objective-c - 向 MKMapView 添加多个叠加层

Question

我在理解如何向 MKMapView 添加多个叠加层时遇到一些问题。

我跟踪了一个数组路由。跟踪的路线是 CLLocations 数组。所以我有一个数组数组。

我可以走一条路线并将其绘制在 map View 上。但是，我需要将所有路线绘制到 map View 上。

下面是我如何为 1 条路线创建 MKPolyline:

-(void) loadRoute
{
    //So we grab an array that holds all the locations of one route. 
            NSArray *locations = [[NSArray alloc] initWithArray:[routesArray objectAtIndex:0]];

            // while we create the route points, we will also be calculating the bounding box of our route
            // so we can easily zoom in on it. 
            MKMapPoint northEastPoint; 
            MKMapPoint southWestPoint; 

            // create a c array of points. 
            MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) *[locations count]);

            for(int idx = 0; idx < [locations count]; idx++)
            {
                CLLocation *tempLoc = (CLLocation*)[locations objectAtIndex:idx];

                CLLocationDegrees latitude  = tempLoc.coordinate.latitude;
                CLLocationDegrees longitude = tempLoc.coordinate.longitude;

                // create our coordinate and add it to the correct spot in the array 
                CLLocationCoordinate2D coordinate = CLLocationCoordinate2DMake(latitude, longitude);

                MKMapPoint point = MKMapPointForCoordinate(coordinate);

                // if it is the first point, just use them, since we have nothing to compare to yet. 
                if (idx == 0) {
                    northEastPoint = point;
                    southWestPoint = point;
                }
                else 
                {
                    if (point.x > northEastPoint.x) 
                        northEastPoint.x = point.x;
                    if(point.y > northEastPoint.y)
                        northEastPoint.y = point.y;
                    if (point.x < southWestPoint.x) 
                        southWestPoint.x = point.x;
                    if (point.y < southWestPoint.y) 
                        southWestPoint.y = point.y;
                }
                pointArr[idx] = point;
            }


            self.routeLine = [MKPolyline polylineWithPoints:pointArr count:[locations count]];

//Zoom in to fit route on screen
            _routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);

            // clear the memory allocated earlier for the points
            free(pointArr);

}

这是返回叠加层的 MapKit 委托(delegate)调用:

#pragma mark MKMapViewDelegate

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKOverlayView* overlayView = nil;

    if(overlay == self.routeLine)
    {
        //if we have not yet created an overlay view for this overlay, create it now. 
        if(nil == self.routeLineView)
        {
            self.routeLineView = [[MKPolylineView alloc] initWithPolyline:self.routeLine];
            self.routeLineView.fillColor = [UIColor redColor];
            self.routeLineView.strokeColor = [UIColor redColor];
            self.routeLineView.lineWidth = 3;
        }
        overlayView = self.routeLineView;
    }

    return overlayView;
}

所以上面给出的所有代码都可以正常工作。我不知道如何加载更多叠加层以显示其他路线。

我认为也许在 loadRoute 方法中，遍历所有路由并为每个路由创建一个 MKOverlayView。将所有这些 MKOverlayView 存储在一个数组中然后执行:[self.mapView addOverlays:array];

但它不起作用。问题是在委托(delegate)方法中我不知何故需要知道要返回哪个叠加层。

所以如果我可以按照以下方式做一些事情:

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    int tag = overlay.tag;
    return (MKOverlayView*)[arrayOfViews objectAtIndex:tag];
}

它会工作得很好。但不幸的是，它不是那样工作的:(

任何帮助将不胜感激!

编辑:

我在 ViewDidLoad 中使用它来添加叠加层:

[self loadRoute];

        // add the overlay to the map
        if (nil != self.routeLine) {
            [self.mapView addOverlay:self.routeLine];
        }

        // zoom in on the route. 
        [self zoomInOnRoute];

这是在标题中:

// the data representing the route points. 
    MKPolyline* _routeLine;

    // the view we create for the line on the map
    MKPolylineView* _routeLineView;

    // the rect that bounds the loaded points
    MKMapRect _routeRect;

Answer 1

routeLine 和 routeLineView 变量一次只能指向一个叠加层和叠加层 View ，因此理论上您需要一组此类变量。

但是，根据显示的代码，您不需要首先保留对这些的引用。

我建议删除 routeLine 和 routeLineView 变量。

然后您只需在本地创建一个覆盖对象，并在 viewForOverlay 中返回请求的 overlay 参数的 View 。

在loadRoute 方法中，您可以循环遍历routesArray 并为每个路由创建一个本地覆盖对象，然后调用addOverlay

还有一种更简单的方法来构建一个包含所有路线的 map 矩形，这样您就可以设置 map 的区域以显示所有路线。

例子:

-(void) loadRoute
{
    _routeRect = MKMapRectNull;

    for (int raIndex = 0; raIndex < routesArray.count; raIndex++) 
    {
        //So we grab an array that holds all the locations of one route. 
        NSArray *locations = [[NSArray alloc] initWithArray:
                                 [routesArray objectAtIndex:raIndex]];
        //note we are getting object at raIndex (not 0) above

        //...no change to existing code here...

        //self.routeLine = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
        //replace above line with this...
        MKPolyline *pl = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
        [mapView addOverlay:pl];

        //Zoom in to fit route on screen
        //_routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);
        //replace above line with this to create a rect around ALL routes...
        if (MKMapRectIsNull(_routeRect))
            _routeRect = pl.boundingMapRect;
        else
            _routeRect = MKMapRectUnion(_routeRect, pl.boundingMapRect);

        // clear the memory allocated earlier for the points
        free(pointArr);
    }    
}

在viewDidLoad中，只调用loadRoute，不调用addOverlay。

viewForOverlay 方法变得更加简单:

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKPolylineView *pv = [[MKPolylineView alloc] initWithPolyline:overlay];
    pv.fillColor = [UIColor redColor];
    pv.strokeColor = [UIColor redColor];
    pv.lineWidth = 3;
    return pv;
}

顺便说一下，在 loadRoute 中，这一行:

MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) *[locations count]);

应该是:

MKMapPoint* pointArr = malloc(sizeof(MKMapPoint) *[locations count]);

它应该使用MKMapPoint的大小(不是CLLocationCoordinate2D)。
它们不是一回事(即使结构恰好具有相同的字节大小)。