Question

I would like to implement system of callbacks which looks like this (pseudo code):

final Listener listener = ListenerCtrl.addListener(new Listener() {
  void onNotify(String response){
    ListenerCtrl.unsetListener(listener);
} }

This code mean that after received message, i want to unscribe from future notifications. I found very attractive have this action inside of callback.

Here is my actual implementation:

final WebServiceMsgListener wml = new WebServiceMsgListener()
{
  public void onMsgNotify(JSONObject response, int ecode)
  {
    Log.v(TAG, "getSetStateProgressBar MSG_MGT_STATICINFO: onMsgNotify ecode" +
       ecode);
    authDelegate.unsetMsgListener(wml);
  }
};

authDelegate.addMsgListener(NAOMsg.MSG_MGT_STATICINFO, wml);

Unfortunately, my current implementation show me eclipse error:“The local variable wml may not have been initialized”

Question: how I can get round this, to finally unscribe inside of callback and dont have this error ?

Answer 1

Change your code to:

authDelegate.unsetMsgListener(this);

this refers to the current object (whose onMsgNotify() is being executed at the time this statement is executed).

Note: Although, the variable wml is available to the new object, it has not yet been initialized at the time of the creation of the object, hence the error. It is initialized right after the object is fully created.