Java addWindowListener语法错误

Question

I have been searching google and this website all morning, but I don't really know what I am doing wrong. I have created a class (Wallboard) and I am trying to call it, but when compiling it keeps giving errors on the "addWindowListener".

This is the error I get:

error: constructor Wallboard in class Wallboard cannot be applied to given types;
addWindowListener(new Wallboard(this));
                  ^
  required: no arguments
  found: Wallboard
  reason: actual and formal argument lists differ in length

And this is the code:

public class Wallboard
extends JFrame
implements Runnable
{
JLabel WbText;
Thread t = null;
String[] textLine = new String[4];

public Wallboard()
{
setUndecorated(true);
setExtendedState(6);
getContentPane().setBackground(Color.BLACK);
getContentPane().setCursor(Toolkit.getDefaultToolkit().createCustomCursor(new BufferedImage(16, 16, 2), new Point(0, 0), null));

setVisible(true);
this.WbText = new JLabel("0123456789012345", 0);
this.WbText.setFont(new Font("Monospaced", 1, getWidth() * 18 / 160));
this.WbText.setHorizontalTextPosition(0);
this.WbText.setVerticalTextPosition(0);
add(this.WbText);
addWindowListener(new Wallboard(this));

this.t = new Thread(this);
this.t.start();
}

Could anyone help me out? What am I doing wrong?

Many thanks for your input.

Answer 1

Seems like your constructor has no arguments:

public Wallboard() {
    setUndecorated(true);
    setExtendedState(6);
    ...

And you then try to call it using this asn argument:

addWindowListener(new Wallboard(this));

There should be something else that implements WindowListener instead of new Wallboard(this) inside addWindowsListener() . Try this out instead:

addWindowListener(new WindowListener() {});

Answer 2

You are creating a new instance of Wallboard in the constructor of Wallboard. Even if it would compile, it will cause an infinite loop. Instead, call addWindowListener with the current object. I think what you want to do is this:

public class Wallboard
extends JFrame
implements Runnable, WindowListener
{

     public Wallboard() 
     {
          ...
          addWindowListener(this);
          ...
     }

     public void windowOpened(WindowEvent e) {
     }
     ...
}

You have to implement the windowOpened and all the other methods in the WindowListener interface as well.