行驶距离值不正确

Question

使用corelocation框架的新手可以帮助理解为什么我的代码无法正常工作。 我希望它跟踪行进的距离，但是当视图启动时，它每次都会执行不同的操作。 有时，它会跳到1000或另一个较大的值，或者会以随机增量增加。 谁能看到为什么此代码对我不起作用？

    - (void)viewDidLoad
{
    locationManager = [[CLLocationManager alloc] init];
    locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    locationManager.delegate = self;
    locationManager.distanceFilter = 100; //update every 100 meters
    [locationManager startUpdatingLocation];
    startLocation = nil;

    [super viewDidLoad];
    // Do any additional setup after loading the view.
}
-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    if (startLocation == nil)
    {
        totalDistanceBetween = 0;
        self.startLocation = newLocation;
    }
    CLLocationDistance distanceBetween = [newLocation distanceFromLocation:startLocation ];
    startLocation = newLocation;
    totalDistanceBetween += distanceBetween;
    totalDistanceBetween = totalDistanceBetween * 0.001; //convert to m value to km
    NSString *tripString = [[NSString alloc]
                            initWithFormat:@"%.02f",
                            totalDistanceBetween];
    distance.text = tripString;
}

Answer 1

让我startLocation的第一件事是，您告诉位置管理器开始提供更新后 ，将startLocation设置为nil 。

根据startLocation的定义/初始化/重用方式，它可能不包含您期望的初始值。