快速获取行进的总距离ios 9

Question

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [AnyObject]){
    if startLocation == nil {
        startLocation = locations.first as! CLLocation
    }
    else{
        let distance = startLocation.distanceFromLocation(locations.last as! CLLocation)
        let lastDistance = lastLocation.distanceFromLocation(locations.last as! CLLocation)
        traveledDistance += lastDistance
        //print("\(startLocation)")
        //print("\(lastLocation)")
        //print("\(traveledDistance)")
        print("\(distance)")
        distanceLabel.text = "\(distance)"
    }
    lastLocation = locations.last as! CLLocation
}

I found the code above on stackoverflow and its working if i drive or walk in one direction but when i turn around and go back to the start point the distane is 0m.it would be nice if someone could explain the code in detail or give me some advice. thanks

Answer 1

Isn't it trivial? You are printing the distance which is calculated over and over from the startLocation which will never change in your code. If I start in point A and go to B (there will be some distance in meters) and then go back to A and calculate from the startLocation (which is always A ) it should be zero. :D

I didn't try your code but it seems to me this is what happens there. Print traveledDistance instead, this is the value that will always increase as you move around.

Fix your code like this:

print("\(traveledDistance)")
distanceLabel.text = "\(traveledDistance)"

If you only need the total distance I would change the code to look like this:

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [AnyObject]) {

    /* for the ever first call the if check should fail because lastLocation is initially nil in your code (I assume) */
    if lastLocation != nil {

        /* this will start adding a distance at the second call of the callback */
        traveledDistance += lastLocation.distanceFromLocation(locations.last as! CLLocation)

        print("\(traveledDistance)")
        distanceLabel.text = "\(traveledDistance)"
    }

    /* here we are saving the current location to our variable for later calculation */
    lastLocation = locations.last as! CLLocation
}