Adopt the AnimatedImage with Indicator view modifier

Author: dreampiggy

SDWebImageSwiftUI/Classes/AnimatedImage.swift

@@ -11,7 +11,7 @@ import SDWebImage
 
 #if os(iOS) || os(tvOS) || os(macOS)
 
-/// A coordinator object used for `AnimatedImage`native view  bridge for UIKit/AppKit/WatchKit.
+/// A coordinator object used for `AnimatedImage`native view  bridge for UIKit/AppKit.
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public final class AnimatedImageCoordinator: NSObject {
 
@@ -37,6 +37,14 @@ final class AnimatedImageModel : ObservableObject {
     @Published var scale: CGFloat = 1
 }
 
+/// Loading Binding Object, only properties in this object can support changes from user with @State and refresh
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
+final class AnimatedLoadingModel : ObservableObject, IndicatorReportable {
+    @Published var image: PlatformImage? // loaded image, note when progressive loading, this will published multiple times with different partial image
+    @Published var isLoading: Bool = false // whether network is loading or cache is querying, should only be used for indicator binding
+    @Published var progress: Double = 0 // network progress, should only be used for indicator binding
+}
+
 /// Completion Handler Binding Object, supports dynamic @State changes
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 final class AnimatedImageHandler: ObservableObject {
@@ -81,6 +89,7 @@ final class AnimatedImageConfiguration: ObservableObject {
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public struct AnimatedImage : PlatformViewRepresentable {
     @ObservedObject var imageModel = AnimatedImageModel()
+    @ObservedObject var imageLoading = AnimatedLoadingModel()
     @ObservedObject var imageHandler = AnimatedImageHandler()
     @ObservedObject var imageLayout = AnimatedImageLayout()
     @ObservedObject var imageConfiguration = AnimatedImageConfiguration()
@@ -193,18 +202,31 @@ public struct AnimatedImage : PlatformViewRepresentable {
         if currentOperation != nil {
             return
         }
+        self.imageLoading.isLoading = true
         view.wrapped.sd_setImage(with: imageModel.url, placeholderImage: imageConfiguration.placeholder, options: imageModel.webOptions, context: imageModel.webContext, progress: { (receivedSize, expectedSize, _) in
+            let progress: Double
+            if (expectedSize > 0) {
+                progress = Double(receivedSize) / Double(expectedSize)
+            } else {
+                progress = 0
+            }
+            DispatchQueue.main.async {
+                self.imageLoading.progress = progress
+            }
             self.imageHandler.progressBlock?(receivedSize, expectedSize)
         }) { (image, error, cacheType, _) in
             // This is a hack because of Xcode 11.3 bug, the @Published does not trigger another `updateUIView` call
-            // Here I have to use UIKit API to triger the same effect (the window change implicitly cause re-render)
+            // Here I have to use UIKit/AppKit API to triger the same effect (the window change implicitly cause re-render)
             if let hostingView = AnimatedImage.findHostingView(from: view) {
                 #if os(macOS)
                 hostingView.viewDidMoveToWindow()
                 #else
                 hostingView.didMoveToWindow()
                 #endif
             }
+            self.imageLoading.image = image
+            self.imageLoading.isLoading = false
+            self.imageLoading.progress = 1
             if let image = image {
                 self.imageHandler.successBlock?(image, cacheType)
             } else {
@@ -704,7 +726,7 @@ extension AnimatedImage {
     }
 }
 
-// Web Image convenience
+// Web Image convenience, based on UIKit/AppKit API
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
 
@@ -732,6 +754,23 @@ extension AnimatedImage {
     }
 }
 
+// Indicator
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
+extension AnimatedImage {
+    
+    /// Associate a indicator when loading image with url
+    /// - Parameter indicator: The indicator type, see `Indicator`
+    public func indicator<T>(_ indicator: Indicator<T>) -> some View where T : View {
+        return self.modifier(IndicatorViewModifier(reporter: self.imageLoading, indicator: indicator))
+    }
+    
+    /// Associate a indicator when loading image with url, convenient method with block
+    /// - Parameter content: A view that describes the indicator.
+    public func indicator<T>(@ViewBuilder content: @escaping (_ isAnimating: Binding<Bool>, _ progress: Binding<Double>) -> T) -> some View where T : View {
+        return indicator(Indicator(content: content))
+    }
+}
+
 #if DEBUG
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 struct AnimatedImage_Previews : PreviewProvider {

