Question

我能够获得地图视图的可见矩形以及地图视图的中心点和跨度增量也可以从mkmaap视图方法获得：要获得可见性：使用mapView.visibleMapRect。要获得中心点：使用map view.centerCoordinate并获得范围：mapView.region.span被使用。

现在我掌握了所有信息，如何计算可见光半径？任何人都可以详细解释我吗？

我见过this question，但答案是给我跨度而不是可见区域的半径。

Answer 1

要获得半径，请按照以下步骤操作：

- (CLLocationDistance)getRadius
{
    CLLocationCoordinate2D centerCoor = [self getCenterCoordinate];
    // init center location from center coordinate
    CLLocation *centerLocation = [[CLLocation alloc] initWithLatitude:centerCoor.latitude longitude:centerCoor.longitude];

    CLLocationCoordinate2D topCenterCoor = [self getTopCenterCoordinate];
    CLLocation *topCenterLocation = [[CLLocation alloc] initWithLatitude:topCenterCoor.latitude longitude:topCenterCoor.longitude];

    CLLocationDistance radius = [centerLocation distanceFromLocation:topCenterLocation];

    return radius;
}

它将以米返回半径。

获取中心坐标

- (CLLocationCoordinate2D)getCenterCoordinate
{
    return [self.mapView centerCoordinate];
}

获得半径取决于你想获得第二点的位置。让我们走顶级中心

- (CLLocationCoordinate2D)getTopCenterCoordinate
{
    // to get coordinate from CGPoint of your map
    return [self.mapView convertPoint:CGPointMake(self.mapView.frame.size.width / 2.0f, 0) toCoordinateFromView:self.mapView];
}

Answer 2

使用 Swift 3.0 ，您可以使用扩展程序来简化您的生活：

extension MKMapView {

    func topCenterCoordinate() -> CLLocationCoordinate2D {
        return self.convert(CGPoint(x: self.frame.size.width / 2.0, y: 0), toCoordinateFrom: self)
    }

    func currentRadius() -> Double {
        let centerLocation = CLLocation(coordinate: self.centerCoordinate)
        let topCenterCoordinate = self.topCenterCoordinate()
        let topCenterLocation = CLLocation(coordinate: topCenterCoordinate)
        return centerLocation.distance(from: topCenterLocation)
    }

}

使用 Swift 4.0 ：

extension MKMapView {

    func topCenterCoordinate() -> CLLocationCoordinate2D {
        return self.convert(CGPoint(x: self.frame.size.width / 2.0, y: 0), toCoordinateFrom: self)
    }

    func currentRadius() -> Double {
        let centerLocation = CLLocation(latitude: self.centerCoordinate.latitude, longitude: self.centerCoordinate.longitude)
        let topCenterCoordinate = self.topCenterCoordinate()
        let topCenterLocation = CLLocation(latitude: topCenterCoordinate.latitude, longitude: topCenterCoordinate.longitude)
        return centerLocation.distance(from: topCenterLocation)
    }

}

如何从MKmapview的可见区域获取半径？

2 个答案: