Swift 如何使用speechSynthesizer突出显示每个段落并滚动文本视图

我想做的是按下speak按钮，突出显示第一段，然后说出该段，然后将下一段滚动到textView的中心，突出显示该段，然后说出该段。 要做到这一点，我需要添加什么代码

import UIKit
import AVFoundation


class TestViewController: UIViewController, AVSpeechSynthesizerDelegate {

let synthesizer = AVSpeechSynthesizer()


@IBOutlet weak var textViewOutlet: UITextView!


@IBAction func pauseSpeech(_ sender: Any) {
    synthesizer.pauseSpeaking(at: AVSpeechBoundary.word)
}

@IBAction func stopSpeech(_ sender: Any) {
    synthesizer.stopSpeaking(at: .word)
}

@IBAction func cancelButton(_ sender: Any) {
    synthesizer.continueSpeaking()
}

@IBAction func speak(_ sender: AnyObject) {
    let string = textViewOutlet.text!
    let utterance = AVSpeechUtterance(string: string)
        utterance.voice = AVSpeechSynthesisVoice(language: "en-GB")
        synthesizer.speak(utterance)
}


override func viewDidLoad() {
    super.viewDidLoad()
        synthesizer.delegate = self
        textViewOutlet.font = .systemFont(ofSize: 20)
}

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, willSpeakRangeOfSpeechString characterRange: NSRange, utterance: AVSpeechUtterance) {
    let mutableAttributedString = NSMutableAttributedString(string: utterance.speechString)
        mutableAttributedString.addAttribute(NSAttributedStringKey.foregroundColor, value: UIColor.blue, range:  NSMakeRange(0, (utterance.speechString as NSString).length))
        mutableAttributedString.addAttribute(.foregroundColor, value: UIColor.red, range: characterRange)
        textViewOutlet.attributedText = mutableAttributedString
        textViewOutlet.font = .systemFont(ofSize: 20)
}

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {
    textViewOutlet.attributedText = NSAttributedString(string: utterance.speechString)
    textViewOutlet.font = .systemFont(ofSize: 20)
}

}

大概是这样的：

定义属性

   let currentParagraphIndex = 0
   let paragraphs = [Range<String.Index>]()

另见

所以你开始讲第一段，而不仅仅是文本

然后，当段落结束时，在“学员”中开始讲下一段：

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {
    currentParagraphIndex = currentParagraphIndex + 1
    if (currentParagraphIndex < paragraphs.count) {
       let utterance = AVSpeechUtterance(text.substringWithRange(paragraphs[currentParagraphIndex]))
       highlightParagraph(currentParagraphIndex)
       utterance.voice = AVSpeechSynthesisVoice(language: "en-GB")
       synthesizer.speak(utterance)
     }
}

func speechsynthesis（u合成器：avspeechsynthesis，didfish发音：avspeechoutance）{
currentParagraphIndex=currentParagraphIndex+1
if（当前段落索引<段落计数）{
let outrance=avspeechoutrance（text.substringWithRange（段落[currentParagraphIndex]））
高亮段落（当前段落索引）
outrance.voice=AVSpeechSynthesisVoice（语言：“en-GB”）
合成器。说话（说话）
}
}

可能的副本您必须使用AVSpeechSynthesizerDelegateI调用viewDidLoad中的代理。如何通过代理和滚动来逐段检测。我不知道如何用这个答案来解决问题，所以我编辑了我的问题。谢谢你的指导，我已经了解了更多。

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {
    currentParagraphIndex = currentParagraphIndex + 1
    if (currentParagraphIndex < paragraphs.count) {
       let utterance = AVSpeechUtterance(text.substringWithRange(paragraphs[currentParagraphIndex]))
       highlightParagraph(currentParagraphIndex)
       utterance.voice = AVSpeechSynthesisVoice(language: "en-GB")
       synthesizer.speak(utterance)
     }
}