Rork アプリで Bluetooth Low Energy（BLE）通信を実装する — react-native-ble-plx で IoT デバイスと連携

import { PermissionsAndroid, Platform } from "react-native";
 
// Android 12 以降と 11 以前で必要な権限が変わる
async function requestBlePermissions(): Promise<boolean> {
  if (Platform.OS !== "android") return true;
 
  const apiLevel = Platform.Version as number;
  const perms =
    apiLevel >= 31
      ? [
          PermissionsAndroid.PERMISSIONS.BLUETOOTH_SCAN,
          PermissionsAndroid.PERMISSIONS.BLUETOOTH_CONNECT,
          PermissionsAndroid.PERMISSIONS.ACCESS_FINE_LOCATION,
        ]
      : [PermissionsAndroid.PERMISSIONS.ACCESS_FINE_LOCATION];
 
  const results = await PermissionsAndroid.requestMultiple(perms);
  return Object.values(results).every(
    (r) => r === PermissionsAndroid.RESULTS.GRANTED,
  );
}
// 期待動作: 権限が全て許可されたとき true、ひとつでも拒否されたとき false を返す

import { useEffect, useRef, useState } from "react";
import { BleManager, Device } from "react-native-ble-plx";
 
export function useBleScanner(targetName: string) {
  const managerRef = useRef<BleManager | null>(null);
  const [device, setDevice] = useState<Device | null>(null);
  const [error, setError] = useState<string | null>(null);
 
  useEffect(() => {
    const manager = new BleManager();
    managerRef.current = manager;
 
    const start = async () => {
      const ok = await requestBlePermissions();
      if (!ok) {
        setError("Bluetooth/Location 権限が許可されていません");
        return;
      }
 
      manager.startDeviceScan(null, null, (err, scanned) => {
        if (err) {
          setError(err.message);
          return;
        }
        if (scanned?.name === targetName) {
          manager.stopDeviceScan();
          scanned
            .connect()
            .then((d) => d.discoverAllServicesAndCharacteristics())
            .then(setDevice)
            .catch((e) => setError(String(e)));
        }
      });
    };
 
    start();
 
    return () => {
      manager.stopDeviceScan();
      manager.destroy();
    };
  }, [targetName]);
 
  return { device, error };
}
// 期待動作: targetName と一致する BLE デバイスを発見したら接続し、device を state にセットする

import { Buffer } from "buffer";
 
// 受信: Base64 → バイト配列
const value = await device.readCharacteristicForService(
  serviceUUID,
  characteristicUUID,
);
const bytes = Buffer.from(value.value ?? "", "base64");
console.log("Heart rate:", bytes[1]); // 例: HRP プロファイルの 2 バイト目
 
// 送信: バイト配列 → Base64
const payload = Buffer.from([0x01, 0x02, 0x03]).toString("base64");
await device.writeCharacteristicWithResponseForService(
  serviceUUID,
  characteristicUUID,
  payload,
);
// 期待動作: 受信側 console に Heart rate の数値が出力され、送信は writeCharacteristicWithResponseForService の Promise が resolve する