Android 语音识别将数据传回 Xamarin Forms

Question

我现在真的卡住了，我对 Xamarin 很陌生。 我使用 Xamarin Forms 开发具有语音识别功能的应用程序。

我只创建了一个带有按钮和输入框的简单 UI。

工作：

• 按下按钮并显示带有语音识别的弹出窗口
• 将口语读入 var

不工作：

• 将数据传回 Xamarin Forms UI（条目）

StartPage.xaml.cs：

    private void BtnRecord_OnClicked(object sender, EventArgs e)
    {
        WaitForSpeechToText();
    } 

    private async void WaitForSpeechToText()
    {
        EntrySpeech.Text = await DependencyService.Get<Listener.ISpeechToText>().SpeechToTextAsync();
    }

ISpeechToText.cs：

public interface ISpeechToText
{
    Task<string> SpeechToTextAsync();
}

调用本机代码。

SpeechToText_Android.cs：

    public class SpeechToText_Android : ISpeechToText
    {
    private const int VOICE = 10;

    public SpeechToText_Android() { }

    public Task<string> SpeechToTextAsync()
    {
        var tcs = new TaskCompletionSource<string>();

        try
        {
            var voiceIntent = new Intent(RecognizerIntent.ActionRecognizeSpeech);
            voiceIntent.PutExtra(RecognizerIntent.ExtraLanguageModel, RecognizerIntent.LanguageModelFreeForm);
            voiceIntent.PutExtra(RecognizerIntent.ExtraPrompt, "Sprechen Sie jetzt");
            voiceIntent.PutExtra(RecognizerIntent.ExtraSpeechInputCompleteSilenceLengthMillis, 1500);
            voiceIntent.PutExtra(RecognizerIntent.ExtraSpeechInputPossiblyCompleteSilenceLengthMillis, 1500);
            voiceIntent.PutExtra(RecognizerIntent.ExtraSpeechInputMinimumLengthMillis, 15000);
            voiceIntent.PutExtra(RecognizerIntent.ExtraMaxResults, 1);
            voiceIntent.PutExtra(RecognizerIntent.ExtraLanguage, Java.Util.Locale.Default);

            try
            {
                ((Activity)Forms.Context).StartActivityForResult(voiceIntent, VOICE);

            }
            catch (ActivityNotFoundException a)
            {
                tcs.SetResult("Device doesn't support speech to text");
            }
        }
        catch (Exception ex)
        {

            tcs.SetException(ex);
        }

        return tcs.Task;
    }
}

MainActivity.cs：

    protected override void OnActivityResult(int requestCode, Result resultVal, Intent data)
    {  
        if (requestCode == VOICE)
        {
            if (resultVal == Result.Ok)
            {
                var matches = data.GetStringArrayListExtra(RecognizerIntent.ExtraResults);
                if (matches.Count != 0)
                {
                    string textInput = matches[0].ToString();
                    if (textInput.Length > 500)
                        textInput = textInput.Substring(0, 500);
                }
                // RETURN 
            }
        }
        base.OnActivityResult(requestCode, resultVal, data);
    }

首先我认为我可以通过

return tcs.Task;

回到 ui，但后来我注意到这个返回发生在 语音识别的弹出窗口已完成渲染。这一刻，一句话也没说。

口语在 OnActivityResult 函数中的字符串“textInput”中， 但是我怎样才能将此字符串传递回 Xamarin.Forms UI？

谢谢大家！

Answer 1

我会使用 AutoResetEvent 暂停返回，直到调用 OnActivityResult，直到用户记录某些内容、取消或您在 AutoResetEvent 中超时他们的操作。

从您的 SpeechToTextAsync 方法返回一个 Task<string>：

public interface ISpeechToText
{
    Task<string> SpeechToTextAsync();
}

将AutoResetEvent 添加到暂停执行：

注意：包裹AutoResetEvent.WaitOne以防止挂起应用程序循环

public class SpeechToText_Android : Listener.ISpeechToText
{
    public static AutoResetEvent autoEvent = new AutoResetEvent(false);
    public static string SpeechText;
    const int VOICE = 10;

    public async Task<string> SpeechToTextAsync()
    {
        var voiceIntent = new Intent(RecognizerIntent.ActionRecognizeSpeech);
        voiceIntent.PutExtra(RecognizerIntent.ExtraLanguageModel, RecognizerIntent.LanguageModelFreeForm);
        voiceIntent.PutExtra(RecognizerIntent.ExtraPrompt, "Sprechen Sie jetzt");
        voiceIntent.PutExtra(RecognizerIntent.ExtraSpeechInputCompleteSilenceLengthMillis, 1500);
        voiceIntent.PutExtra(RecognizerIntent.ExtraSpeechInputPossiblyCompleteSilenceLengthMillis, 1500);
        voiceIntent.PutExtra(RecognizerIntent.ExtraSpeechInputMinimumLengthMillis, 15000);
        voiceIntent.PutExtra(RecognizerIntent.ExtraMaxResults, 1);
        voiceIntent.PutExtra(RecognizerIntent.ExtraLanguage, Java.Util.Locale.Default);

        SpeechText = "";
        autoEvent.Reset();
        ((Activity)Forms.Context).StartActivityForResult(voiceIntent, VOICE);
        await Task.Run(() => { autoEvent.WaitOne(new TimeSpan(0, 2, 0)); });
        return SpeechText;
    }
}

MainActivity OnActivityResult：

    const int VOICE = 10;
    protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
    {
        base.OnActivityResult(requestCode, resultCode, data);
        if (requestCode == VOICE)
        {
            if (resultCode == Result.Ok)
            {
                var matches = data.GetStringArrayListExtra(RecognizerIntent.ExtraResults);
                if (matches.Count != 0)
                {
                    var textInput = matches[0];
                    if (textInput.Length > 500)
                        textInput = textInput.Substring(0, 500);
                    SpeechToText_Android.SpeechText = textInput;
                }
            }
            SpeechToText_Android.autoEvent.Set();
        }
    }

注意：这是使用几个静态变量来简化此示例的实现...有些开发人员会说这是代码异味，我半同意，但您不能拥有多个 Google语音识别器一次运行....

Hello World 示例：

public class App : Application
{
    public App()
    {
        var speechTextLabel = new Label
        {
            HorizontalTextAlignment = TextAlignment.Center,
            Text = "Waiting for text"
        };

        var speechButton = new Button();
        speechButton.Text = "Fetch Speech To Text Results";
        speechButton.Clicked += async (object sender, EventArgs e) =>
        {
            var speechText = await WaitForSpeechToText();
            speechTextLabel.Text = string.IsNullOrEmpty(speechText) ? "Nothing Recorded" : speechText;
        };

        var content = new ContentPage
        {
            Title = "Speech",
            Content = new StackLayout
            {
                VerticalOptions = LayoutOptions.Center,
                Children = {
                    new Label {
                        HorizontalTextAlignment = TextAlignment.Center,
                        Text = "Welcome to Xamarin Forms!"
                    },
                    speechButton,
                    speechTextLabel
                }
            }
        };
        MainPage = new NavigationPage(content);
    }

    async Task<string> WaitForSpeechToText()
    {
        return await DependencyService.Get<Listener.ISpeechToText>().SpeechToTextAsync();
    }
}