iOS swift：MKPointAnnotation 并不总是显示标题

Question

我在尝试在 iOS 10 中的 MKMapView 上显示 MKPointAnnotation 时注意到的一个奇怪行为让我头疼不已。我在 StackOverflow 上找到了 2 篇相关帖子，但都没有真正回答我面临的问题。它们是：

1. https://stackoverflow.com/questions/36760810/mkmapview-annotation-title-is-not-showing 但这没有任何答案，而且问题似乎略有不同，因为这里的标题从不显示，而在我的情况下它确实显示但有一个奇怪的解决方法。
2. https://stackoverflow.com/questions/33818285/ios-mapview-annotations-not-showing-for-pins 但用户只是忘记实际设置标题。尽管@rockhammer 在最后有一个有趣的评论，但它有点相关但不完全是：“似乎在将注释添加到地图时，.title 必须至少有一个字符，即使它是“”。否则，即使 .title 随后被修改为非 ""，标签也不会显示。'

我的情况：我有一个功能，当用户长按地图时，将添加注释。标题基本上是使用 CLGeocoder().reverseGeocodeLocation(...) 查找找到的地址的第一个可用行。如果一切都失败了，它将简单地使用日期。您会注意到，只有在绝对确定标题中有文本时，才会一直添加注释。这使得上面提到的第二篇文章的评论不适合这种情况。

我的问题：您会注意到顶部附近的行annotation.title = "BLAH"。如果没有这一行，注释标题将不会显示在 MKMapView 中，而只会显示引脚！

@IBOutlet weak var map: MKMapView!

func longPress(gestureRecognizer: UIGestureRecognizer) {
    if gestureRecognizer.state == UIGestureRecognizerState.began {
        let touchPoint = gestureRecognizer.location(in: self.map)
        let coordinate = map.convert(touchPoint, toCoordinateFrom: self.map)
        let annotation = MKPointAnnotation()
        annotation.coordinate = coordinate
        annotation.title = "BLAH" //WITHOUT THIS THE TITLE NEVER SHOWS

        CLGeocoder().reverseGeocodeLocation(CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)) { (placemarks, error) in
            if error != nil {
                print(error!)
            } else {
                if let placemark = placemarks?[0] {
                    annotation.title = placemark.subThoroughfare != nil ? placemark.subThoroughfare! : ""
                    annotation.title = annotation.title! + (annotation.title! == "" ? "" : " ") + (placemark.thoroughfare != nil ? placemark.thoroughfare! : "")
                    if annotation.title == "" {
                        annotation.title = placemark.subLocality != nil ? placemark.subLocality! : ""
                        if annotation.title == "" {
                            annotation.title = placemark.subAdministrativeArea != nil ? placemark.subAdministrativeArea! : ""
                            if annotation.title == "" {
                                annotation.title = placemark.postalCode != nil ? placemark.postalCode! : ""
                                if annotation.title == "" {
                                    annotation.title = placemark.country != nil ? placemark.country! : ""
                                }
                            }
                        }
                    }
                }
            }
            if annotation.title == "" {
                annotation.title = "Added \(NSDate())"
            } //At this point a title is guaranteed to be set. Still, it never shows unless it is first 'initialised' with 'BLAH' or something at the beginning.
        }

        self.map.addAnnotation(annotation)
    }
}

如果有人可以向我展示这种情况的逻辑以及发生的方式/原因，那就太好了。

Answer 1

您需要更改3个不正确的方法； 我不知道为什么这种方法不起作用。

我向您推荐其他一些编译和工作的方法，通常，很好。你需要：

• 将UIGestureRecognizerState.began改为UIGestureRecognizerState.Began;

• 将touchPoint = gestureRecognizer.location(in: self.map)改为touchPoint = gestureRecognizer.locationInView(self.mapView)；

• 最后，将coordinate = mapView.convert(teste, toCoordinateFrom: self.mapView)更改为coordinate = mapView.convertPoint(touchPoint, toCoordinateFromView: self.mapView)。

最后你的代码应该是这样的：

@IBOutlet weak var map: MKMapView!


func longPress(gestureRecognizer: UIGestureRecognizer) {
    if gestureRecognizer.state == UIGestureRecognizerState.Began {     // And not .began
        let touchPoint: CGPoint = gestureRecognizer.locationInView(self.map)   //And not location(in: self.map)
    //let coordinate = mapView.convert(teste, toCoordinateFrom: self.map)
    let coordinate = map.convertPoint(touchPoint, toCoordinateFromView: self.map)
        let annotation = MKPointAnnotation()
        annotation.coordinate = coordinate
        //annotation.title = "BLAH" //WITHOUT THIS THE TITLE NEVER SHOWS

        CLGeocoder().reverseGeocodeLocation(CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)) { (placemarks, error) in
            if error != nil {
                print(error!)
            } else {
                if let placemark = placemarks?[0] {
                    annotation.title = placemark.subThoroughfare != nil ? placemark.subThoroughfare! : ""
                    annotation.title = annotation.title! + (annotation.title! == "" ? "" : " ") + (placemark.thoroughfare != nil ? placemark.thoroughfare! : "")
                    if annotation.title == "" {
                        annotation.title = placemark.subLocality != nil ? placemark.subLocality! : ""
                        if annotation.title == "" {
                            annotation.title = placemark.subAdministrativeArea != nil ? placemark.subAdministrativeArea! : ""
                            if annotation.title == "" {
                                annotation.title = placemark.postalCode != nil ? placemark.postalCode! : ""
                                if annotation.title == "" {
                                    annotation.title = placemark.country != nil ? placemark.country! : ""
                                }
                            }
                        }
                    }
                }
            }

            if annotation.title == "" {
                annotation.title = "Added \(NSDate())"
            } //At this point a title is guaranteed to be set. Still, it never shows unless it is first 'initialised' with 'BLAH' or something at the beginning.
        }

        self.map.addAnnotation(annotation)
    }
}