微信小程序蓝牙 Roal 适配器

main.js

const rpc = roal.RPC.create(new WxTransport({
  serviceUUID: 'F010',
  characteristicUUID: 'F011'
});

rpc.request('ping').then(result => console.log(result));                           

WxTransport.js

class WxTransport extends roal.Transport {
    constructor(options) {
        super();
        this._buf = [];
        this._serviceUUID = options.serviceUUID;
        this._characteristicUUID = options.characteristicUUID;
        this._deviceId = null; // 扫描连接后，更新此字段
        this.ready = this.setup();
    }
    setup() {
        return new Promise((resolve, reject) => {
          // 扫描蓝牙设备
          // 匹配到对应的设备
          // 连接蓝牙设备，成功后，
            // * 给 this._deviceId 赋值
            // * 调用 onConnect
            // * resolve 这个 Promise
            // * 错误调用 reject
        });
    }
    onConnect() {
        wx.onBLECharacteristicValueChange(c => this.onBLECharacteristicValueChange(c.value));
    }
    onBLECharacteristicValueChange(value) {
        const length = value.length < 0 ? 0 : value.length;
        if (length <= 2) {
            return this._buf = [];
        }
        const offset = value[0] | (value[1] << 8);
        if (this._buf.length !== (offset & 0x7FFF)) {
            return this._buf = [];
        }
        this._buf = this._buf.concat(value.slice(2));
        if (offset & 0x8000) {
            const s = fromUTF8Array(this._buf);
            console.log('received: ' + s);
            this.recv(JSON.parse(s));
            this._buf = [];
        }
    }
    // 这是提供给 RPC 调用的方法
    // * 当调用 rcp.request 时, RPC 会对请求进行封装，并构建 message 对象，此对象格式参见 roal ts 定义；
    // * 然后调用到 transport.send(message) 请求发送数据到目标连接。
    // 此方法直接收一个参数，并返回一个 Promise；
    send(message) {
        return this.ready.then(() => {
            const str = JSON.stringify(message);
            const buffer = new ArrayBuffer(str.length);
            for (let i = 0; i < buffer.byteLength; i++) {
                buffer[i] = str[i];
            }
            wx.writeBLECharacteristicValue({
                deviceId: this._deviceId, // deviceId 需要自行补充，在进行设备扫描和连接时，记录到对象中。
                serviceId: this._serviceUUID,
                characteristicId: this._characteristicUUID,
                value: buffer,
                success: function (res) {
                    console.log(res);
                    console.log('writeBLECharacteristicValue success', res.errMsg);
                }
            });
        });
    }
}
function fromUTF8Array(data) {
    let str = '', i;
    for (i = 0; i < data.length; i++) {
        let value = data[i];
        if (value < 0x80) {
            str += String.fromCharCode(value);
        }
        else if (value > 0xBF && value < 0xE0) {
            str += String.fromCharCode((value & 0x1F) << 6 | data[i + 1] & 0x3F);
            i += 1;
        }
        else if (value > 0xDF && value < 0xF0) {
            str += String.fromCharCode((value & 0x0F) << 12 | (data[i + 1] & 0x3F) << 6 | data[i + 2] & 0x3F);
            i += 2;
        }
        else {
            let charCode = ((value & 0x07) << 18 | (data[i + 1] & 0x3F) << 12 | (data[i + 2] & 0x3F) << 6 | data[i + 3] & 0x3F) - 0x010000;
            str += String.fromCharCode(charCode >> 10 | 0xD800, charCode & 0x03FF | 0xDC00);
            i += 3;
        }
    }
    return str;
}