Mkpolyline未被绘制

Question

很明显，这条路线正在制定之中，但没有画出一条折线。我能够找到总距离，并验证了我们使用的坐标不是(0,0)。委托是否有问题，因为似乎addOverlay和addAnnotation (在下面所示的自定义方法中调用createAndAddAnnotationForCoordinate)方法都不起作用？

-(void)viewDidLoad {

[super viewDidLoad];
// Do any additional setup after loading the view.

//generates map view
mapView = [[MKMapView alloc]initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 
self.view.bounds.size.height)];
//setting delegate to self is not fixing the error
mapView.delegate = self;


mapView.mapType = MKMapTypeStandard;




//converting CLLocationCoordinate2D to MKPlacemark
MKPlacemark *startPlacemark = [[MKPlacemark alloc]
initWithCoordinate: addressOneCoords addressDictionary:

[NSDictionary dictionaryWithObjectsAndKeys:nil]];
MKPlacemark *endPlacemark = [[MKPlacemark alloc]initWithCoordinate: addressTwoCoords addressDictionary:[NSDictionary dictionaryWithObjectsAndKeys:nil]];

//converting MKPlacemark to MKMapItem
MKMapItem *start = [[MKMapItem alloc ]initWithPlacemark:startPlacemark];

MKMapItem *end = [[MKMapItem alloc]initWithPlacemark:endPlacemark];


MKDirectionsRequest *request = [MKDirectionsRequest new];
[request setSource:start];
[request setDestination:end];
[request setTransportType:MKDirectionsTransportTypeAutomobile];
request.requestsAlternateRoutes = YES;

//Just to check if the coordinates were transferred successfully between view controllers and they did transfer successfully
NSLog(@"address one lat is %f",addressOneCoords.latitude);
NSLog(@"address one lon is %f",addressOneCoords.longitude);
NSLog(@"address two lat is %f",addressTwoCoords.latitude);
NSLog(@"address two lon is %f",addressTwoCoords.longitude);

MKDirections *directions = [[MKDirections alloc]initWithRequest:request];

[directions calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse response, NSError error){
    //if the route can't be created
    if(error){
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Unable to create route" message:@"Go back to check if addresses are valid" delegate:nil cancelButtonTitle:@"Ok"otherButtonTitles:nil];
        [alert show];
    }
    else{

        [mapView removeOverlays:self.mapView.overlays];

        MKRoute *mainRoute = [response.routes firstObject];



        routeLine = mainRoute.polyline;


        if(routeLine){
            [self.mapView removeOverlay:routeLine];
        }

        //the addOverlay method is not drawing the polyline
        [self.mapView addOverlay: routeLine level:MKOverlayLevelAboveRoads];

        //proof that route is being created successfully
        NSLog(@"Total distance is %f", mainRoute.distance);

        MKMapPoint middlePoint = mainRoute.polyline.points[mainRoute.polyline.pointCount/2];

        //also, the addannotation method is not being called either it seems like
        [self createAndAddAnnotationForCoordinate:MKCoordinateForMapPoint(middlePoint)];


    }
}];


}

我们的createAndAddAnnotationForCoordinate方法，

 -(void) createAndAddAnnotationForCoordinate : (CLLocationCoordinate2D)coordinate{

MKPointAnnotation* annotation = [[MKPointAnnotation alloc]init];
annotation.coordinate = coordinate;
annotation.title = @"Point";
annotation.subtitle = @"subtitle";
[mapView addAnnotation:annotation];


}

我们重写的method委托方法，

-(MKOverlayRenderer )mapView:(MKMapView )mapView rendererForOverlay:(id<MKOverlay>)overlay{

if([overlay isKindOfClass:[MKPolyline class]]){
MKPolylineRenderer *renderer = [[MKPolylineRenderer alloc]initWithOverlay:overlay];
renderer.strokeColor = [UIColor redColor];
renderer.lineWidth = 10.0f;

return renderer;
}

else
    return nil;
}

如果地址一位于NJ中，地址二位于CA中，则输出：

address one lat is 40.902599
address one lon is -74.407097
address two lat is 34.054435
address two lon is -118.253393
Total distance is 4459771.000000

Answer 1

罗恩，我怀疑你的折线(mainRoute.polyline) -你的rendererForOverlay看起来几乎完全像我正在成功使用的。除非出现非常基本的错误，比如没有设置MKMapView委托，或者将其设置为其他对象，否则我几乎可以肯定添加到映射中的polyline不包含有效的CLLocationCoordinate2D结构。

在斯威夫特，创造就像

    var coordinatePtr = UnsafeMutablePointer<CLLocationCoordinate2D>(track2DCoordinates)
    let trackPolygon = MKPolyline(coordinates: coordinatePtr, count: track2DCoordinates.count)
    mapView.removeOverlays(mapView.overlays)
    mapView.addOverlay(trackPolygon)

首先要验证您确实有一个有效的MKPolyline。

我也不确定你的middlePoint计算。

MKMapPoint middlePoint = mainRoute.polyline.points[mainRoute.polyline.pointCount/2];

这类事情现在可能有效，但在Swift中，您需要更加小心用作索引的数据类型。如果你有一个奇数点，或者零呢？