什么TtsService可以解释playEarcon（）缺少onUtteranceCompleted（）？

A while ago, I discovered that playEarcon() never produces onUtteranceCompleted().

前段时间，我发现playEarcon（）从不生成onUtteranceCompleted（）。

At the time I just interpreted the documentation that said "Called when an utterance has been synthesized" as onUtteranceCompleted() being not applicable for earcons because, an earcon isn't really a result of TTS synthesization.

当时我只是解释说“当话语被合成时调用”的文档，因为onUtteranceCompleted（）不适用于earcons，因为，earcon实际上并不是TTS合成的结果。

But looking again Android's source code, I simply can't find an explanation that would justify my interpretation.

但是再看看Android的源代码，我根本找不到能够证明我解释的解释。

A few facts about my test jig:

关于我的测试夹具的一些事实：

1. onUtteranceCompleted() always arrives for utterance ID preceding the earcon. That utterance is an ordinary TTS utterance, not an earcon.
2. onUtteranceCompleted（）总是到达earcon之前的话语ID。这种话语是普通的TTS话语，而不是一种耳语。
3. The earcon after that does play out (i.e. exactly as intended).
4. 之后的耳塞确实发挥出来（即完全符合预期）。
5. onUtteranceCompleted() for that earcon never shows up. This is very consistent and reproducible behavior.
6. onEtteranceCompleted（）为那个earcon永远不会出现。这是非常一致和可重复的行为。

Delving deep into the TtsService source code, there seem to be only 2 methods that could affect the arrival (or absence) of onUtteranceCompleted():

深入研究TtsService源代码，似乎只有2种方法可以影响onUtteranceCompleted（）的到达（或不存在）：

1. TtsService.processSpeechQueue()
2. TtsService.processSpeechQueue（）
3. TtsService.onCompletion()
4. TtsService.onCompletion（）

If you examine that code, you will see that a 3rd candidate, TtsService.getSoundResource() is ruled out (as being responsible for the lack of onUtteranceComplete for my earcon) because of fact #2 above: The earcon always plays, hence getSoundResource() cannot possibly return null.

如果你检查那个代码，你会看到第三个候选者，TtsService.getSoundResource（）被排除（由于我的earcon缺乏onUtteranceComplete），因为上面的事实＃2：earcon总是在播放，因此getSoundResource（ ）不可能返回null。

Using the same logic, the 1st candidate, TtsService.processSpeechQueue(), can also be ruled out, for the same fact #2: The earcon always plays, hence the following 2 critical statements are always executed:

使用相同的逻辑，第一个候选者TtsService.processSpeechQueue（）也可以被排除，因为相同的事实＃2：earcon总是在播放，因此总是执行以下2个关键语句：

1108   mPlayer.setOnCompletionListener(this);
...
1111   mPlayer.start();

So, we are left with the 2nd candidate only, TtsService.onCompletion(), as a possible explanation for why a playEarcon() never produces onUtteranceCompleted():

所以，我们只剩下第二个候选者TtsService.onCompletion（），作为playEarcon（）永远不会产生onUtteranceCompleted（）的原因的可能解释：

public void onCompletion(MediaPlayer arg0) {
  // mCurrentSpeechItem may become null if it is stopped at the same
  // time it completes.
  SpeechItem currentSpeechItemCopy = mCurrentSpeechItem;
  if (currentSpeechItemCopy != null) {
    String callingApp = currentSpeechItemCopy.mCallingApp;
    ArrayList<String> params = currentSpeechItemCopy.mParams;
    String utteranceId = "";
    if (params != null) {
      for (int i = 0; i < params.size() - 1; i = i + 2) {
        String param = params.get(i);
        if (param.equals(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID)) {
          utteranceId = params.get(i + 1);
        }
      }
    }
    if (utteranceId.length() > 0) {
      dispatchUtteranceCompletedCallback(utteranceId, callingApp);
    }
  }
  processSpeechQueue();
}

In there, there are only 2 conditions that would fail to produce dispatchUtteranceCompletedCallback():

在那里，只有两个条件无法生成dispatchUtteranceCompletedCallback（）：

1. currentSpeechItemCopy == null
2. currentSpeechItemCopy == null
3. utteranceId.length() == 0
4. utteranceId.length（）== 0

But I know for sure that condition #2 can be ruled out because I log all utteranceIds and the earcon's are definitely there.

但我肯定知道条件＃2可以排除，因为我记录所有的话语和耳塞肯定在那里。

Also, examining the entire system log:

另外，检查整个系统日志：

Log.v(SERVICE_TAG, "TTS callback: dispatch started");

The missing onUtteranceCompleted() could be the result of dispatchUtteranceCompletedCallback() not being called, but it could also be the result of mCallbacksMap.get(packageName) returning null.

缺少onUtteranceCompleted（）可能是dispatchUtteranceCompletedCallback（）没有被调用的结果，但它也可能是mCallbacksMap.get（packageName）返回null的结果。

So, we are left again with 2 possibilities, both of which don't make to me much sense:

所以，我们又有两种可能性，这两种可能性对我来说都没有多大意义：

1. By the time an earcon's onCompletion() is called, earcon's mCurrentSpeechItem is null. But why?
2. 当调用earcon的onCompletion（）时，earcon的mCurrentSpeechItem为null。但为什么？
3. mCallbacksMap is empty. What is it and when does it ever get populated?
4. mCallbacksMap为空。什么是它什么时候填充？

Any suggestions or other explanations for solving this mystery?

解决这个谜团的任何建议或其他解释？

1 个解决方案

#1

Check android.speech.tts.TextToSpeech#playEarcon() at line 807. The params argument passed to the text-to-speech service binder is null, which means the service never receives your utterance ID.

检查第807行的android.speech.tts.TextToSpeech＃playEarcon（）。传递给文本转语音服务活页夹的params参数为null，这意味着该服务永远不会收到您的话语ID。

 public int playEarcon(String earcon, int queueMode,
         HashMap<String,String> params) {
     synchronized (mStartLock) {
         ...
         result = mITts.playEarcon(mPackageName, earcon, queueMode, null);
     }
     ...
 }