You can use ML Kit to translate text between languages. ML Kit
currently supports translation between
59 languages
.
Before you begin
- If you haven't already,
add Firebase to your Android project
.
- Add the dependencies for the ML Kit Android libraries to your module
(app-level) Gradle file (usually
app/build.gradle
):
apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'
dependencies {
// ...
implementation 'com.google.firebase:firebase-ml-natural-language:22.0.0'
implementation 'com.google.firebase:firebase-ml-natural-language-translate-model:20.0.8'
}
Translate a string of text
To translate a string between two languages:
Create a
FirebaseTranslator
object, configuring it with the source and
target languages:
Java
// Create an English-German translator:
FirebaseTranslatorOptions options =
new FirebaseTranslatorOptions.Builder()
.setSourceLanguage(FirebaseTranslateLanguage.EN)
.setTargetLanguage(FirebaseTranslateLanguage.DE)
.build();
final FirebaseTranslator englishGermanTranslator =
FirebaseNaturalLanguage.getInstance().getTranslator(options);
Kotlin+KTX
// Create an English-German translator:
val options = FirebaseTranslatorOptions.Builder()
.setSourceLanguage(FirebaseTranslateLanguage.EN)
.setTargetLanguage(FirebaseTranslateLanguage.DE)
.build()
val englishGermanTranslator = FirebaseNaturalLanguage.getInstance().getTranslator(options)
If you don't know the language of the input text, you can use the
language
identification API
first. (But be sure you
don't keep too many language models on the device at once.)
Make sure the required translation model has been downloaded to the device.
Don't call
translate()
until you know the model is available.
Java
FirebaseModelDownloadConditions conditions = new FirebaseModelDownloadConditions.Builder()
.requireWifi()
.build();
englishGermanTranslator.downloadModelIfNeeded(conditions)
.addOnSuccessListener(
new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void v) {
// Model downloaded successfully. Okay to start translating.
// (Set a flag, unhide the translation UI, etc.)
}
})
.addOnFailureListener(
new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
// Model couldn’t be downloaded or other internal error.
// ...
}
});
Kotlin+KTX
englishGermanTranslator.downloadModelIfNeeded()
.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.
// ...
}
Language models are around 30MB, so don't download them unnecessarily, and
only download them using WiFi, unless the user has specified otherwise. You
should also delete unneeded models.
See
Explicitly manage translation models
.
After you confirm the model has been downloaded, pass a string of text in
the source language to
translate()
:
Java
englishGermanTranslator.translate(text)
.addOnSuccessListener(
new OnSuccessListener<String>() {
@Override
public void onSuccess(@NonNull String translatedText) {
// Translation successful.
}
})
.addOnFailureListener(
new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
// Error.
// ...
}
});
Kotlin+KTX
englishGermanTranslator.translate(text)
.addOnSuccessListener { translatedText ->
// Translation successful.
}
.addOnFailureListener { exception ->
// Error.
// ...
}
The translated text, in the target language you configured, is passed to the
success listener.
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.
Java
FirebaseModelManager modelManager = FirebaseModelManager.getInstance();
// Get translation models stored on the device.
modelManager.getDownloadedModels(FirebaseTranslateRemoteModel.class)
.addOnSuccessListener(new OnSuccessListener<Set<FirebaseTranslateRemoteModel>>() {
@Override
public void onSuccess(Set<FirebaseTranslateRemoteModel> models) {
// ...
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
// Error.
}
});
// Delete the German model if it's on the device.
FirebaseTranslateRemoteModel deModel =
new FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.DE).build();
modelManager.deleteDownloadedModel(deModel)
.addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void v) {
// Model deleted.
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
// Error.
}
});
// Download the French model.
FirebaseTranslateRemoteModel frModel =
new FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.FR).build();
FirebaseModelDownloadConditions conditions = new FirebaseModelDownloadConditions.Builder()
.requireWifi()
.build();
modelManager.download(frModel, conditions)
.addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void v) {
// Model downloaded.
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
// Error.
}
});
Kotlin+KTX
val modelManager = FirebaseModelManager.getInstance()
// Get translation models stored on the device.
modelManager.getDownloadedModels(FirebaseTranslateRemoteModel::class.java)
.addOnSuccessListener { models ->
// ...
}
.addOnFailureListener {
// Error.
}
// Delete the German model if it's on the device.
val deModel = FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.DE).build()
modelManager.deleteDownloadedModel(deModel)
.addOnSuccessListener {
// Model deleted.
}
.addOnFailureListener {
// Error.
}
// Download the French model.
val frModel = FirebaseTranslateRemoteModel.Builder(FirebaseTranslateLanguage.FR).build()
val conditions = FirebaseModelDownloadConditions.Builder()
.requireWifi()
.build()
modelManager.download(frModel, conditions)
.addOnSuccessListener {
// Model downloaded.
}
.addOnFailureListener {
// Error.
}