Question

my AsyncTask doInBackground have multiple nested condition which return String to onPostExectue method , which make code very complex is there any alternative way to handle this problem

Now my code look like this

protected String doInBackground(Void... params){
    if (position == 0){ 
         return "Set1" 
    }
    else if(Position >something) { 
         return set 2 
    } .........and so on 
}

@Override
protected void onPostExecute(String result) {
    if (result.equals("set1")){
       // do some taskk
    }
    elseif(result.equal("Set2")){
        // do other task
    }
    else if(){
       // sooo onnnnnn
     }
} 

thanks in advance for your help

Answer 1

One can try to apply Strategy pattern here. You can create an abstract class, say Action, with an abstract function perform(). Then you can create concrete subclasses of Action for every action which can be performed in onPostExecute. So you have classes say ActionForSet1, ActinForSet2 etc with concrete implementations of perform(). Then Action should have a static method String Action createfromString(String set) which will be essentially the same if/else or break but much more maintainable. It will return corresponding Action subclasses for every string. You can use Map instead of if/else in there, easier to add/remove elements then. Then after you have your Action object returned by Action.createFromString you call its perform()

onPostExecute(String result) {
   Action a = Action.actionForResult(result);
   a.perform();
}

abstract class Action {
  abstract void perform();

  static Action actionForResult(String result) {
      if(result.equals("res1") {
          return new ActionForRes1();
      } else if(result.equals("res2") {
          return new ActionForRes2();
      } else throw new IllegalArgumentException("No action for result " + result);
   }
}

class ActionForResult1 extends Action {
  @Override
  void perform() { Log.i("ACTION", "Here's action for result 1"); }
}

class ActionForResult2 extends Action {
  @Override
  void perform() { Log.i("ACTION", "Here's action for result 2"); }
}