Android APIs
public abstract class

TextToSpeechService

extends Service
java.lang.Object
   ↳ android.content.Context
     ↳ android.content.ContextWrapper
       ↳ android.app.Service
         ↳ android.speech.tts.TextToSpeechService

Class Overview

Abstract base class for TTS engine implementations. The following methods need to be implemented.

The first three deal primarily with language management, and are used to query the engine for it's support for a given language and indicate to it that requests in a given language are imminent. onSynthesizeText(SynthesisRequest, SynthesisCallback) is central to the engine implementation. The implementation should synthesize text as per the request parameters and return synthesized data via the supplied callback. This class and its helpers will then consume that data, which might mean queueing it for playback or writing it to a file or similar. All calls to this method will be on a single thread, which will be different from the main thread of the service. Synthesis must be synchronous which means the engine must NOT hold on the callback or call any methods on it after the method returns onStop() tells the engine that it should stop all ongoing synthesis, if any. Any pending data from the current synthesis will be discarded.

Summary

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Inherited Constants
From class android.app.Service
From class android.content.Context
From interface android.content.ComponentCallbacks2
Public Constructors
TextToSpeechService()
Public Methods
IBinder onBind(Intent intent)
Return the communication channel to the service.
void onCreate()
Called by the system when the service is first created.
void onDestroy()
Called by the system to notify a Service that it is no longer used and is being removed.
Protected Methods
Set<String> onGetFeaturesForLanguage(String lang, String country, String variant)
Queries the service for a set of features supported for a given language.
abstract String[] onGetLanguage()
Returns the language, country and variant currently being used by the TTS engine.
abstract int onIsLanguageAvailable(String lang, String country, String variant)
Checks whether the engine supports a given language.
abstract int onLoadLanguage(String lang, String country, String variant)
Notifies the engine that it should load a speech synthesis language.
abstract void onStop()
Notifies the service that it should stop any in-progress speech synthesis.
abstract void onSynthesizeText(SynthesisRequest request, SynthesisCallback callback)
Tells the service to synthesize speech from the given text.
[Expand]
Inherited Methods
From class android.app.Service
From class android.content.ContextWrapper
From class android.content.Context
From class java.lang.Object
From interface android.content.ComponentCallbacks
From interface android.content.ComponentCallbacks2

Public Constructors

public TextToSpeechService ()

Added in API level 14

Public Methods

public IBinder onBind (Intent intent)

Added in API level 14

Return the communication channel to the service. May return null if clients can not bind to the service. The returned IBinder is usually for a complex interface that has been described using aidl.

Note that unlike other application components, calls on to the IBinder interface returned here may not happen on the main thread of the process. More information about the main thread can be found in Processes and Threads.

Parameters
intent The Intent that was used to bind to this service, as given to Context.bindService. Note that any extras that were included with the Intent at that point will not be seen here.
Returns
  • Return an IBinder through which clients can call on to the service.

public void onCreate ()

Added in API level 14

Called by the system when the service is first created. Do not call this method directly.

public void onDestroy ()

Added in API level 14

Called by the system to notify a Service that it is no longer used and is being removed. The service should clean up any resources it holds (threads, registered receivers, etc) at this point. Upon return, there will be no more calls in to this Service object and it is effectively dead. Do not call this method directly.

Protected Methods

protected Set<String> onGetFeaturesForLanguage (String lang, String country, String variant)

Added in API level 15

Queries the service for a set of features supported for a given language.

Parameters
lang ISO-3 language code.
country ISO-3 country code. May be empty or null.
variant Language variant. May be empty or null.
Returns
  • A list of features supported for the given language.

protected abstract String[] onGetLanguage ()

Added in API level 14

Returns the language, country and variant currently being used by the TTS engine. Can be called on multiple threads.

Returns
  • A 3-element array, containing language (ISO 3-letter code), country (ISO 3-letter code) and variant used by the engine. The country and variant may be "". If country is empty, then variant must be empty too.

protected abstract int onIsLanguageAvailable (String lang, String country, String variant)

Added in API level 14

Checks whether the engine supports a given language. Can be called on multiple threads. Its return values HAVE to be consistent with onLoadLanguage.

Parameters
lang ISO-3 language code.
country ISO-3 country code. May be empty or null.
variant Language variant. May be empty or null.
Returns

protected abstract int onLoadLanguage (String lang, String country, String variant)

Added in API level 14

Notifies the engine that it should load a speech synthesis language. There is no guarantee that this method is always called before the language is used for synthesis. It is merely a hint to the engine that it will probably get some synthesis requests for this language at some point in the future. Can be called on multiple threads. In <= Android 4.2 (<= API 17) can be called on main and service binder threads. In > Android 4.2 (> API 17) can be called on main and synthesis threads.

Parameters
lang ISO-3 language code.
country ISO-3 country code. May be empty or null.
variant Language variant. May be empty or null.
Returns

protected abstract void onStop ()

Added in API level 14

Notifies the service that it should stop any in-progress speech synthesis. This method can be called even if no speech synthesis is currently in progress. Can be called on multiple threads, but not on the synthesis thread.

protected abstract void onSynthesizeText (SynthesisRequest request, SynthesisCallback callback)

Added in API level 14

Tells the service to synthesize speech from the given text. This method should block until the synthesis is finished. Called on the synthesis thread.

Parameters
request The synthesis request.
callback The callback the the engine must use to make data available for playback or for writing to a file.