SDWebImageSwiftUI/Classes/ImageManager.swift

@@ -10,7 +10,7 @@ import SwiftUI
 import SDWebImage
 
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
-class ImageManager : ObservableObject {
+class ImageManager : ObservableObject, IndicatorReportable {
     @Published var image: PlatformImage? // loaded image, note when progressive loading, this will published multiple times with different partial image
     @Published var isLoading: Bool = false // whether network is loading or cache is querying, should only be used for indicator binding
     @Published var progress: Double = 0 // network progress, should only be used for indicator binding
@@ -70,9 +70,7 @@ class ImageManager : ObservableObject {
                 // So previous View struct call `onDisappear` and cancel the currentOperation
                 return
             }
-            if let image = image {
-                self.image = image
-            }
+            self.image = image
             self.isIncremental = !finished
             if finished {
                 self.isLoading = false

SDWebImageSwiftUI/Classes/Indicator/Indicator.swift

@@ -17,27 +17,39 @@ public struct Indicator<T> where T : View {
     /// Create a indicator with builder
     /// - Parameter builder: A builder to build indicator
     /// - Parameter isAnimating: A Binding to control the animation. If image is during loading, the value is true, else (like start loading) the value is false.
-    /// - Parameter progress: A Binding to control the progress during loading. Value between [0, 1]. If no progress can be reported, the value is 0.
+    /// - Parameter progress: A Binding to control the progress during loading. Value between [0.0, 1.0]. If no progress can be reported, the value is 0.
     /// Associate a indicator when loading image with url
     public init(@ViewBuilder content: @escaping (_ isAnimating: Binding<Bool>, _ progress: Binding<Double>) -> T) {
         self.content = content
     }
 }
 
+/// A protocol to report indicator progress
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
+public protocol IndicatorReportable : ObservableObject {
+    /// whether indicator is loading or not
+    var isLoading: Bool { get set }
+    /// indicator progress, should only be used for indicator binding, value between [0.0, 1.0]
+    var progress: Double { get set }
+}
+
 /// A implementation detail View Modifier with indicator
 /// SwiftUI View Modifier construced by using a internal View type which modify the `body`
 /// It use type system to represent the view hierarchy, and Swift `some View` syntax to hide the type detail for users
 @available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
-struct IndicatorViewModifier<T> : ViewModifier where T : View {
-    @ObservedObject var imageManager: ImageManager
+public struct IndicatorViewModifier<T, V> : ViewModifier where T : View, V : IndicatorReportable {
+    
+    /// The progress reporter
+    @ObservedObject var reporter: V
 
+    /// The indicator
     var indicator: Indicator<T>
 
-    func body(content: Content) -> some View {
+    public func body(content: Content) -> some View {
         ZStack {
             content
-            if imageManager.isLoading {
-                indicator.content($imageManager.isLoading, $imageManager.progress)
+            if reporter.isLoading {
+                indicator.content($reporter.isLoading, $reporter.progress)
             }
         }
     }

SDWebImageSwiftUI/Classes/WebImage.swift

@@ -280,7 +280,7 @@ extension WebImage {
     /// Associate a indicator when loading image with url
     /// - Parameter indicator: The indicator type, see `Indicator`
     public func indicator<T>(_ indicator: Indicator<T>) -> some View where T : View {
-        return self.modifier(IndicatorViewModifier(imageManager: imageManager, indicator: indicator))
+        return self.modifier(IndicatorViewModifier(reporter: imageManager, indicator: indicator))
     }
 
     /// Associate a indicator when loading image with url, convenient method with block