DragGesture/拖动手势 的使用

1. DragGesture 拖动手势操作

  1.1 实现

/// 拖动手势
struct DragGestureBootcamp: View {
    @State var offset: CGSize = .zero
    
    var body: some View {
        //dragGesture1
        dragGesture2
    }
    
    /// 方式二
    var dragGesture2: some View{
        ZStack {
            VStack {
                Text("\(offset.width)")
                Spacer()
            }
            
            RoundedRectangle(cornerRadius: 20)
                .frame(width: 300, height: 500)
                .offset(offset)
                .scaleEffect(getScaleAmount())
                .rotationEffect(Angle(degrees: getRotationAmount()))
                .gesture(
                    DragGesture()
                        .onChanged{ value in
                            withAnimation(.spring()){
                                offset = value.translation
                            }
                        }
                        .onEnded{ value in
                            withAnimation(.spring()){
                                offset = .zero
                            }
                        }
                )
        }
    }
    
    /// 获取缩放因子
    func getScaleAmount() -> CGFloat{
        // 最大值
        let max = UIScreen.main.bounds.width / 2
        // 当前数值
        let currentAmount = abs(offset.width)
        // 百分比
        let percentage = currentAmount / max
        return 1.0 - min(percentage, 0.5) * 0.5
    }
    
    /// 获取旋转因子
    func getRotationAmount() -> Double{
        // 最大值
        let max = UIScreen.main.bounds.width / 2
        // 当前数值
        let currentAmount = offset.width
        // 百分比
        let percentage = currentAmount / max
        // 转换 Double
        let percentageAsDouble = Double(percentage)
        // 最大角度
        let maxAngle: Double = 10
        return percentageAsDouble * maxAngle
    }
    
    /// 方式一
    var dragGesture1: some View{
        RoundedRectangle(cornerRadius: 20)
            .frame(width: 100, height: 100)
            .offset(offset)
            .gesture(
                DragGesture()
                    .onChanged{ value in
                        withAnimation(.spring()){
                            offset = value.translation
                        }
                    }
                    .onEnded{ value in
                        withAnimation(.spring()){
                            offset = .zero
                        }
                    }
            )
    }
}

  1.2 效果图:

      

2. DragGesture 拖动手势2操作

  2.1 实现

/// 拖动手势2
struct DragGestureBootcamp2: View {
    @State var startingOffsetY: CGFloat = UIScreen.main.bounds.height * 0.85
    @State var currentDragOffsetY: CGFloat = 0
    @State var endingOffsetY: CGFloat = 0
    
    var body: some View {
        ZStack{
            Color.orange.ignoresSafeArea()
            MySignUpView()
                .offset(y: startingOffsetY)
                .offset(y: currentDragOffsetY)
                .offset(y: endingOffsetY)
                .gesture(
                    DragGesture()
                        .onChanged{ value in
                            // 添加动画
                            withAnimation(.spring()){
                                currentDragOffsetY = value.translation.height
                            }
                        }
                        .onEnded{ value in
                            withAnimation(.spring()){
                                if currentDragOffsetY < -150{
                                    endingOffsetY =  -startingOffsetY
                                } else if endingOffsetY != 0 && currentDragOffsetY > 150{
                                    endingOffsetY = 0
                                }
                                currentDragOffsetY = 0
                            }
                        })
            Text("\(currentDragOffsetY)")
        }
        .ignoresSafeArea(edges: .bottom)
    }
}

struct MySignUpView: View {
    var body: some View {
        VStack(spacing: 20){
            Image(systemName: "chevron.up")
                .padding(.top)
            
            Text("Sign up")
                .font(.headline)
                .fontWeight(.semibold)
            
            Image(systemName: "flame.fill")
                .resizable()
                .scaledToFit()
                .frame(width: 100, height: 100)
            
            Text("This is the decription for our app. This is my favorite SwiftUI course and I recommend to all of my friends to subscribe to Swiftful Thinking!")
                .multilineTextAlignment(.center)
            
            Text("Create an account")
                .foregroundColor(.white)
                .font(.headline)
                .padding()
                .padding(.horizontal)
                .background(Color.black.cornerRadius(10))
            Spacer()
        }
        .frame(maxWidth: .infinity)
        .background(Color.white)
        .cornerRadius(30)
    }
}

  2.2 效果图: