How to end Listen action

I'm struggling to understand how, and if it is possible, to end a listen action on Pepper after it is started. What i want to achieve in my application is the following:

• Pepper asks a question to the user, which in turn can answer either with voice or a touch input on the tablet.
• If the answer is negative, Pepper will have to execute an animation and at the same time reply with a phrase.

This is the part of the code to handle voice input, and it works as expected:

public void onRobotFocusGained(QiContext qiContext) {
         ...

        //Pepper greets the approached user
        animation_future = greeting_animation.async().run();
        //After the animation is finished, wait for human input
        animation_future.andThenConsume(chatting ->{
            listen = ListenBuilder.with(qiContext).withPhraseSet(response).buildAsync();
            listen.andThenConsume(heardPhrase->{
                //Pepper start listening
                result = heardPhrase.run();
                //If the response contains "yes"
                if( (result.getHeardPhrase().getText().toLowerCase()).equals("si")){
                    //User need helps, Pepper start discussing with it
                    helpNeeded_chat.async().run();
                    //Otherwise
                }else if( (result.getHeardPhrase().getText().toLowerCase()).equals("no")){
                    //No help is required, Pepper says goodbye
                    animation_future = goodbye_animation.async().run();
                    //A new user comes by - Restart scenario
                    animation_future.andThenConsume(restart->{
                        Log.i(TAG, "Interaction ended. Restarting.");
                        //Restart by starting this same activity
                        startActivity(new Intent(this, MainActivity.class));
                    });
                }
            });
        });
    }

While this is the part that handles touch inputs (defined in its own method outside onRobotFocusGained):

final Button button_no = findViewById(R.id.button_no);
button_no.setOnClickListener(v->{
    ...
    listen.requestCancellation();
    //Help is refused - Restart scenario
    animation_future = goodbye_animation.async().run();
    animation_future.andThenConsume(restart->{
        Log.i(TAG, "Interaction ended. Restarting.");
        //Restart by starting this same activity
        startActivity(new Intent(this, MainActivity.class));
    });
});

In this case since the Listen action keeps running then the warning Pepper can not speak while is listening is thrown thus preventing correct ending of the task.
What I have found is that the only method that might allow to terminate actions is requestCancellation() but it doesn't seems to work in my case, the boolean method isCancelled() to check whether the action is terminated keeps returning always False.

It is actually possible to stop the Listen action or do I have to entirely change the way in which my code is structured (i.e. use a chatbot from the very beginning)?

When you are calling listen.requestCancellation(), you are in fact cancelling the building of the listen action.
You defined listen with:
listen = ListenBuilder.with(qiContext).withPhraseSet(response).buildAsync();.

Instead, you should cancel the future returned when you run the action: result = heardPhrase.run();.
Calling result.requestCancellation() should do the trick for you.

The thumb rule is that Qi SDK actions are first built then run.