How to stop/cut-off xamarin essentials text-to-speech on iOS to start new speech

Question

Having trouble stopping xamarin essentials text-to-speech in order to start a new text to speech "SpeakAsync" call w/ Xamarin.Forms.

Using this application as a simulated operator for a "practice phone call", I would like to cut off the operator saying "hello this is...." when the user hangs up the call, and use speak async to start saying "This call has ended" immediately after cutting off the previous text to speech

await TextToSpeech.SpeakAsync("Hello this is the operator, thank you for calling, how can I help you?"
    , SpeechTokenSource.Token);

This currently works as expected on android

public void CancelSpeech()
{
    if (SpeechTokenSource?.IsCancellationRequested ?? true)
    return;

    SpeechTokenSource.Cancel();
}

Trying to use cancellation token as listed in the documentation (https://learn.microsoft.com/en-us/xamarin/essentials/text-to-speech) however I cannot get the current "SpeakAsync" speech to stop playing immediately on iOS, or the next speakasync command to start speaking the text on iOS once the initial text-to-speech is cancelled.

   CancelSpeech();

   IsCallActive = false;
   DialedText = null;

   //Reset speech cancellation token
   SpeechTokenSource = new CancellationTokenSource();

   await TextToSpeech.SpeakAsync("This call has ended. Goodbye."
   , SpeechTokenSource.Token);

Error logged in iOS output: "[AXTTSCommon] _BeginSpeaking: couldn't begin playback"

Is there something I am missing? how can I cancel the current text-to-speech that is playing and start the next speech immediately after?

Edit:

This needs to be done on a single button tap (both canceling current speech and starting the "This call has ended" speech)

Answer 1

I am unable to reproduce your problem.

The below code works on both iOS and Android using Xamarin.Essentials v1.3.0 and Xamarin.Forms v4.2.0.709249.

When the speakButton is tapped, text is spoken and when the cancelButton is tapped while the text is being spoken, the speaking stops.

There is one difference when cancelling SpeakAsync on iOS vs Android:

• On iOS, the current word being spoken is finished and then the speaking stops
• On Android, the current word being spoken is cut off and the speaking stops

Sample Code

The complete sample app can be found here: https://github.com/brminnick/CancelTextToSpeechSample/tree/master

using System;
using System.Threading;
using Xamarin.Forms;

namespace CancelTextToSpeechSample
{
    public class App : Application
    {
        public App()
        {
            MainPage = new CancelSpeakPage();
        }

        class CancelSpeakPage : ContentPage
        {
            const string _spokenText = "Oh, supercalifragilisticexpialidocious! Even though the sound of it, Is something quite atrocious, If you say it loud enough, You'll always sound precocious, Supercalifragilisticexpialidocious!";

            CancellationTokenSource _speakButtonCancellationTokenSource;

            public CancelSpeakPage()
            {
                var speakButton = new Button { Text = "Sing" };
                speakButton.Clicked += HandleSpeakButtonClicked;

                var cancelButton = new Button { Text = "Cancel Song" };
                cancelButton.Clicked += HandleCancelButtonClicked;

                Content = new StackLayout
                {
                    VerticalOptions = LayoutOptions.Center,
                    HorizontalOptions = LayoutOptions.Center,

                    Children =
                    {
                        speakButton,
                        cancelButton
                    }
                };
            }

            void HandleCancelButtonClicked(object sender, EventArgs e)
            {
                _speakButtonCancellationTokenSource?.Cancel();
            }

            async void HandleSpeakButtonClicked(object sender, EventArgs e)
            {
                if (_speakButtonCancellationTokenSource?.IsCancellationRequested is false)
                    _speakButtonCancellationTokenSource.Cancel();

                _speakButtonCancellationTokenSource = new CancellationTokenSource();
                await Xamarin.Essentials.TextToSpeech.SpeakAsync(_spokenText, _speakButtonCancellationTokenSource.Token);
            }
        }
    }
}