MKMapView 的比例不显示

Question

我正在做一个 iOS 应用程序。在 Xcode 9.1 中，我通过

创建了一个 MKMapView

let mapView = MKMapView(frame: CGRect(x: 0, y: 0, width: view.bounds.width, height: view.bounds.height))
mapView.isUserInteractionEnabled = false
mapView.mapType = .satellite
mapView.showsCompass = false
mapView.showsScale = true
view.addSubview(mapView)

但是当我在模拟器中运行它时，未显示比例，并且我在日志中收到三条消息：

无法从边缘 9 插入指南针

无法从边缘 9 插入比例

无法从角落 4 插入法律归属

指南针没有显示（如预期的那样），但如果我将mapView.showsCompass 更改为trueeither，它也不会显示。但是，会显示 Legal 链接。我在这里想念什么？我猜这与 iOS 11 引入的新安全区域有关，但我看不出这对于我想要覆盖整个屏幕的视图有多重要。

Answer 1

在 iOS 10 或更低版本中

正如@Paulw11 所说，默认情况下仅在缩放时显示比例。

在 iOS 11 中

您可以使用scaleVisibility。 https://developer.apple.com/documentation/mapkit/mkscaleview/2890254-scalevisibility

let scale = MKScaleView(mapView: mapView)
scale.scaleVisibility = .visible // always visible
view.addSubview(scale)

Answer 2

今天的体重秤也有同样的问题。我希望这个比例一直可见。花了我几个小时来解决它。所以我在这里添加代码，以防万一有人遇到同样的问题。

得到一些提示：

来自这个帖子：Use Safe Area Layout programmatically

还有这个网站：Pain Free Constraints with Layout Anchors

编码愉快...

哈迪

// "self.MapOnScreen" refers to the map currently displayed

// check if we have to deal with the scale
if #available(iOS 11.0, *) {

    // as we will change the UI, ensure it's on main thread
    DispatchQueue.main.async(execute: {

        // switch OFF the standard scale (otherwise both will be visible when zoom in/out)
        self.MapOnScreen.showsScale = false

        // build the view
        let scale = MKScaleView(mapView: self.MapOnScreen)

        // we want to use autolayout
        scale.translatesAutoresizingMaskIntoConstraints = false

        // scale should be visible all the time
        scale.scaleVisibility = .visible // always visible

        // add it to the map
        self.MapOnScreen.addSubview(scale)

        // get the current safe area of the map
        let guide = self.MapOnScreen.safeAreaLayoutGuide

        // Activate this array of constraints, which at the time removes leftovers if any
        NSLayoutConstraint.activate(
            [
                // LEFT (I do not want a change if right-to-left language) margin with an offset to safe area
                // alternative would be ".leadingAnchor", which switches to the right margin, if right-to-left language is used        
                scale.leftAnchor.constraint(equalTo: guide.leftAnchor, constant: 16.0),

                // right edge will be the middle of the map
                scale.rightAnchor.constraint(equalTo: guide.centerXAnchor),

                // top margin is the top safe area
                scale.topAnchor.constraint(equalTo: guide.topAnchor),

                // view will be 20 points high
                scale.heightAnchor.constraint(equalToConstant: 20.0)
            ]
        )
    })
}

Answer 3

Objective c 等价物：-

if (@available(iOS 11.0, *)) {
        // switch OFF the standard scale (otherwise both will be visible when zoom in/out)
    self.map.showsScale = false;

        // build the view

    MKScaleView* scale = [MKScaleView scaleViewWithMapView:self.map];

        // we want to use autolayout
    scale.translatesAutoresizingMaskIntoConstraints = false;

        // scale should be visible all the time
    scale.scaleVisibility = MKFeatureVisibilityVisible;// always visible
    
    // add it to the map
    [self.view addSubview:scale];
   
        // get the current safe area of the map
    UILayoutGuide * guide = self.view.safeAreaLayoutGuide;

        // Activate this array of constraints, which at the time removes leftovers if any
        [NSLayoutConstraint activateConstraints:
            @[
                // LEFT (I do not want a change if right-to-left language) margin with an offset to safe area
                // alternative would be ".leadingAnchor", which switches to the right margin, if right-to-left language is used
               //[scale.leftAnchor constraintEqualToAnchor: guide.centerXAnchor constant: -(scale.frame.size.width/2.0)],
          
                // right edge will be the middle of the map
                [scale.rightAnchor constraintEqualToAnchor: guide.centerXAnchor constant: (scale.frame.size.width/2.0)],

                // top margin is the top safe area
                [scale.bottomAnchor constraintEqualToAnchor: guide.bottomAnchor constant:-self.toolBar.frame.size.height],

                // view will be 20 points high
                [scale.heightAnchor constraintEqualToConstant: 50.0]
            ]
        ];
    
    [self.view bringSubviewToFront:scale];
}