开发者问题收集

React 中未处理的 Promise 拒绝

2019-09-17
780

我有一个应用程序,可从外部设备读取数据。这些数据包括加速度、陀螺仪、磁力计和压力。

我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,我只需在一段时间内插入一个条件即可尝试该代码。 当我启动应用程序时,我收到此错误:

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

您认为我该怎么办?谢谢。

1个回答

我稍微重构了您的代码,以帮助摆脱 Unhandled Promise Rejection 错误并帮助您指出问题:

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)
}
}
Tudor Constantin
2019-09-17