我有一个MKMapView和一个MKTileOverlay，因此我可以显示“开放街道地图”图块：

NSString *templateURL = @"http://tile.openstreetmap.org/{z}/{x}/{y}.png";
self.tileOverlay = [[MKTileOverlay alloc] initWithURLTemplate:templateURL];
self.tileOverlay.canreplaceMapContent = YES;
[self.mapView addOverlay:self.tileOverlay level:MKOverlayLevelAboveLabels];

我还想显示一个从我当前位置到库比蒂诺苹果公园的MKPolyline。此折线需要在移动时进行更新，并且由于MKPolyline对象是不可变的，因此我必须将其删除并为每次位置更新添加它：

- (void)locationmanager:(CLLocationmanager *)manager didUpdateLocations:(NSArray*)locations {

    self.currentLocation = userLocation;

    // Update polyline
    CLLocationCoordinate2D applePark = CLLocationCoordinate2DMake(37.334626,-122.008895);
    [self buildPolylineWithDestinationLocation:applePark];

}

- (void)buildPolylineWithDestinationLocation:(CLLocationCoordinate2D)coordinate {

    // Remove the polyline each time so we can redraw it
    if (self.polylineApple) {
        [self.mapView removeOverlay:self.polylineApple];
    }

    // Get current location
    CLLocation *location = self.currentLocation;
    CLLocationCoordinate2D currentLocation = location.coordinate;
    CLLocationCoordinate2D points[2];
    points[0] = currentLocation;
    points[1] = coordinate;

    // Remove all route polylines
    MKPolyline *oldPolyline = self.polylineApple;

    // Draw a line
    self.polylineApple = [MKPolyline polylineWithCoordinates:points count:2];

    [self.mapView addOverlay:self.polylineApple];
    if (oldPolyline) {
        [self.mapView removeOverlay:oldPolyline];
        oldPolyline = nil;
    }

}

问题是，这过去在旧版本的iOS中效果很好，但是自iOS 13以来，这导致每次MKPolyline删除和添加时都会重新绘制图块：

这仅仅是iOS 13的错误，还是我需要在代码中修复某些问题才能使之不再发生？