Translate text with ML Kit on Android

You can use ML Kit to translate text between languages. ML Kit can translation between more than 50 languages.

Try it out

• Play around with the sample app to see an example usage of this API.

Before you begin

1. In your project-level build.gradle file, make sure to include Google's Maven repository in both your buildscript and allprojects sections.
2. Add the dependencies for the ML Kit Android libraries to your module's app-level gradle file, which is usually app/build.gradle:

   dependencies{
   // ...
   implementation'com.google.mlkit:translate:17.0.3'
   }

Translate a string of text

To translate a string between two languages:

1. Create a Translator object, configuring it with the source and target languages:

   Kotlin

   // Create an English-German translator:
   valoptions=TranslatorOptions.Builder()
   .setSourceLanguage(TranslateLanguage.ENGLISH)
   .setTargetLanguage(TranslateLanguage.GERMAN)
   .build()
   valenglishGermanTranslator=Translation.getClient(options)

   Java

   // Create an English-German translator:
   TranslatorOptionsoptions=
   newTranslatorOptions.Builder()
   .setSourceLanguage(TranslateLanguage.ENGLISH)
   .setTargetLanguage(TranslateLanguage.GERMAN)
   .build();
   finalTranslatorenglishGermanTranslator=
   Translation.getClient(options);

   If you don't know the language of the input text, you can use the Language Identification API which gives you a language tag. Then convert the tag to a TranslateLanguage using TranslateLanguage.fromLanguageTag().

   Avoid keeping too many language models on the device at once.

2. Make sure the required translation model has been downloaded to the device. Don't call translate() until you know the model is available.

   Kotlin

   varconditions=DownloadConditions.Builder()
   .requireWifi()
   .build()
   englishGermanTranslator.downloadModelIfNeeded(conditions)
   .addOnSuccessListener{
   // Model downloaded successfully. Okay to start translating.
   // (Set a flag, unhide the translation UI, etc.)
   }
   .addOnFailureListener{exception->
   // Model couldn’t be downloaded or other internal error.
   // ...
   }

   Java

   DownloadConditionsconditions=newDownloadConditions.Builder()
   .requireWifi()
   .build();
   englishGermanTranslator.downloadModelIfNeeded(conditions)
   .addOnSuccessListener(
   newOnSuccessListener(){
   @Override
   publicvoidonSuccess(Voidv){
   // Model downloaded successfully. Okay to start translating.
   // (Set a flag, unhide the translation UI, etc.)
   }
   })
   .addOnFailureListener(
   newOnFailureListener(){
   @Override
   publicvoidonFailure(@NonNullExceptione){
   // Model couldn’t be downloaded or other internal error.
   // ...
   }
   });

   Language models are around 30MB, so don't download them unnecessarily, and only download them using Wi-Fi unless the user has specified otherwise. You should also delete unneeded models. See Explicitly manage translation models.

3. After you confirm the model has been downloaded, pass a string of text in the source language to translate():

   Kotlin

   englishGermanTranslator.translate(text)
   .addOnSuccessListener{translatedText->
   // Translation successful.
   }
   .addOnFailureListener{exception->
   // Error.
   // ...
   }

   Java

   englishGermanTranslator.translate(text)
   .addOnSuccessListener(
   newOnSuccessListener(){
   @Override
   publicvoidonSuccess(@NonNullStringtranslatedText){
   // Translation successful.
   }
   })
   .addOnFailureListener(
   newOnFailureListener(){
   @Override
   publicvoidonFailure(@NonNullExceptione){
   // Error.
   // ...
   }
   });

   The translated text, in the target language you configured, is passed to the success listener.

4. Ensure that the close() method is called when the Translator object will no longer be used.

   If you are using a Translator in a Fragment or AppCompatActivity, one easy way to do that is call LifecycleOwner.getLifecycle() on the Fragment or AppCompatActivity, and then call Lifecycle.addObserver. For example:

   Kotlin

   valoptions=...
   valtranslator=Translation.getClient(options)
   getLifecycle().addObserver(translator)

   Java

   TranslatorOptionsoptions=...
   Translatortranslator=Translation.getClient(options);
   getLifecycle().addObserver(translator);
   ...usetranslator...

   Note that this assumes that the code is inside of a class that implements LifecycleOwner (e.g. a Fragment or AppCompatActivity).

Explicitly manage translation models

When you use the translation API as described above, ML Kit automatically downloads language-specific translation models to the device as required. You can also explicitly manage the translation models you want available on the device by using ML Kit's translation model management API. This can be useful if you want to download models ahead of time, or delete unneeded models from the device.

valmodelManager=RemoteModelManager.getInstance()
// Get translation models stored on the device.
modelManager.getDownloadedModels(TranslateRemoteModel::class.java)
.addOnSuccessListener{models->
// ...
}
.addOnFailureListener{
// Error.
}
// Delete the German model if it's on the device.
valgermanModel=TranslateRemoteModel.Builder(TranslateLanguage.GERMAN).build()
modelManager.deleteDownloadedModel(germanModel)
.addOnSuccessListener{
// Model deleted.
}
.addOnFailureListener{
// Error.
}
// Download the French model.
valfrenchModel=TranslateRemoteModel.Builder(TranslateLanguage.FRENCH).build()
valconditions=DownloadConditions.Builder()
.requireWifi()
.build()
modelManager.download(frenchModel,conditions)
.addOnSuccessListener{
// Model downloaded.
}
.addOnFailureListener{
// Error.
}

RemoteModelManagermodelManager=RemoteModelManager.getInstance();
// Get translation models stored on the device.
modelManager.getDownloadedModels(TranslateRemoteModel.class)
.addOnSuccessListener(newOnSuccessListener<Set
>(){
@Override
publicvoidonSuccess(Set
models){
// ...
}
})
.addOnFailureListener(newOnFailureListener(){
@Override
publicvoidonFailure(@NonNullExceptione){
// Error.
}
});
// Delete the German model if it's on the device.
TranslateRemoteModelgermanModel=
newTranslateRemoteModel.Builder(TranslateLanguage.GERMAN).build();
modelManager.deleteDownloadedModel(germanModel)
.addOnSuccessListener(newOnSuccessListener(){
@Override
publicvoidonSuccess(Voidv){
// Model deleted.
}
})
.addOnFailureListener(newOnFailureListener(){
@Override
publicvoidonFailure(@NonNullExceptione){
// Error.
}
});
// Download the French model.
TranslateRemoteModelfrenchModel=
newTranslateRemoteModel.Builder(TranslateLanguage.FRENCH).build();
DownloadConditionsconditions=newDownloadConditions.Builder()
.requireWifi()
.build();
modelManager.download(frenchModel,conditions)
.addOnSuccessListener(newOnSuccessListener(){
@Override
publicvoidonSuccess(Voidv){
// Model downloaded.
}
})
.addOnFailureListener(newOnFailureListener(){
@Override
publicvoidonFailure(@NonNullExceptione){
// Error.
}
});