CODEWITHSUNDEEP
javauser-interfaceanonymous-class
ldam
ldam

Reputation: 4585

How do I best return a value from an anonymous class in a method?

If I have a method that needs to return something, and it needs to display something on the UI to do that (for example to ask the user a question), I use java.awt.EventQueue.invokeLater(new Runnable() {...}); to run it on the UI thread (Android does something similar using runOnUiThread()). How do I return something from that Runnable? For example:

public String askQuestion()
{
    java.awt.EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            String response = JOptionPane.showInputDialog(null, "What is 2+2?");
            //how do I return this response object to the method?
        }
    });
}

I can't use a final local variable because the compile won't allow me to assign to it. I can use a class variable and access it using Class.this.<variable> but is that the best/only way to accomplish this?

Edit: I need to return things other than String too, this was just an example.

Upvotes: 2

Views: 2308

Answers (1)

Vishal K
Vishal K

Reputation: 13066

You can proceed as follows:

public String askQuestion()throws Exception
   {
    final StringBuilder sBuilder = new StringBuilder();
    java.awt.EventQueue.invokeAndWait(new Runnable() {
        @Override
        public void run() {
            String response = JOptionPane.showInputDialog(null, "What is 2+2?");
            sBuilder.append(response);
        }
    });
   return sBuilder.toString();
}

This could also be solved in following way:

String sResponse;//make sResponse a field of class xyz
public String askQuestion()throws Exception
 {
    java.awt.EventQueue.invokeAndWait(new Runnable() {
        @Override
        public void run() {
            String response = JOptionPane.showInputDialog(null, "What is 2+2?");
            sResponse = response;
        }
    });
   return sResopnse;
}

Upvotes: 3

Related Questions