Question

我有一个可以从外部设备读取数据的应用程序。这些数据如加速度，陀螺仪，磁力计和压力。

我正在尝试以这种方式读取数据：

async setupNotifications2(device) {
    let i = 0
    const service = this.serviceGeneral();
    while(i<10 ) {
      i++
      const promises = [
        device.readCharacteristicForService(service, this.AccGyrMg),
        device.readCharacteristicForService(service, this.Pressure)
      ]
      Promise.all(promises)
      .then((values) => {
        // const time = new Date().getMilliseconds()
        const time = bufAccGyrMg.readInt16LE(0);
        const [...acc_sx] = [0,2, 4, 6].map(index => bufAccGyrMg.readInt16LE(index));
        this.setState(state => ({acc_sx,array_acc_sx: [...state.array_acc_sx,[time , acc_sx]]}));
        const [...gyr_sx] = [8, 10, 12].map(index => bufAccGyrMg.readInt16LE(index));
        this.setState(state => ({gyr_sx,array_gyr_sx: [...state.array_gyr_sx,[time , gyr_sx]]}));
        const [...mg_sx] = [14,16,18].map(index => bufAccGyrMg.readInt16LE(index));
        this.setState(state => ({gyr_sx,array_mg_sx: [...state.array_mg_sx,[time , mg_sx]]}));
        const bufPressure = Buffer.from(values[1].value, "base64");
        const [...pressure_sx] = [0, 2, 4, 6, 8].map(index => bufPressure.readUInt16LE(index)); 
        this.setState(state => ({pressure_sx,array_pressure_sx: [...state.array_pressure_sx,[time, pressure_sx]]}));

      })

    }
  }

现在我已经在一段时间内插入一个条件，只是为了尝试代码。启动应用程序时，出现以下错误：

YellowBox.js：67可能的未处理的承诺拒绝（id：0）： BleError：操作被拒绝

您认为我该怎么办？谢谢。

Answer 1

我对您的代码进行了一些重构，以帮助解决Unhandled Promise Rejection错误并帮助您指出问题所在：

async setupNotifications2(device) {
  //first of all, put everything inside a big try/catch block
  try {
    let i = 0
    const service = this.serviceGeneral();
    while(i<10 ) {
      i++
      const promises = [
        // then make sure every promise passed to Promise.all() catches its own errors
        device.readCharacteristicForService(service, this.AccGyrMg).catch( e => console.log(`err in first readCharacteristicForService `, e)),
        device.readCharacteristicForService(service, this.Pressure).catch( e => console.log(`err in second readCharacteristicForService `, e))
      ]
      // giben you're in an async function, you can do this to simplify a bit your code:
        const values = await Promise.all(promises);    
        // const time = new Date().getMilliseconds()
        const time = bufAccGyrMg.readInt16LE(0);
        // this is an array, no need to overcomplicate with destructuring assignment... you can do the same below
        const acc_sx = [0,2, 4, 6].map(index => bufAccGyrMg.readInt16LE(index));
        this.setState(state => ({acc_sx,array_acc_sx: [...state.array_acc_sx,[time , acc_sx]]}));
        const [...gyr_sx] = [8, 10, 12].map(index => bufAccGyrMg.readInt16LE(index));
        this.setState(state => ({gyr_sx,array_gyr_sx: [...state.array_gyr_sx,[time , gyr_sx]]}));
        const [...mg_sx] = [14,16,18].map(index => bufAccGyrMg.readInt16LE(index));
        this.setState(state => ({gyr_sx,array_mg_sx: [...state.array_mg_sx,[time , mg_sx]]}));
        const bufPressure = Buffer.from(values[1].value, "base64");
        const [...pressure_sx] = [0, 2, 4, 6, 8].map(index => bufPressure.readUInt16LE(index)); 
        this.setState(state => ({pressure_sx,array_pressure_sx: [...state.array_pressure_sx,[time, pressure_sx]]}));


} catch (err){
   console.error(`general error: `, err)
}
}

React中未处理的承诺拒绝

1 个答案: