Java Swing JTextArea镜像

Question

I have made a user interface which has two JTextAreas. I would like one text area to recieve direct input from the user, and I would then essentially like the other one to mirror it exactly. So this means as well as having the exact same characters added to it, it also correctly matches backspaces and return key presses etc. I have attempted to achieve this by emulating backspace and return keypresses using the Robot(int keycode) function, giving it the right keycode 10 being Enter and 8 being Backspace. If it is a regular character then I simply append it to the second JTextArea. This works fine for the characters and return key presses, but pressing Backspace just draws the unknown character rectangle to the mirroring text area.

Ideally I would like to be able to directly pass the events which occur in the input JTextArea to the ouput JTextArea rather than manually working out the appropriate behavior myself.

This is the part of the program which creates the input JTextArea and assigns a keylistener:

inputBox = new JTextArea();
    inputBoxScroller = new JScrollPane();
    inputBoxScroller.setViewportView(inputBox);
    inputBox.addKeyListener(this);

This is the part of the program which recieves the keylisten events and works out what to do based on the keycode of the keys pressed, which I would like to be changed to somehow 'forward' the keylisten event to the output JTextArea, as this would be more ideal.

public void keyTyped(KeyEvent keyevent) {
    String keyPressed = String.valueOf(keyevent.getKeyChar());
    int keyCode = keyevent.getKeyCode();

    if(keyCode == 10) {
        try {
            System.out.println(keyevent.toString());
            autoKeypresser = new Robot();
            outputBox.requestFocus();
            autoKeypresser.keyPress(10);
            inputBox.requestFocus();
        } catch (AWTException e) {
            e.printStackTrace();
        }
    } 

    if(keyCode == 8) {
        try {
            autoKeypresser = new Robot();
            outputBox.requestFocus();
            autoKeypresser.keyPress(8);
            inputBox.requestFocus();
        } catch (AWTException e) {
            e.printStackTrace();
        }
    } else {
        outputBox.append(keyPressed);
    }
}

Answer 1

I would then essentially like the other one to mirror it exactly

All you need to do is share the model:

JTextArea textArea1 = new JTextArea(...);
JTextArea textArea2 = new JTextArea();
textArea2.setDocument( textArea1.getDocument() );

Now whatever you type in either text area will be reflected in both text areas.