SwiftUI Map 不以注释为中心

Question

我使用下面的代码来加载地图，但结果出来后，地图仍然以用户位置为中心而不是注释周围，因为我必须滚动到图钉才能看到。

Map(coordinateRegion: $region, showsUserLocation: true, annotationItems: searchResults) { dest in
    MapAnnotation(coordinate: dest.coordinate, anchorPoint: CGPoint(x: 0.5, y: 0.5)) {
            MapPin(coordinate)
    }
}

Answer 1

要更改地图显示的内容，您只需更改region其绑定的 ( coordinateRegion: $region)。改变它center会移动地图。要对缩放进行操作，您必须对span属性进行操作。

我已经建议您将卡移动到searchResults数组的第一个元素：

Map(coordinateRegion: $region, annotationItems: searchResults) {result in
   MapMarker(coordinate: result.coordinate)
}
.onChange(of: searchResults) {newValue in
   if let result = newValue.first {
      region.center = result.coordinate
   }
}

但是，如果您想移动（并放大/缩小）地图以使其包含所有结果：

Map(coordinateRegion: $region, annotationItems: searchResults) { result in
     MapMarker(coordinate: result.coordinate)
}
.onChange(of: searchResults) { _ in
     if !searchResults.isEmpty {
          region = regionThatFitsTo(coordinates: searchResults.map { $0.coordinate })
     }
}

以及计算适合区域的函数：

func regionThatFitsTo(coordinates: [CLLocationCoordinate2D]) -> MKCoordinateRegion {
        var topLeftCoord = CLLocationCoordinate2D(latitude: -90, longitude: 180)
        var bottomRightCoord = CLLocationCoordinate2D(latitude: 90, longitude: -180)
        for coordinate in coordinates {
            topLeftCoord.longitude = fmin(topLeftCoord.longitude, coordinate.longitude)
            topLeftCoord.latitude = fmax(topLeftCoord.latitude, coordinate.latitude)
            bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, coordinate.longitude)
            bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, coordinate.latitude)
        }

        var region: MKCoordinateRegion = MKCoordinateRegion()
        region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5
        region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5
        region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.4
        region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.4
        return region
    }