Extract Entities with ML Kit on Android

To analyze a piece of text and extract the entities in it, invoke the annotate() method and pass it either the text string or an instance of EntityExtractionParams which can specify additional options such as a reference time, timezone, or a filter to limit the search for a subset of entity types. The API returns a list of EntityAnnotation objects containing information about each entity.

The Entity Extraction base detector assets are statically linked at app build time. They add about 5.6MB to your app.

  • 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 that Google's Maven repository is included in both the buildscript and allprojects sections.
  2. Add the dependency for the ML Kit entity extraction library to your module's app-level gradle file, which is usually named app/build.gradle:

    dependencies {
    // …
    
    implementation 'com.google.mlkit:entity-extraction:16.0.0-beta2'
    }
    

Extract entities

Create an EntityExtractor object, and configure it with EntityExtractorOptions

Kotlin

val entityExtractor =
   EntityExtraction.getClient(
       EntityExtractorOptions.Builder(EntityExtractorOptions.ENGLISH)
           .build())

Java

EntityExtractor entityExtractor =
        EntityExtraction.getClient(
            new EntityExtractorOptions.Builder(EntityExtractorOptions.ENGLISH)
                .build());

EntityExtractorOptions also accepts a user-defined Executor if you need, otherwise it will use default Executor in ML Kit

Ensure the required model has been downloaded to the device.

Kotlin

entityExtractor
  .downloadModelIfNeeded()
  .addOnSuccessListener { _ ->
    /* Model downloading succeeded, you can call extraction API here. */
  }
  .addOnFailureListener { _ -> /* Model downloading failed. */ }

Java

entityExtractor
    .downloadModelIfNeeded()
    .addOnSuccessListener(
        aVoid -> {
          // Model downloading succeeded, you can call the extraction API here. 
        })
    .addOnFailureListener(
        exception -> {
          // Model downloading failed.
        });

After you confirm the model has been downloaded, pass a string or EntityExtractionParams to annotate(). Don’t call annotate() until you know the model is available.

Kotlin

val params =
      EntityExtractionParams.Builder("My flight is LX373, please pick me up at 8am tomorrow.")
        .setEntityTypesFilter((/* optional entity type filter */)
        .setPreferredLocale(/* optional preferred locale */)
        .setReferenceTime(/* optional reference date-time */)
        .setReferenceTimeZone(/* optional reference timezone */)
        .build()
entityExtractor
      .annotate(params)
      .addOnSuccessListener {
        // Annotation process was successful, you can parse the EntityAnnotations list here.
      }
      .addOnFailureListener {
        // Check failure message here.
      }

Java

EntityExtractionParams params = new EntityExtractionParams
        .Builder("My flight is LX373, please pick me up at 8am tomorrow.")
        .setEntityTypesFilter(/* optional entity type filter */)
        .setPreferredLocale(/* optional preferred locale */)
        .setReferenceTime(/* optional reference date-time */)
        .setReferenceTimeZone(/* optional reference timezone */)
        .build();
entityExtractor
        .annotate(params)
        .addOnSuccessListener(new OnSuccessListener<List<EntityAnnotation>>() {
          @Override
          public void onSuccess(List<EntityAnnotation> entityAnnotations) {
            // Annotation process was successful, you can parse the EntityAnnotations list here.
          }
        })
        .addOnFailureListener(new OnFailureListener() {
          @Override
          public void onFailure(@NonNull Exception e) {
            // Check failure message here.
          }
        });

PreferredLocale, ReferenceTime and ReferenceTimeZone will only influence DateTime entities. If these are not explicitly set, they default to values from the user's device.

Loop over the annotation results to retrieve information about the recognized entities.

Kotlin

for (entityAnnotation in entityAnnotations) {
  val entities: List<Entity> = entityAnnotation.entities

  Log.d(TAG, "Range: ${entityAnnotation.start} - ${entityAnnotation.end}")
  for (entity in entities) {
    when (entity) {
      is DateTimeEntity -> {
        Log.d(TAG, "Granularity: ${entity.dateTimeGranularity}")
        Log.d(TAG, "TimeStamp: ${entity.timestampMillis}")
      }
      is FlightNumberEntity -> {
        Log.d(TAG, "Airline Code: ${entity.airlineCode}")
        Log.d(TAG, "Flight number: ${entity.flightNumber}")
      }
      is MoneyEntity -> {
        Log.d(TAG, "Currency: ${entity.unnormalizedCurrency}")
        Log.d(TAG, "Integer part: ${entity.integerPart}")
        Log.d(TAG, "Fractional Part: ${entity.fractionalPart}")
      }
      else -> {
        Log.d(TAG, "  $entity")
      }
    }
  }
}

