Why am I getting this error as I try from withing the anonymous class?

Question

I get an error that says :

no suitable method found for showMessageDialog(<anonymous Runnable>,String,String,int) as I try to use the JOptionPane.show... method. Why is that ?

private void connectivityChecker() {

    Runnable r = new Runnable() {
        @Override
        public void run() {
            try {
                Thread.sleep(3000);
            }catch(Exception exc) {
                System.out.println("Thread Interrupted !");
            }

            boolean isConnected = Internet.isConnected();
            if(!isConnected) {
                JOptionPane.showMessageDialog(this, "You have lost connectivity to the server", "Connection Error", JOptionPane.ERROR_MESSAGE);
            }
        }
    };
    new Thread(r,"Connectivity Checker - UserGUI").start();
}

Answer 1

When you are referring to this it points to inner class, not the outer class which you are thinking.

Try to tell that point to outer class, not the anonymous inner class.

 JOptionPane.showMessageDialog(OuterClassName.this, <--------
              "You have lost connectivity to the server", 
                  "Connection Error", JOptionPane.ERROR_MESSAGE);

Answer 2

when you refer this within the anonymous class, it refers to the anonymous class instance itself. Since you are creating a Runnable anonymous instance, this refers to that Runnable instance.

JOptionPane.showMessageDialog(..) does't accept Runnable, so you might want to do something like this

private void connectivityChecker() {

    Runnable r = new Runnable() {
        @Override
        public void run() {
            try {
                Thread.sleep(3000);
            }catch(Exception exc) {
                System.out.println("Thread Interrupted !");
            }

            boolean isConnected = Internet.isConnected();
            if(!isConnected) {
                showErrorMessage("You have lost connectivity to the server", "Connection Error" );
            }
        }
    };
    new Thread(r,"Connectivity Checker - UserGUI").start();
}

private void showErrorMessage(String message, String header) {
     JOptionPane.showMessageDialog(this, message, header, JOptionPane.ERROR_MESSAGE);
}

In above, since this is called from showMessage(), it refers to the instance of the main class in which showMessage() is defined

Answer 3

The code snippet did not even compile for me and throwing an error on JOptionPane.showMessageDialog(this ...

Because this should be extending Component. Anyways I tried extended my outer class with Component and the code below worked for me without any issues.

    if (!isConnected) {
      JOptionPane.showMessageDialog(ThisAmbiguity.this, "You have lost connectivity to the server", "Connection Error", JOptionPane.ERROR_MESSAGE);
    }

ThisAmbiguity is my outer class. So, when you are referring to this in anonymous inner class so its pointing inner class.