Xamarin.Forms 2017 TTS无报错但无法发声问题求助

Hey there, let’s work through why your text-to-speech isn’t producing sound even though your code runs without errors. I’ve tackled similar quirks with older Xamarin.Forms versions, so here’s a breakdown of fixes for both approaches you tried, plus some universal checks:

1. For the Official Dependency Service Approach #

• Verify Android Permissions: Double-check your AndroidManifest.xml includes the internet permission:

  <uses-permission android:name="android.permission.INTERNET"/>
  

  Many default TTS engines require this to fetch voice data, even for offline voices in some cases.
• Validate Android Implementation:
  • Ensure your TextToSpeechImplementation inherits from Java.Lang.Object and your shared interface, and has the correct dependency registration:

    [assembly: Dependency(typeof(TextToSpeechImplementation))]
    namespace YourApp.Droid
    {
        public class TextToSpeechImplementation : Java.Lang.Object, ITextToSpeech
        {
            // ... rest of your code
        }
    }
    

  • Make sure the OnInit method returns OperationResult.Success and you’re waiting for the TTS engine to initialize before calling Speak. Add a flag like _isInitialized to avoid speaking before the engine is ready.
• iOS Simulator/Device Checks:
  • Confirm your iOS simulator/device isn’t muted, and volume is turned up. It’s an easy oversight!
  • Ensure your iOS implementation correctly uses AVSpeechSynthesizer—double-check that you’re creating an instance and calling SpeakUtterance with a valid AVSpeechUtterance object.

2. For the Plugins for Xamarin and Windows Approach #

• Match Plugin Version to Xamarin.Forms 2017: Newer plugin versions often drop support for older Xamarin.Forms releases. Look for a stable plugin version compatible with 2017-era Xamarin.Forms (avoid the latest versions here).
• Initialize Early: Don’t wait until the button click to initialize the plugin. Call CrossTextToSpeech.Current.Init() in your MainActivity (Android) OnCreate method or AppDelegate (iOS) FinishedLaunching method to ensure the engine is ready when you need it.
• Check Platform-Specific Quirks:
  • On Android, the same internet permission rule applies as above.
  • On iOS, some older plugin versions might require you to add a usage description to Info.plist—though TTS usually doesn’t need one, it’s worth verifying if the plugin docs mention it for your version.

Universal Troubleshooting Steps #

• Test with Simple Text: Start with a short, plain phrase like "Hello World" to rule out issues with special characters or long text blocks.
• Catch Hidden Exceptions: Wrap your TTS call in a try-catch block to capture any silent failures (like unmanaged Java/iOS exceptions):

  try
  {
      // For plugin approach
      await CrossTextToSpeech.Current.SpeakAsync("Hello World");
      // For dependency service approach
      await DependencyService.Get<ITextToSpeech>().SpeakAsync("Hello World");
  }
  catch (Exception ex)
  {
      System.Diagnostics.Debug.WriteLine($"TTS Failure: {ex.Message}\n{ex.StackTrace}");
      // Optionally display this error to the user for debugging
  }
  

• Check TTS Engine Availability (Android): Go to your device’s Settings > Language & Input > Text-to-Speech Output and confirm there’s an enabled TTS engine (like Google Text-to-Speech). If none are installed, download one from the Play Store.

Work through these steps one by one—most silent TTS issues in older Xamarin versions boil down to missing permissions, uninitialized engines, or overlooked device settings.

内容的提问来源于stack exchange，提问作者Mr Johnston