Use a custom TensorFlow Lite model with Flutter

If your app uses custom TensorFlow Lite models, you can use Firebase ML to deploy your models. By deploying models with Firebase, you can reduce the initial download size of your app and update your app's ML models without releasing a new version of your app. And, with Remote Config and A/B Testing, you can dynamically serve different models to different sets of users.

TensorFlow Lite models

TensorFlow Lite models are ML models that are optimized to run on mobile devices. To get a TensorFlow Lite model:

• Use a pre-built model, such as one of the official TensorFlow Lite models
• Convert a TensorFlow model, Keras model, or concrete function to TensorFlow Lite.

Note that in the absence of a maintained TensorFlow Lite library for Dart, you will need to integrate with the native TensorFlow Lite library for your platforms. This integration is not documented here.

Before you begin

1. Install and initialize the Firebase SDKs for Flutter if you haven't already done so.

2. From the root directory of your Flutter project, run the following command to install the ML model downloader plugin:

   flutter pub add firebase_ml_model_downloader
   

3. Rebuild your project:

   flutter run
   

1. Deploy your model

Deploy your custom TensorFlow models using either the Firebase console or the Firebase Admin Python and Node.js SDKs. See Deploy and manage custom models.

After you add a custom model to your Firebase project, you can reference the model in your apps using the name you specified. At any time, you can deploy a new TensorFlow Lite model and download the new model onto users' devices by calling getModel() (see below).

2. Download the model to the device and initialize a TensorFlow Lite interpreter

To use your TensorFlow Lite model in your app, first use the model downloader to download the latest version of the model to the device. Then, instantiate a TensorFlow Lite interpreter with the model.

To start the model download, call the model downloader's getModel() method, specifying the name you assigned the model when you uploaded it, whether you want to always download the latest model, and the conditions under which you want to allow downloading.

You can choose from three download behaviors:

You should disable model-related functionality—for example, grey-out or hide part of your UI—until you confirm the model has been downloaded.

FirebaseModelDownloader.instance
    .getModel(
        "yourModelName",
        FirebaseModelDownloadType.localModel,
        FirebaseModelDownloadConditions(
          iosAllowsCellularAccess: true,
          iosAllowsBackgroundDownloading: false,
          androidChargingRequired: false,
          androidWifiRequired: false,
          androidDeviceIdleRequired: false,
        )
    )
    .then((customModel) {
      // Download complete. Depending on your app, you could enable the ML
      // feature, or switch from the local model to the remote model, etc.

      // The CustomModel object contains the local path of the model file,
      // which you can use to instantiate a TensorFlow Lite interpreter.
      final localModelPath = customModel.file;

      // ...
    });

Many apps start the download task in their initialization code, but you can do so at any point before you need to use the model.

3. Perform inference on input data

Now that you have your model file on the device you can use it with the TensorFlow Lite interpreter to perform inference. In the absence of a maintained TensorFlow Lite library for Dart, you will need to integrate with the native TensorFlow Lite libraries for iOS and Android.

Appendix: Model security

Regardless of how you make your TensorFlow Lite models available to Firebase ML, Firebase ML stores them in the standard serialized protobuf format in local storage.

In theory, this means that anybody can copy your model. However, in practice, most models are so application-specific and obfuscated by optimizations that the risk is similar to that of competitors disassembling and reusing your code. Nevertheless, you should be aware of this risk before you use a custom model in your app.