如何仅使JTextArea（+ JScrollPane）的下一行可编辑

Question

So im creating a server, and that works great, however I am a bit stuck on the GUI. You see, I would like it to look just like Command Prompt, where only the next line is editable, and it does not let you delete any other text. So right now I have:

JTextArea ta = new JTextArea();
JScrollPane sp = new JScrollPane(ta);

Then the frame stuff...

    f.setTitle("Server");
    f.setBounds(ss.width - 600, 50, 550, 350);
    f.setResizable(false);
    f.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);//added window listener so closes socket connection first
    f.setAlwaysOnTop(true);

Then adding it:

    f.add(sc);
    jt.setBackground(Color.BLACK);
    jt.setForeground(Color.WHITE);
    //jt.setEditable(false);

Finally, the method I use to output to the TextArea:

public static void append(String text) {
    jt.append(text);
    jt.append("\n\n"+System.getProperty("user.name")+" / "+getIp()+" > ");
    jt.setCaretPosition(jt.getDocument().getLength());
}

Now I need to assign a String to what the user types into the JTextArea after they press enter:>?

jt.addActionListener(...{
    public void ActioEvent(ActionEvent e){
        String text = JTextArea.getLines().getLastLine().getText().replace(System.getProperty("user.name")+" / "+getIp()+"       > ", "");
    }
});

Maybe something like that? Then I need to have it so that only the part after the ">" is editable?

Answer 1

The way to do this is with a DocumentFilter . This is a fairly obscure and little-used part of Java, and is far from easy to use. However it allows you to insert a DocumentFilter between the UI (where rich text content is edited) and the underlying model (the content). You pass all the 'insert' and 'remove' operations through the filter, which can either accept, refuse or modify them. You can code the filter to only permit modifications to the command line, and not to the prompt.

As I say, this is a pretty hard piece of coding, and the Document/DocumentFilter structure has a lot of complexity that your particular application doesn't need. However it does provide you with the facilities you need.

There is a tutorial in the standard Java doc pages, but not an advanced one, and very few examples that I know of are out there on the web.

ProtectedTextComponent (thanks camickr) provides an example of how to do something similar.

Answer 2

Use a Collection a JTextField .
Let the user type on a JTextField , and once he presses enter , move the control to the next JTextField while making the above JTextField uneditable and also remove the JScrollPane from it.

Hope this helps.

Answer 3

I also agree that the JTextArea/JTextField approach is the common and simpler approach.

However if you want to complicate your life a little then you can check out Protected Text Component which will do most of the logic for you.

The current implemtation of the ProtectedDocument only allows you to add protection to the Document, not remove it so the first thing you will need to do is add a method to "Clear" all the protect pieces of text. This is easy enough, you just clear the entries in the Map used by the class.

Next you will need to replace the default "Enter" Action used by the JTextPane. You do this by playing with the Key Bindings of the text area. See Key Bindings for some basic information. In your custom Action you would first need to invoke the newly created "clear(...)" method. Then you would add you text to the text area. Finally you would protect all the text but the last "x" number of characters.