Identify graphics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 // Copyright 2023 Esri // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License.  import ArcGIS import SwiftUI  struct IdentifyGraphicsView: View {  /// A map with a topographic basemap.  @State private var map = Map(basemapStyle: .arcGISTopographic)   /// A graphics overlay containing a yellow polygon graphic.  @State private var graphicsOverlay = {  let graphicsOverlay = GraphicsOverlay()   // Create a polygon from a list of points.  let polygon = Polygon(points: [  Point(x: -20e5, y: 20e5),  Point(x: 20e5, y: 20e5),  Point(x: 20e5, y: -20e5),  Point(x: -20e5, y: -20e5)  ])   // Create a graphic of the polygon and add it to the overlay.  let polygonGraphic = Graphic(geometry: polygon)  graphicsOverlay.addGraphic(polygonGraphic)   // Create a renderer using a simple fill symbol.  let polygonSymbol = SimpleFillSymbol(style: .solid, color: .yellow)  graphicsOverlay.renderer = SimpleRenderer(symbol: polygonSymbol)   return graphicsOverlay  }()   /// The tap location's screen point used in the identify operation.  @State private var tapScreenPoint: CGPoint?   /// A Boolean value indicating whether to show identify result alert.  @State private var isShowingIdentifyResultAlert = false   /// The message shown in the identify result alert.  @State private var identifyResultMessage = "" {  didSet { isShowingIdentifyResultAlert = identifyResultMessage.isNotEmpty }  }   /// The error shown in the error alert.  @State private var error: Error?   var body: some View {  MapViewReader { mapViewProxy in  MapView(map: map, graphicsOverlays: [graphicsOverlay])  .onSingleTapGesture { screenPoint, _ in  tapScreenPoint = screenPoint  }  .task(id: tapScreenPoint) {  guard let tapScreenPoint else { return }   do {  // Identify the screen point on the graphics overlay using the proxy.  // Use `identifyGraphicsOverlays` instead if you need to identify on  // all the graphics overlay present in the map view.  let identifyResult = try await mapViewProxy.identify(  on: graphicsOverlay,  screenPoint: tapScreenPoint,  tolerance: 12  )   // Display an alert if any graphics were found at the screen point.  if identifyResult.graphics.isNotEmpty {  identifyResultMessage = "Tapped on \(identifyResult.graphics.count) graphic(s)."  }  } catch {  // Show an error alert for an error thrown while identifying.  self.error = error  }   self.tapScreenPoint = nil  }  .alert(  "Identify Result",  isPresented: $isShowingIdentifyResultAlert,  actions: {},  message: { Text(identifyResultMessage) }  )  .errorAlert(presentingError: $error)  }  } }  private extension Collection {  /// A Boolean value indicating whether the collection is not empty.  var isNotEmpty: Bool {  !self.isEmpty  } }  #Preview {  IdentifyGraphicsView() }