SwiftUI Map iOS 14 手柄拖动和放大手势
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【中文标题】SwiftUI Map iOS 14 手柄拖动和放大手势【英文标题】:SwifUI Map iOS 14 handle drag and Magnification Gesture 【发布时间】:2021-08-16 10:25:48 【问题描述】:如果用户拖动或缩放地图,我会在地图顶部放置一个小视图,我使用下面的代码来执行此操作,但缩放事件未触发。请帮助我我所缺少的
let drag = DragGesture()
.onChanged( _ in
self.onDragEnded()
)
let pinch = MagnificationGesture()
.onChanged( _ in
self.onDragEnded()
)
@State private var show = false
let combinedGesture = pinch.simultaneously(with: drag)
var body: some View
ZStack
Map(coordinateRegion: $region, showsUserLocation: true, annotationItems: results) dest in
.gesture(combinedGesture)
if show
Color.green
.frame(width: 100, height: 100, alignment: .center)
private func onDragEnded()
show = true
【问题讨论】:
【参考方案1】:当用户拖动和/或缩放地图时,region
会发生变化。你只需要观察MKCoordinateRegion
,或者它的两个属性之一(跨度或中心):
.onChange(of: region.span) _ in
print("regionDidChange")
您使用onChange
观察到的属性必须是Equatable
:
extension MKCoordinateSpan: Equatable
public static func == (lhs: MKCoordinateSpan, rhs: MKCoordinateSpan) -> Bool
lhs.latitudeDelta == rhs.latitudeDelta && lhs.longitudeDelta == rhs.longitudeDelta
编辑:
但是如果你想在位置变化和缩放变化时执行不同的动作,那就更复杂了。因为 1- 缩放级别取决于位置和跨度。 2-当用户放大或缩小时,中心会发生变化(非常轻微) 3-当中心改变时跨度改变(一点)
你可以这样开始:
struct MapView: View
@State private var region = MKCoordinateRegion(center: .init(latitude: 42, longitude: 1.2), span: .init(latitudeDelta: 10, longitudeDelta: 10))
@State private var drag: Int = 0
@State private var pinch: Int = 0
@State private var oldZoomLevel: Double?
var body: some View
ZStack(alignment: Alignment(horizontal: .center, vertical: .top))
GeometryReader proxy in
Map(coordinateRegion: $region)
.onChange(of: region) newRegion in
let zlevel = getZoomLevel(mapWidth: Double(proxy.size.width))
if zlevel != oldZoomLevel
pinch += 1
else
drag += 1
oldZoomLevel = zlevel
HStack
Text(drag.description)
.padding()
.background(Color.pink)
Spacer()
Text(pinch.description)
.padding()
.background(Color.yellow)
func getZoomLevel(mapWidth: Double) -> Double
let MERCATOR_RADIUS = 85445659.44705395
let level = 20.00 - log2(region.span.longitudeDelta * MERCATOR_RADIUS * Double.pi / (180.0 * mapWidth))
return round(level * 100000)/100000
还有扩展:
extension CLLocationCoordinate2D: Equatable
public static func == (lhs: CLLocationCoordinate2D, rhs: CLLocationCoordinate2D) -> Bool
lhs.latitude == rhs.latitude && lhs.longitude == rhs.longitude
extension MKCoordinateSpan: Equatable
public static func == (lhs: MKCoordinateSpan, rhs: MKCoordinateSpan) -> Bool
lhs.latitudeDelta == rhs.latitudeDelta && lhs.longitudeDelta == rhs.longitudeDelta
extension MKCoordinateRegion: Equatable
public static func == (lhs: MKCoordinateRegion, rhs: MKCoordinateRegion) -> Bool
lhs.center == rhs.center && lhs.span == rhs.span
【讨论】:
感谢您的详细解释,缩放和拖动这两个手势我正在做一些动作 2. 我试图观察区域变化,但是当我第一次尝试加载地图时会触发,我想要使用手指对显式用户拖动或缩放执行操作以上是关于SwiftUI Map iOS 14 手柄拖动和放大手势的主要内容,如果未能解决你的问题,请参考以下文章