行駛距離值不正確

Question

使用corelocation框架的新手可以幫助理解為什么我的代碼無法正常工作。 我希望它跟蹤行進的距離，但是當視圖啟動時，它每次都會執行不同的操作。 有時，它會跳到1000或另一個較大的值，或者會以隨機增量增加。 誰能看到為什么此代碼對我不起作用？

    - (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

讓我startLocation的第一件事是，您告訴位置管理器開始提供更新后 ，將startLocation設置為nil 。

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