nodejs-mobile-react-native

Upon installation, the plugin creates a nodejs-assets/nodejs-project/ directory in your application. This directory is packaged with your app and contains the Node.js logic.

• Entry Point: The background project starts using the main.js file located inside nodejs-assets/nodejs-project/.
• Initial Setup: The directory includes sample-main.js and sample-package.json. It is recommended to rename these to main.js and package.json to begin development.
• Warning: The sample-* files will be overwritten during plugin updates. Do not store custom logic in the sample files; move them to main.js.
• Dependencies: You can add Node modules by running npm install inside the nodejs-assets/nodejs-project/ folder (provided a package.json exists).
• Persistence Warning: The project folder is overwritten during application updates. Do not use this folder for persistent storage.

// Example sample-main.js content
var rn_bridge = require('rn-bridge');

// Echo every message received from react-native.
rn_bridge.channel.on('message', (msg) => {
  rn_bridge.channel.send(msg);
} );

// Inform react-native node is initialized.
rn_bridge.channel.send("Node was initialized.");

The rn-bridge module provides two primary channels for communication between the Node.js environment and the React Native application layer:

1. app (SystemChannel): A reserved, one-way channel used by the React Native native layer to send system events (like pause or resume) to Node.js. It also provides access to the application's data directory.
2. channel (EventChannel): A user-defined event channel used to exchange arbitrary, serializable JavaScript objects between Node.js and React Native.

To use these, import the module in your Node.js code. Note that all data sent through these channels must be serializable via JSON.stringify() (functions are not supported).

const bridge = require('rn-bridge');

// Sending a custom event from Node.js to React Native
bridge.channel.post('myCustomEvent', { foo: 'bar', count: 42 });

// Listening for events in Node.js (emitted from React Native)
bridge.channel.on('someEventFromRN', (data) => {
  console.log('Received:', data);
});

// Accessing the persistent data directory
const dataDir = bridge.app.datadir();

The plugin provides a default eventChannel (accessible via nodejs.channel) to facilitate asynchronous communication. You can send messages from React Native to Node.js and listen for events sent from Node.js to React Native.

Sending messages from React Native to Node.js

Use nodejs.channel.post(event, ...msg) to send a named event and any number of serializable arguments to the Node.js side. For backward compatibility, nodejs.channel.send(...msg) is also available, which sends a 'message' event.

Receiving messages from Node.js in React Native

Since the eventChannel extends EventEmitter, you can use .addListener(event, callback) to listen for specific event names sent from the Node.js side.

Note: All data sent must be serializable via JSON.stringify(). Functions cannot be sent.

const nodejs = require('nodejs-mobile-react-native');

// 1. Listen for events from Node.js
nodejs.channel.addListener('myEvent', (data1, data2) => {
  console.log('Received from Node:', data1, data2);
});

// 2. Send an event to Node.js
nodejs.channel.post('requestData', { id: 123 });

The nodejs object provides methods to control the Node.js runtime and communicate between the React Native layer and the Node.js thread.

Runtime Control

• nodejs.start(scriptFileName, [options]): Starts the runtime with a specific file from the nodejs-project directory.
• nodejs.startWithArgs(command, [options]): Starts the runtime and passes arguments (e.g., command = 'main.js --arg1').
• nodejs.startWithScript(scriptBody, [options]): Starts the runtime using a raw string as the script body.

Communication (Channel)

The nodejs.channel object inherits from React Native's EventEmitter. It allows sending serialized JSON data between layers.

• nodejs.channel.addListener(event, callback): Registers a listener for events raised from the Node.js side.
• nodejs.channel.post(event, ...message): Raises a user-defined event on the Node.js side.
• nodejs.channel.send(...message): An alias for nodejs.channel.post('message', ...message). Used to send messages to the 'message' event.

StartupOptions

Both start methods accept an optional options object:

• redirectOutputToLogcat (boolean, default: true): If false, prevents Node stdout/stderr from being redirected to Android logcat.