Question

我正在制作一个跟踪用户走的路线的应用。我为 horizontalAccuracy > 0的每个位置更新都删除了 MKPointAnnotation 。然后，我尝试从一个点到另一个绘制一条 MKPolyline 。从按下开始按钮开始。在按下开始按钮之前， MKMapView 显示当前位置，这是正确的。当我按下开始按钮时，我希望看到点注释和从一个点到另一个点绘制的多段线。

但是，按开始键时，我会看到一条从UTC坐标（赤道和UTC子午线）绘制到我当前位置的折线。

使用 NSLog 打印时， CLLocationManager 的

didUpdateLocation 委托调用不报告任何此类位置。这是代码...

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations;
{
    CLLocationCoordinate2D coordinates[locations.count];
    int index=0;
    for (CLLocation *location in locations)
    {
        #ifdef DEBUG
        NSLog(@"received co-ordinates:\nlatitude:%f \nlongitude:%f",location.coordinate.latitude,location.coordinate.longitude);
        #endif
        
        [self centerMapWithCoordinates:location.coordinate];
        
        
        // Add an annotation
        if (location.horizontalAccuracy>0)
        {
            MKPointAnnotation *point = [[MKPointAnnotation alloc] init];
            point.coordinate = location.coordinate;
//            if (location.speed>0)
//            {
                point.title = [NSString stringWithFormat:@"%0.2f Kmph",(location.speed*3600/1000)];
//            }
            [self centerMapWithCoordinates:location.coordinate];
            [mapView addAnnotation:point];
            CLLocationCoordinate2D coordinate = location.coordinate;
            coordinates[index] = coordinate;
            index++;
        }
    }
    
    MKPolyline *polyline = [MKPolyline polylineWithCoordinates:coordinates count:index+1];
    [mapView addOverlay:polyline];

}

- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay;
{
    if ([overlay isKindOfClass:[MKPolyline class]])
    {
        MKPolylineRenderer *renderer = [[MKPolylineRenderer alloc] initWithPolyline:overlay];

        renderer.strokeColor = [[UIColor orangeColor] colorWithAlphaComponent:0.7];
        renderer.lineWidth   = 3;

        return renderer;
    }

    return nil;
}

我在做什么错？如何摆脱不必要的折线？

如果您提供代码，请在ObjC中这样做。谢谢。

注意：

在浏览应用程序后，我注意到所有选定的坐标（通过图钉注释显示）相对于上述相同的UTC坐标都有一条折线。看到这张图片...

Answer 1

即使在Apple开发者论坛上，我也无法找到答案。我与Apple开设了一个技术支持实例，结果证明我正在增加将C数组的大小设置为所需值的索引，从而导致从坐标（0.0，0.0）绘制折线。

我将代码更改为此...

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations;
{
#ifdef DEBUG
    NSLog(@"locations array %@",locations);
#endif
    for (int i=0; i<locations.count;i++)
    {
        if (i+1 <locations.count) {
            if (locations[i].horizontalAccuracy>locations[i+1].horizontalAccuracy) {
                currentLocation = locations[i+1];
            }
        }
        else
        {
            currentLocation = locations[i];
        }
        
    }
    
#ifdef DEBUG
    NSLog(@"current location: %@",currentLocation);
#endif
    [locationArray addObject:currentLocation];
    [self centerMapWithCoordinates:currentLocation.coordinate];
    MKPointAnnotation *point = [[MKPointAnnotation alloc] init];
    point.coordinate = currentLocation.coordinate;
    [mapView addAnnotation:point];
    CLLocationCoordinate2D coordinates[2];
    if (previousLocation!=nil)
    {
        coordinates[0]= previousLocation.coordinate;
        coordinates[1]=currentLocation.coordinate;
        MKPolyline *polyline = [MKPolyline polylineWithCoordinates:coordinates count:2];
        [mapView addOverlay:polyline];
    }
    else
    {
        previousLocation=[currentLocation copy];
    }
    
    

}

跟踪用户位置。 MKPolyline从UTC坐标（0，0）绘制到当前位置

1 个答案: