blocks|key|2349304|text|当您更改MKMapCamera对象的标题，该对象正在查看地图的中心，您正在改变相机围绕该中心点的旋转角度。想象一下，摄像机是用一根绳子绑在中心点上的。照相机只能绕着中心点移动一个圆圈。摄像机围绕中心点移动的距离由摄像机的航向控制。在您的例子中，中心点是帝国大厦，因此更改相机的标题将使相机在帝国大厦周围绕成一个圆圈，同时保持相机面向大楼。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2349305|如果我正确理解您的要求，您希望保持您的相机位置固定，并改变位置显示在地图的中心使用一个标题从相机。要实现这一点，您需要为地图计算一个新的中心坐标。新的中心坐标将是以你的相机为中心的假想圆周上的一个点。圆的半径是地图中心点与照相机之间的距离。|2349306|此计算使用相机的位置、摄像机的航向和距相机的距离来计算将成为地图新中心的纬度和经度坐标。GreatCircle是一个Objective库，它作为执行所需计算的CLLocation的扩展提供了locationWithBearing:distance:方法：|2349307|-+(nonnull+CLLocation+*)locationWithBearing:(CLLocationDirection)bearing
+++++++++++++++++++++++++++++++++++distance:(CLLocationDistance)distance;|code-block|syntax|javascript|2349308|因此，考虑到相机c的位置、航向(方位)+h+(以度计)和距离d+(以米为单位)，地图m的新中心将是(在Swift中)：|2349309|let+m+=+c.locationWithBearing(h,+distance:+d)|2349310|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/library/mac/documentation/MapKit/Reference/MKMapCamera_class/index.html#//apple_ref/occ/cl/MKMapCamera|1|https://github.com/softwarenerd/GreatCircle|2|https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLLocation_Class/index.html#//apple_ref/occ/instp/CLLocation/coordinate^0|4|B|4|B|0|0|0|27|A|2N|T|18|B|1|27|A|2|0|0|8|1|K|1|U|1|16|1|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@$9|17|A|18|1|19]]|E|$]]|$1|F|3|G|5|6|7|1A|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@$9|1G|A|1H|1|1I]|$9|1J|A|1K|1|1L]]|E|$]]|$1|J|3|K|5|L|7|1M|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]|$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|L|7|1W|8|@]|D|@]|E|$M|N]]|$1|S|3|-4|5|6|7|1X|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]|10|$5|V|W|X|E|$Y|11]]|12|$5|V|W|X|E|$Y|13]]]]

When you change the heading of a <a href="https://developer.apple.com/library/mac/documentation/MapKit/Reference/MKMapCamera_class/index.html#//apple_ref/occ/cl/MKMapCamera" rel="nofollow"><code>MKMapCamera</code></a> object that is looking at the center of the map, you are changing the angle of rotation of the camera around that center point. Imagine that the camera is tied to the center point with a piece of string. The camera can only move in a circle around the center point. How far the camera moves around the center point is controlled by the heading of the camera. In your example, the center point is the Empire State building so changing the heading of the camera will move the camera around the Empire State Building in a circle while keeping the camera facing the building.

If I understand your requirement correctly, you want to keep your camera location fixed and change the location shown at the center of the map using a heading from the camera. To accomplish this, you need to calculate a new center coordinate for the map. The new center coordinate will be a point on the circumference of an imaginary circle centered on your camera. The radius of the circle is the distance of the point at the center of the map from the camera.

This calculation uses the location of the camera, the heading from the camera and the distance from the camera to calculate a latitude and longitude coordinate that will be the new center of the map. <a href="https://github.com/softwarenerd/GreatCircle" rel="nofollow">GreatCircle</a> is an Objective-C library that provides the <code>locationWithBearing:distance:</code> method as an extension of <a href="https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLLocation_Class/index.html#//apple_ref/occ/instp/CLLocation/coordinate" rel="nofollow"><code>CLLocation</code></a> that performs the calculation you need:

<pre><code>- (nonnull CLLocation *)locationWithBearing:(CLLocationDirection)bearing
 distance:(CLLocationDistance)distance;
</code></pre>

So, given the location of your camera <code>c</code>, a heading (bearing) <code>h</code> (in degrees) and a distance <code>d</code> (in meters), the new center of the map <code>m</code> will be (in Swift):

<pre><code>let m = c.locationWithBearing(h, distance: d)
</code></pre>

I am trying to use an MKMapView and MKMapCamera. So far I was able to setup everything and configure the Map in 3D mode/flyover.
I am taking for example for the center of my maps the Empire States Building in NYC, and setup my MKMapCamera with the constructor:

<pre><code>public init(lookingAtCenterCoordinate centerCoordinate:
 CLLocationCoordinate2D, fromDistance distance: CLLocationDistance, 
 pitch: CGFloat, heading: CLLocationDirection)
</code></pre>

So I can now see properly at the center the Empire States Building. Now what I would like to be able is to change the 'heading' (CLLocationDirection) of my MKMapCamera to point to a different direction: meaning not having at the center the Empire States Building.

Right now if I change the heading on the camera, it will in fact move the camera around and still keep the Empire States Building at the center of my MKMapView. 

Looking at the various API, I can't find what API could be using to 'recompute' the new MKMapView center after changing the heading. 

I would like to get the opposite behavior of the current MKMapView where I want my MKMapCamera to be fixed where the center of the map is moving according to the heading I specify. 

What will be the proper way to achieve that?

MKMapCamera changing heading to look at different map center

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试使用MKMapView和MKMapCamera。到目前为止，我能够设置一切，并在3D模式/天桥配置地图。例如，我的地图中心是纽约帝国大厦，并使用构造函数设置了我的MKMapCamera：public init(lookingAtCenterCoordinate centerCoordinate:   CLLo...

MKMapCamera更改标题以查看不同的地图中心-腾讯云开发者社区-腾讯云

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