Enabling in Android Library

caution

This documentation is still experimental and details are subject to changes as we iterate. Feel free to share your feedback on the react-native-website PR for this page.

Moreover, it contains several manual steps. Please note that this won't be representative of the final developer experience once the New Architecture is stable. We're working on tools, templates and libraries to help you get started fast on the New Architecture, without having to go through the whole setup.

Once you have defined the JavaScript specs for your native modules as part of the prerequisites and followed the Android/Gradle setup, you are now ready to migrate your library to the new architecture. Here are the steps you can follow to accomplish this.

1. Configure Codegen in your Gradle File

You can now configure Codegen by specifying the following in the module-level build.gradle file:

react {
    reactRoot = rootProject.file("../node_modules/react-native/")
    jsRootDir = rootProject.file("../js/")
    codegenDir = rootProject.file("../node_modules/react-native-codegen/")
    libraryName = "samplelibrary"
    codegenJavaPackageName = "com.example.samplelibrary"
}

info

Please note that this setup requires you to have the React Gradle Plugin configured in the prerequisite step).

There are three arguments that are required:

• reactRoot: Reference to the react-native package root. Usually located inside ../node_modules/react-native. For third-party NPM libraries that are installed in node_modules, this will be ../react-native.
• jsRootDir: Reference to the directory that contains the JavaScript specs for this library.
• codegenDir: Reference to the react-native-codegen root. Usually located inside ./node_modules/react-native-codegen

These are optional:

• libraryName: Optional. A string that identifies your library. By default, the codegen will use a library name that is derived from the name of the module with a Spec suffix. E.g. for :example:project it will be ExampleProjectSpec).
• codegenJavaPackageName: Optional. A string that represents the Java package your code should use. By default this will be com.facebook.fbreact.specs but you might want to customize it.

The generator will write its output inside the build folder, specifically inside /build/generated/source/codegen

2. Extend or implement the code-generated native interfaces

The JavaScript spec for your native module or component will be used to generate native interface code for each supported platform (i.e. Android and iOS). These native interface files will be generated when a React Native application that depends on your library is built.

While this generated native interface code will not ship as part of your library, you do need to make sure your Java/Kotlin code conforms to the protocols provided by these native interface files.

You can invoke the generateCodegenArtifactsFromSchema Gradle task to generate your library’s native interface code in order to use them as a reference:

./gradlew generateCodegenArtifactsFromSchema

The files that are output can be found inside build/generated/source/codegen and should not be committed, but you’ll need to refer to them to determine what changes you need to make to your native modules in order for them to provide an implementation for each generated interface.

The output of the codegen for a module called NativeAwesomeManager will look like this:

app/build/generated/source/codegen
├── java
│   └── com
│       └── example
│           └── samplelibrary
│               └── NativeAwesomeManagerSpec.java
├── jni
│   ├── Android.mk
│   ├── react
│   │   └── renderer
│   │       └── components
│   │           └── samplelibrary
│   │               ├── ComponentDescriptors.h
│   │               ├── EventEmitters.cpp
│   │               ├── EventEmitters.h
│   │               ├── Props.cpp
│   │               ├── Props.h
│   │               ├── ShadowNodes.cpp
│   │               └── ShadowNodes.h
│   ├── samplelibrary-generated.cpp
│   └── samplelibrary.h
└── schema.json

Extends the abstract class provided by the codegen

Update your native module or component to ensure it extends the abstract class that has been code-generated from your JavaScript specs (i.e. the NativeAwesomeManagerSpec.java file from the previous example).

Following the example set forth in the previous section, your library might import NativeAwesomeManagerSpec, implement the relevant native interface and the necessary methods for it:

import androidx.annotation.NonNull;

import com.example.samplelibrary.NativeAwesomeManagerSpec;
import com.facebook.react.bridge.Promise;
import com.facebook.react.bridge.ReactApplicationContext;

public class NativeAwesomeManager extends NativeAwesomeManagerSpec {

    public static final String NAME = "NativeAwesomeManager";

    public NativeAwesomeManager(ReactApplicationContext reactContext) {
        super(reactContext);
    }

    @Override
    public void getString(String id, Promise promise) {
        // Implement this method
    }

    @NonNull
    @Override
    public String getName() {
        return NAME;
    }
}

Please note that the generated abstract class that you’re now extending (MyAwesomeSpec in this example), is itself extending ReactContextBaseJavaModule. Therefore you should not use access to any of the method/fields you were previously using (e.g. the ReactApplicationContext and so on). Moreover the generated class will now also implement the TurboModule interface for you.