检测佩戴Apple Watch的人何时跌倒

Question

如果我掉下我的Apple Watch，并在它落地之前接住它，我正在制作的应用程序应该会检测到手表已经掉落。但这是不可能的。下面的代码有什么问题？谢谢!

let motion = CMMotionManager()
if motion.isDeviceMotionAvailable {
     motion.deviceMotionUpdateInterval = 0.1
     motion.startDeviceMotionUpdates()
     if let deviceMotion = motion.deviceMotion {
          let accelerationX = deviceMotion.gravity.x + deviceMotion.userAcceleration.x
          let accelerationY = deviceMotion.gravity.y + deviceMotion.userAcceleration.y
          let accelerationZ = deviceMotion.gravity.z + deviceMotion.userAcceleration.z
          let totalAcceleration = sqrt((accelerationX * accelerationX) + (accelerationY * accelerationY) + (accelerationZ * accelerationZ))

          if totalAcceleration >  9.0 {
               print("Watch has fallen")
          }
    }
    motion.stopDeviceMotionUpdates()
}

Answer 1

motion.deviceMotion将只获取设备运动数据的最新样本。

因此，当您运行它时，它可能只获取一次数据。你可能需要一些像计时器这样的东西来检查加速度。

类似这样的东西(摘自https://developer.apple.com/documentation/coremotion/getting_raw_accelerometer_events)

let motion = CMMotionManager()

func startAccelerometers() {
   // Make sure the accelerometer hardware is available. 
   if self.motion.isAccelerometerAvailable {
      self.motion.accelerometerUpdateInterval = 1.0 / 60.0  // 60 Hz
      self.motion.startAccelerometerUpdates()

      // Configure a timer to fetch the data.
      self.timer = Timer(fire: Date(), interval: (1.0/60.0), 
            repeats: true, block: { (timer) in
         // Get the accelerometer data.
         if let data = self.motion.accelerometerData {
            let x = data.acceleration.x
            let y = data.acceleration.y
            let z = data.acceleration.z

            // Use the accelerometer data in your app.
         }
      })

      // Add the timer to the current run loop.
      RunLoop.current.add(self.timer!, forMode: .defaultRunLoopMode)
   }
}

或者，您也可以将处理程序传递给将根据deviceMotionUpdateInterval调用的startDeviceMotionUpdates。