Talkback produced a null pointer exception when being enabled and disabled
repeatedly due to a race condition between the onDestroy() of the service,
and the use of the service itself. The error occurs when one Talkback
thread initiates the destruction of the service (call to onDestroy()) when
it invokes shutdown() on its TextToSpeech instance (the client of the
service). At the same time, Talkback tries to say that "Accessibility" is
unchecked from another thread. During onDestroy(), the reference to the
TTS engine (sNativeSynth) is reset to null, which is used in the service
in speakInternalOnly(), and setLanguage().
The fix consists in the addition of a static variable that signals that
the service has entered onDestroy(). Once this flag is set, all method
invocations on sNativeSynth will be dismissed. Note that access to the
native resources used by sNativeSynth are synchronized at the native
layer, therefore preventing sNativeSynth.shutdown() to interfere with
a sNativeSynth.speak() call already underway.
Removed the TTS_ prefix in the TextToSpeech class to follow the standard naming convention.
Moved the TTS-related intents from the Intent class to TextToSpeech and TextToSpeech.Engine.
Renamed the TextToSpeech.Engine constants that are used as extras for the
ACTION_TTS_CHECK_TTS_DATA intent to prefix them with EXTRA_.
Cleaned up the other TextToSpeech.Engine constant to remove superfluous mentions of
"TTS" in the name.
Merge commit '79858fe2f5b088ad93e461ea94e544bfce3c2e09'
* commit '79858fe2f5b088ad93e461ea94e544bfce3c2e09':
Fixing bug #2008185 - problem with the TTS dropping
utterances under heavy load was caused by the speech
queue being locked. Switched to using a timeout with
tryLock so that the TTS service does not give up
immediately.
Initial commit for review.
Integrated comments after patch set 1 review.
Fixed lockup in AudioFlinger::ThreadBase::exit()
Fixed lockup when playing tone with AudioPlocyService startTone()
so it can be recreated when the service is initialized.
In the interface with the native synthesizer library, close the lib
in the finalizer, delete the global ref to the SynthProxy java object.
for all current TextToSpeech instances by only caching the language
value so it is used with each subsequent utterance for this instance.
Synchronize calls to the engine around a global mutex since the engine
isn't thread-safe, except for the stop() call which is meant to interrupt
the synthesis loop.
* changes:
Fixing a bug in how stop works - keep stop from always stopping the currently speaking item if that item does not belong to the app that is trying to do the stop.
the currently speaking item if that item does not belong to the
app that is trying to do the stop.
Also adds back the functionality of globally stopping speech that
was lost when utterance IDs were added (needed by screen reader).
* changes:
In the native layer for the TTS service, delete the data allocated for the callback after the signal for the end of the synthesis has been received.