Java

List<EntityAnnotation> entityAnnotations = /* Get from EntityExtractor */;
for (EntityAnnotation entityAnnotation : entityAnnotations) {
  List<Entity> entities = entityAnnotation.getEntities();

  Log.d(TAG, String.format("Range: [%d, %d)", entityAnnotation.getStart(), entityAnnotation.getEnd()));
  for (Entity entity : entities) {
    switch (entity.getType()) {
      case Entity.TYPE_DATE_TIME:
        DateTimeEntity dateTimeEntity = entity.asDateTimeEntity();
        Log.d(TAG, "Granularity: " + dateTimeEntity.getDateTimeGranularity());
        Log.d(TAG, "Timestamp: " + dateTimeEntity.getTimestampMillis());
      case Entity.TYPE_FLIGHT_NUMBER:
        FlightNumberEntity flightNumberEntity = entity.asFlightNumberEntity();
        Log.d(TAG, "Airline Code: " + flightNumberEntity.getAirlineCode());
        Log.d(TAG, "Flight number: " + flightNumberEntity.getFlightNumber());
      case Entity.TYPE_MONEY:
        MoneyEntity moneyEntity = entity.asMoneyEntity();
        Log.d(TAG, "Currency: " + moneyEntity.getUnnormalizedCurrency());
        Log.d(TAG, "Integer Part: " + moneyEntity.getIntegerPart());
        Log.d(TAG, "Fractional Part: " + moneyEntity.getFractionalPart());
      case Entity.TYPE_UNKNOWN:
      default:
        Log.d(TAG, "Entity: " + entity);
    }
  }
}

Call the close() method when you no longer need the EntityExtractor object. If you are using EntityExtractor in a Fragment or AppCompatActivity, you can call LifecycleOwner.getLifecycle() on the Fragment or AppCompatActivity, and then Lifecycle.addObserver. For example:

Kotlin

val options = …
val extractor = EntityExtraction.getClient(options);
getLifecycle().addObserver(extractor);

Java

EntityExtractorOptions options = …
EntityExtractor extractor = EntityExtraction.getClient(options);
getLifecycle().addObserver(extractor);

Explicitly manage entity extraction models

When you use the entity extraction API as described above, ML Kit automatically downloads language specific models to the device as required (when you call downloadModelIfNeeded()). You can also explicitly manage the models you want available on the device by using ML Kit’s model management API. This can be useful if you want to download models ahead of time. The API also allows you to delete models that are no longer required.

Kotlin

val modelManager = RemoteModelManager.getInstance()

// Get entity extraction models stored on the device.
modelManager.getDownloadedModels(EntityExtractionRemoteModel::class.java)
  .addOnSuccessListener {
    // ...
  }
  .addOnFailureListener({
    // Error.
  })
    
// Delete the German model if it's on the device.
val germanModel =
  EntityExtractionRemoteModel.Builder(EntityExtractorOptions.GERMAN).build()
modelManager.deleteDownloadedModel(germanModel)
  .addOnSuccessListener({
    // Model deleted.
  })
  .addOnFailureListener({
    // Error.
  })
    
// Download the French model.
val frenchModel =
  EntityExtractionRemoteModel.Builder(EntityExtractorOptions.FRENCH).build()
val conditions =
  DownloadConditions.Builder()
    .requireWifi()
    .build()
modelManager.download(frenchModel, conditions)
  .addOnSuccessListener({
    // Model downloaded.
  })
  .addOnFailureListener({
    // Error.
  })

Java

// Get entity extraction models stored on the device.
modelManager.getDownloadedModels(EntityExtractionRemoteModel.class)
    .addOnSuccessListener(new OnSuccessListener<Set<EntityExtractionRemoteModel>>() {
      @Override
      public void onSuccess(Set<EntityExtractionRemoteModel> models) {
        // ...
      }
    })
    .addOnFailureListener(new OnFailureListener() {
      @Override
      public void onFailure(@NonNull Exception e) {
        // Error.
      }
    });

// Delete the German model if it's on the device.
EntityExtractionRemoteModel germanModel = new EntityExtractionRemoteModel.Builder(EntityExtractorOptions.GERMAN).build();
    modelManager.deleteDownloadedModel(germanModel)
        .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.
EntityExtractionRemoteModel frenchModel = new EntityExtractionRemoteModel.Builder(EntityExtractorOptions.FRENCH).build();
    DownloadConditions conditions = new DownloadConditions.Builder()
        .requireWifi()
        .build();
    modelManager.download(frenchModel, conditions)
        .addOnSuccessListener(new OnSuccessListener<Void>() {
          @Override
          public void onSuccess(Void v) {
            // Model downloaded.
          }
        })
        .addOnFailureListener(new OnFailureListener() {
          @Override
          public void onFailure(@NonNull Exception e) {
            // Error.
          }
        });