SwiftUI 实现Draggesture效果

   今天闲来无事，使用SwiftUI 实现拖动，并且返回的动态效果。代码不多。。。。。

效果如下：

代码如下：

1import SwiftUI
2import Combine
3
4class KBDragObjectBind: BindableObject {
5    var didChange = PassthroughSubject<KBDragObjectBind,Never>()
6    var mass:Double = 1.0 {
7        didSet{
8            massString = String(format: "%.2f", mass)
9            self.didChange.send(self)
10        }
11    }
12    var massString = "1.0" {
13        didSet {
14            self.didChange.send(self)
15        }
16    }
17    var stiffness:Double = 100.0 {
18        didSet{
19            stiffnessString = String(format: "%.0f", stiffness)
20            self.didChange.send(self)
21        }
22    }
23    
24    var stiffnessString = "100.0" {
25        didSet {
26            self.didChange.send(self)
27        }
28    }
29    
30    var damping:Double = 10.0 {
31        didSet {
32            dampingString = String(format: "%.0f", damping)
33            self.didChange.send(self)
34        }
35    }
36    var dampingString = "10.0"{
37        didSet {
38            self.didChange.send(self)
39        }
40    }
41    
42    var  initialVelocity:Double = 0.0 {
43        didSet {
44            initialVelocityString = String(format: "%.0f", initialVelocity)
45            self.didChange.send(self)
46        }
47    }
48    var initialVelocityString = "0.0"{
49        didSet{
50            self.didChange.send(self)
51        }
52    }
53}
54
55struct KBDragGestureView : View {
56    @State var offset :CGSize = CGSize(width: 0, height: 0)
57    @ObjectBinding var dragObj = KBDragObjectBind()
58    @State var offset2 :CGSize = CGSize(width: 0, height: 0)
59    
60    var body:some View {
61        VStack {
62            Text("Default Setting")
63            Image(systemName: "hand.draw.fill")
64                .resizable()
65                .frame(width: 100, height: 100)
66                .offset(offset)
67                .gesture(
68                    DragGesture()
69                        .onEnded({ (value) in
70                            print("onEnd:\(value)")
71                            withAnimation(.spring()) {
72                                self.offset = CGSize(width: 0, height: 0)
73                            }
74                        })
75                        .onChanged({ (value) in
76                            print("onChanged: \(value)")
77                            self.offset = value.translation
78                        })
79                ).zIndex(10)
80            Divider()
81            HStack(){
82                Text("质量弥撒曲mass(\(self.dragObj.massString)):")//
83                Slider(value: $dragObj.mass, from: 0.1, through: 1.0, by: 0.01)
84            }
85            HStack(){
86                Text("刚度stiffness(\(self.dragObj.stiffnessString)):")
87                Slider(value: $dragObj.stiffness, from: 0, through: 100.0, by: 1)
88            }
89            HStack(){
90                Text("阻尼dampin(\(self.dragObj.dampingString)):")
91                Slider(value: $dragObj.damping, from: 0, through: 100.0, by: 1)
92            }
93            HStack(){
94                Text("初始速度initialVelocity(\(self.dragObj.initialVelocityString)):")
95                Slider(value: $dragObj.initialVelocity, from: 0.0, through: 100.0, by: 1)
96            }
97            
98            Image(systemName: "hand.draw")
99                .resizable()
100                .frame(width: 100, height: 100)
101                .offset(offset2)
102                .gesture(
103                    DragGesture()
104                        .onEnded({ (value) in
105                            print("onEnd:\(value)")
106                            withAnimation(.spring(mass: self.dragObj.mass,
107                                                  stiffness: self.dragObj.stiffness,
108                                                  damping: self.dragObj.damping,
109                                                  initialVelocity: self.dragObj.initialVelocity)) {
110                                self.offset2 = CGSize(width: 0, height: 0)
111                            }
112                        })
113                        .onChanged({ (value) in
114                            print("onChanged: \(value)")
115                            self.offset2 = value.translation
116                        })
117            )
118            
119            
120        }.padding()
121    }
122}
123
124#if DEBUG
125struct KBDragGestureView_Previews : PreviewProvider {
126    static var previews: some View {
127        KBDragGestureView()
128    }
129}
130#endif