这是Android的书，我有一定的状态，使用 TextToSpeech.playEarcon（）是preferable播放音频文件（使用MediaPlayer的），因为：

An Android book I have states that using TextToSpeech.playEarcon() is preferable to playing audio files (using MediaPlayer) because:

而不必确定时机来播放音频   线索并依靠回调来获得合适的时机，我们可以改为   排队我们earcons我们发送给TTS引擎的文字之中。然后，我们   知道我们earcons将会在适当的时间播放，并且我们   可以使用相同的途径得到我们的声音给用户，包括    onUtteranceCompleted（）的回调让我们知道我们在哪里。

Instead of having to determine the opportune moment to play an audible cue and relying on callbacks to get the timing right, we can instead queue up our earcons among the text we send to the TTS engine. We then know that our earcons will be played at the appropriate time, and we can use the same pathway to get our sounds to the user, including the onUtteranceCompleted() callbacks to let us know where we are.

但我的简短的实验，这表明该不的情况：

But my short and simple experiment with this shows this isn't the case:

String utteranceId = String.valueOf(utteranceNum++);
params.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, utteranceId);
params.put(TextToSpeech.Engine.KEY_PARAM_STREAM, String.valueOf(AudioManager.STREAM_MUSIC));
tts.speak("FIRST part of sentence", TextToSpeech.QUEUE_ADD, params);

utteranceId = String.valueOf(utteranceNum++);
params.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, utteranceId);
params.put(TextToSpeech.Engine.KEY_PARAM_STREAM, String.valueOf(AudioManager.STREAM_MUSIC));
tts.playEarcon("[fancyring]", TextToSpeech.QUEUE_ADD, params);

utteranceId = String.valueOf(utteranceNum++);
params.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, utteranceId);
params.put(TextToSpeech.Engine.KEY_PARAM_STREAM, String.valueOf(AudioManager.STREAM_MUSIC));
tts.speak("SECOND part of sentence", TextToSpeech.QUEUE_ADD, params);

当我检查日志从 onUtteranceCompleted（）我只看到由 tts.speak的utteranceIds（），而不是一个被打了 tts.playEarcon（）。

When I examine the logs from onUtteranceCompleted() I only see the utteranceIds of the ones played by tts.speak(), not the one played by tts.playEarcon().

为什么这种差异？是否有解决方法吗？

Why is this discrepancy? Is there a workaround for this?

PS 在说明明显的风险：这三种话语都发挥了罚款，并在正确的顺序。这仅仅是 onUtteranceCompleted（）未要求某种原因 tts.playEarcon（）。

P.S. At the risk of stating the obvious: All three utterances are played out fine and at the right order. It is only the onUtteranceCompleted() that isn't called for some reason for the tts.playEarcon().

推荐答案

回答自己。有关的令人难以置信的长，非常详细的文档 TextToSpeech.OnUtteranceCompletedListener 读（强调的是我的）：

Answering myself. The incredibly long and very detailed documentation about TextToSpeech.OnUtteranceCompletedListener reads (the emphasis is mine):

调用时，话语一直合成

这是earcon是从未的综合后的结果，所以当然 onUtteranceCompleted（）会的永远的调用它。这是由设计。

An earcon is never a result of synthesization, so of course onUtteranceCompleted() will never be called for it. This is by design.

这会让我们回到一个新的问题：如果要earcons没有优势播放.mp3文件（使用MediaPlayer的），为什么要使用earcons在所有

Which gets us back to a new question: If there is no advantage to earcons over playing .mp3 files (using MediaPlayer), why use earcons at all?