Pass the outer class anon ref to the method in the inner class anon

Question

How to pass an anon ref outer class to a method in an anon inner class in Java?

I have a method that makes an asynchronous call on the server - sendCall(some_args, callback) . The callback is represented by an anonymous class (let its name be OuterAnon ) and contains a method for the case of failure. A message box is created inside this method, and sendCall() is called each time the OK button is clicked. So I need to pass OuterAnon method again.

Here is the code demonstrating what I mean:

 private void sendCall(MyData data, OuterAnon<Boolean> callback){/*...*/} private void myCall(final MyData data) { sendCall(data, new OuterAnon<Boolean>() { public void onFailure(Throwable throwable) { final OuterAnon<Boolean> callback = this; //how to avoid this? MessageBox.show(throwable.getMessage(), new MessageListener() { public void process(MessageBox.OnClick action) { if (action == MessageBox.OnClick.OK) { sendCall(new MyData("resend?"), callback); } } }); } } }); } 

As you noticed, I take the link for the callback here:

 final OuterAnon<Boolean> callback = this; 

and use it here:

 sendCall(new MyData("resend?"), callback); 

But I want to avoid creating a ref and do a callback, for example:

 sendCall(new MyData("resend?"), this); //at the moment we point to MessageListener instead of OuterAnon. 

Is there any way to do this in Java?

Answer 1

It’s hard for us to fix, since you were only showing incomplete code with classes that are not supplied, so I don’t know if this example is syntactically correct. At the same time, refactoring like this can satisfy your needs:

  private void myCall(final MyData data) { sendCall(data, new OuterAnon<Boolean>() { public void onFailure(Throwable throwable) { showErrorMessage(throwable); } }); } private void showErrorMessage(Throwable throwable) { MessageBox.show(throwable.getMessage(), new MessageListener() { public void process(MessageBox.OnClick action) { if (action == MessageBox.OnClick.OK) { sendCall(new MyData("resend?")); } } }); } private void sendCall(MyData data) { sendCall(data, this); } 

In general, I find it usually a good idea to abstract the code from the internal anon classes and into your own method on the enclosing class. It can now be tested, reused and read on, IMO.

Answer 2

If you really need to specify onFailure inside the inner class, as you showed the code, and if you need to use this specific link for callback , and you need to encode this path ...

Let me answer the question: no.

In my attempts, I have achieved three ways to access the anon-inner-smallest instance inside the anon-inner-most instance, but I think no one meets the expected.

In this case, anon-inner-most has no reference to anon-inner-less: as you said, this now points to anon-inner-less.

In addition, I tried to search the java specification , but could not find the exact answer to the question - if someone finds the answer there, please contribute.

My attempt:

 import java.util.ArrayList; import java.util.LinkedList; public abstract class AnonTest { public static void main(String[] args) { new ArrayList<Object>() { private static final long serialVersionUID = -5986194903357006553L; { // initialize inner anon class add("1"); } // Way 1 private Object thisReference1 = this; // Way 2 private Object getThisReference2() { return this; } @Override public boolean equals(Object obj) { // Way 3 final Object thisReference3 = this; new LinkedList<Object>() { private static final long serialVersionUID = 900418265794508265L; { // initialize inner inner anon class add("2"); } @Override public boolean equals(Object innerObj) { // achieving the instance System.out.println(thisReference1); System.out.println(getThisReference2()); System.out.println(thisReference3); System.out.println(this); System.out.println(); // achieving the class System.out.println(thisReference1.getClass()); System.out.println(getThisReference2().getClass()); System.out.println(thisReference3.getClass()); System.out.println(this.getClass()); System.out.println(this.getClass().getEnclosingClass()); return super.equals(innerObj); } }.equals(""); return super.equals(obj); } }.equals(""); } }