iOS - 添加和删除 MKCircle 覆盖到 MapView 导致故障

Question

我有一个 map View ，用户可以选择半径来显示区域。我添加一个 MKCircle 作为叠加层。当半径从 30 英里变为 1 英里时，当 MapView 放大时，MKCircle 的周边会出现明显的故障。该故障看起来有点像天赋。仅在放大而不是缩小时才会发生。\

由于缩放不断变化，我在添加另一个覆盖层之前删除了旧的覆盖层，但我认为这不是问题。

如何消除 MapView 缩放变化时圆圈上的故障？

@IBAction func newRadiusButtonTapped(sender: UIButton) {

    // coordinate is the users location and span was 10 miles now it's 1 mile
    let region = MKCoordinateRegionMake(location.coordinate, span)
    mapView.setRegion(region, animated: true)

    let circle = MKCircle(center: location.coordinate, radius: radius)

     // remove old overlay before adding another one
     for overlay in mapView.overlays {
         mapView.remove(overlay)
     }

     view.layoutIfNeeded()
     // mapView.layoutIfNeeded() I tried this but it didn't make a difference
     mapView.add(circle)
}

Answer 1

我找不到导致故障的原因，但我找到了这个委托(delegate)方法 from this answer在mapView区域完成更改后收到通知的mapView上。我在那里添加了覆盖层

func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) { 
}

简单的过程:

我创建了一个 MKCircle 类型的圆形属性？我还创建了 Bool 类型、名为 shouldAddCircle 的属性，并将其设置为 true。按下按钮时，我使用在按钮内创建的 MKCircle 初始化 Circle 属性，并将 shouldAddCircle 设置为 true。在按钮功能内，我删除了所有 map View 叠加层。

在委托(delegate)方法内，我现在检查 shouldAddCircle 属性是否为 true，如果是，则检查以确保 Circle 属性不为零。如果它们匹配，那么我将初始化的圆添加到 map View 中。将圆圈添加到mapView后，我必须将shouldAddCircle设置为false，因为每次用户滚动 map 时，regionDidChangeAnimated都会被调用，并且它会不断向 map 添加叠加层。

这是下面的代码。请务必在 viewDidLoad 中添加 mapView.delegate = self 并在所有内容之前设置 MKMapViewDelegate。

var circle: MKCircle?
var shouldAddCircle = true

@IBAction func newRadiusButtonTapped(sender: UIButton) {

    // coordinate is the users location and span was 10 miles now it's 1 mile
    let region = MKCoordinateRegionMake(location.coordinate, span)
    mapView.setRegion(region, animated: true)

    let circle = MKCircle(center: location.coordinate, radius: radius)

    // set the circle property to match the circle that was just created
    self.circle = circle

    // set this true
    shouldAddCircle = true

    // remove old overlay before adding another one
    for overlay in mapView.overlays {
        mapView.remove(overlay)
    }
}

// this function gets called repeatedly as the mapView is zoomed and/or panned
func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {

    // make sure this is true because that means the user updated the radius
    if shouldAddCircle {

       // make sure the circle isn't ni
       if let circle = self.circle {
           // after the mapView finishes add the circle to it
           mapView.add(circle)

           // set this to false so that this doesn't called again until the user presses the button where they set it to true
           shouldAddCircle = false
       }
    }
}