFile和selectedDestinationFile本地字段

   private class TheHandler implements ActionListener {
       private File selectedSourceFile;
       private File selectedDestinationFile;
   

2. 选择文件时更新它们，并设置文件名而不是文本字段的路径

源文件按钮

        if (event.getSource() == chooseFileButton) {
            returnVal = fc.showOpenDialog(null);
            if (returnVal == JFileChooser.APPROVE_OPTION) {
                selectedSourceFile = fc.getSelectedFile();
                sourceText.setText(selectedSourceFile.getName());
            }
        }

目的地按钮

        if (event.getSource() == destinationButton) {
            returnVal = fc.showSaveDialog(null);
            if (returnVal == JFileChooser.APPROVE_OPTION) {
                selectedDestinationFile = fc.getSelectedFile();
                destinationText.setText(selectedDestinationFile.getName());
            }
        }

1. 复制时使用selectedSourceFile和selectedDestinationFile

       if (event.getSource() == copyButton) {
           Path sourcePath = selectedSourceFile.toPath();
           Path destinationPath = selectedDestinationFile.toPath();
           try {
               Files.copy(sourcePath, destinationPath);
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   

Now you are done the first requirement. You can make backfile when selecting the destination file. So, add your code to make backup file when selecting destination button.

        if (event.getSource() == destinationButton) {
            returnVal = fc.showSaveDialog(null);
            if (returnVal == JFileChooser.APPROVE_OPTION) {
                selectedDestinationFile = fc.getSelectedFile();
                destinationText.setText(selectedDestinationFile.getName());

                //copy backup
                String name = selectedSourceFile.getName();
                name = selectedSourceFile.getName().substring(0, name.lastIndexOf(".")) + ".bak";
                File destinationFile = new File(selectedDestinationFile.getParentFile(), name);
                try {
                    Files.copy(selectedSourceFile.toPath(), destinationFile.toPath());
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }

Answer 2

When selecting the the source file I want ONLY the name of the source file to show up in the Label but, the program needs the entire path in order to copy the file and every time I tried to switch it to show the file name only the program won't run because it doesn't know where the file is located.

可以使用File#getName，它将返回文件名并将其用作标签的文本，但保留对原始File的引用。您不应该使用标签文本来生成新的File引用，只需保留对源File和目标File以及实例字段的引用

Second question, is there anyway to make the program copy a file automatically as a .bak file...Say the source file is a text file and the user picks a destination folder and hits copy and it saves a file with the same name but a .bak extension?

String name = selectedFile.getName();
name = name.substring(0, name.lastIndexOf("."));
name += ".bak";
File destinationFile = new File(destinationPath, name);

将selectedFile的扩展名更改为.bak，但是您可能应该添加一个检查，看看它是否有一个扩展名