Reading a txt file in a Java GUI

问题

All I want to do is display the entire contents of a txt file. How would I go about doing this? I'm assuming that I will set the text of a JLabel to be a string that contains the entire file, but how do I get the entire file into a string? Also, does the txt file go in the src folder in Eclipse?

回答1:

This code to display the selected file contents in you Jtext area

      static void readin(String fn, JTextComponent pane) 
              {
             try 
              {
               FileReader fr = new FileReader(fn);
               pane.read(fr, null);
               fr.close();
              }
                 catch (IOException e) 
                 {
                  System.err.println(e);
                 }
              }

To choose the file

         String cwd = System.getProperty("user.dir");
         final JFileChooser jfc = new JFileChooser(cwd);

            JButton filebutton = new JButton("Choose");
            filebutton.addActionListener(new ActionListener() 
            {
            public void actionPerformed(ActionEvent e) 
            {
                if (jfc.showOpenDialog(frame) !=JFileChooser.APPROVE_OPTION)

                        return;
                  File f = jfc.getSelectedFile();



            readin(f.toString(), textpane);

                  SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        frame.setCursor(Cursor.
                            getPredefinedCursor(
                            Cursor.DEFAULT_CURSOR));

                    }
                });
            }
        });

回答2:

All I want to do is display the entire contents of a txt file. How would I go about doing this? I'm assuming that I will set the text of a JLabel to be a string that contains the entire file but how do I get the entire file into a string?

You would be better of using a JTextArea to do this. You can also look at the read() method.

does the txt file go in the src folder in Eclipse?

Nope. You can read files from any where. The tutorial on "Reading, Writing, and Creating Files" would be a good place to start

回答3:

create text file in your project's working folder
read your text file line by line
store the line contents in stringBuilder variable
then append next line contents to stringBuilder variable
then assign the content of your StringBuilder variable to the JLabel's text property

But it is not good idea to store whole file's data into JLabel, use JTextArea or any other text containers.

Read your file like this:

BufferedReader br = new BufferedReader(new FileReader("file.txt"));
try {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
       line = br.readLine();
    }
    String everything = sb.toString();
} finally {
    br.close();
}

now assign value of everything to JLabel or JTextArea