将 MKPolygon Objective-C 代码转换为 Swift答案

【问题标题】：Converting MKPolygon Objective-C code to Swift将 MKPolygon Objective-C 代码转换为 Swift
【发布时间】：2015-01-29 06:46:44
【问题描述】：

我有以下 Objective-C 方法：

- (void)addPolygonToMap {
    NSInteger numberOfPoints = [self.coordinates count];
    
    if (numberOfPoints > 4) {
        CLLocationCoordinate2D points[numberOfPoints];
        for (NSInteger i = 0; i < numberOfPoints; i++) {
            points[i] = [self.coordinates[i] MKCoordinateValue];
        }
        
        self.polygon = [MKPolygon polygonWithCoordinates:points count:numberOfPoints];
        [self.mapView addOverlay: self.polygon];
    }
    
    self.isDrawingPolygon = NO;
    [self.drawPolygonButton setTitle:@"draw" forState:UIControlStateNormal];
    self.canvasView.image = nil;
    [self.canvasView removeFromSuperview];
}

我尝试将其转换为 Swift：

func addPolygonToMap() {
    var numberOfPoints: NSInteger = self.coordinates.count
    
    if (numberOfPoints > 4) {
        var points: [CLLocationCoordinate2D] = []
        var coordsPointer = UnsafeMutablePointer<CLLocationCoordinate2D>.alloc(numberOfPoints)

        for i in 0..<numberOfPoints {
            points.append(coordsPointer[i])
        }
        
        self.polygon = MKPolygon(coordinates: &points, count: numberOfPoints)
        self.mapView.addOverlay(self.polygon)
        
        coordsPointer.dealloc(numberOfPoints)
    }
    
    self.isDrawingPolygon = false
    self.drawPolygonButton.setTitle("Draw", forState: .Normal)
    self.canvasView.image = nil
    self.canvasView.removeFromSuperview()
}

最后，当调用委托方法时，它实际上并没有将overlay 添加到mapView。我什么都看不到。

我假设这是我的 self.addPolytonToMap() 方法，但我不是 100% 确定。整个场景在我的 Objective-C 项目中运行良好。

func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
    if (overlay is MKPolygon) {
        var overlayPathView = MKPolygonRenderer(overlay: overlay)
        overlayPathView.fillColor = UIColor.cyanColor().colorWithAlphaComponent(0.2)
        overlayPathView.strokeColor = UIColor.cyanColor().colorWithAlphaComponent(0.2)
        overlayPathView.lineWidth = 5
        
        return overlayPathView
    } else if (overlay is MKPolyline) {
        var overlayPathView = MKPolylineRenderer(overlay: overlay)
        overlayPathView.strokeColor = UIColor.blueColor().colorWithAlphaComponent(0.7)
        overlayPathView.lineWidth = 5
        
        return overlayPathView
    }
    
    return nil
}

更新：

我刚刚注意到在我的 Objective-C 版本中，points[i].latitude 可以正常通过，但是当我执行以下操作时，我得到了一个奇怪的输出：

println(coordsPointer[i].latitude)

输出：

1.63041663127611e-321

1.64523860065135e-321

1.65511991356818e-321

1.68970450877706e-321

1.7045264781523e-321

1.72922976044436e-321

这可以解释为什么我看不到overlay，但是我对UnsafeMutablePointer<> 的经验有限。

【问题讨论】：

我只是快速浏览了您的代码 - 您似乎正在分配 coordsPointer 并且从未填充它。但是然后您从坐标指针设置点...但实际上您应该必须从 self.coordinates[i] 读取值

标签： objective-c swift mkmapview mkpolygon

【解决方案1】：

通过修改addPolygonToMap()方法修复：

func addPolygonToMap() {
    var numberOfPoints: NSInteger = self.coordinates.count

    if (numberOfPoints > 4) {
        var points: [CLLocationCoordinate2D] = []

        for i in 0..<numberOfPoints {
            points.insert(self.coordinates[i].MKCoordinateValue, atIndex: i)
        }

        self.polygon = MKPolygon(coordinates: &points, count: numberOfPoints)
        self.mapView.addOverlay(self.polygon)
    }

    self.isDrawingPolygon = false
    self.drawPolygonButton.setTitle("Draw", forState: .Normal)
    self.canvasView.image = nil
    self.canvasView.removeFromSuperview()
}

感谢 @Volker 的帮助。

【讨论】：