Created
May 14, 2021 09:05
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Custom PagingView in SwiftUI
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struct PagingView<Content>: View where Content: View { | |
@Binding var index: Int | |
let maxIndex: Int | |
let content: () -> Content | |
@State private var offset = CGFloat.zero | |
@State private var dragging = false | |
init(index: Binding<Int>, maxIndex: Int, @ViewBuilder content: @escaping () -> Content) { | |
self._index = index | |
self.maxIndex = maxIndex | |
self.content = content | |
} | |
var body: some View { | |
ZStack(alignment: .bottomLeading) { | |
GeometryReader { geometry in | |
ScrollView(.horizontal, showsIndicators: false) { | |
HStack(spacing: 0) { | |
self.content() | |
.frame(width: geometry.size.width, height: geometry.size.height) | |
.clipped() | |
} | |
} | |
.content.offset(x: self.offset(in: geometry), y: 0) | |
.frame(width: geometry.size.width, alignment: .leading) | |
.gesture( | |
DragGesture().onChanged { value in | |
self.dragging = true | |
self.offset = -CGFloat(self.index) * geometry.size.width + value.translation.width | |
} | |
.onEnded { value in | |
let predictedEndOffset = -CGFloat(self.index) * geometry.size.width + value.predictedEndTranslation.width | |
let predictedIndex = Int(round(predictedEndOffset / -geometry.size.width)) | |
self.index = self.clampedIndex(from: predictedIndex) | |
withAnimation(.easeOut) { | |
self.dragging = false | |
} | |
} | |
) | |
} | |
.clipped() | |
PageControl(index: $index, maxIndex: maxIndex) | |
} | |
} | |
func offset(in geometry: GeometryProxy) -> CGFloat { | |
if self.dragging { | |
return max(min(self.offset, 0), -CGFloat(self.maxIndex) * geometry.size.width) | |
} else { | |
return -CGFloat(self.index) * geometry.size.width | |
} | |
} | |
func clampedIndex(from predictedIndex: Int) -> Int { | |
let newIndex = min(max(predictedIndex, self.index - 1), self.index + 1) | |
guard newIndex >= 0 else { return 0 } | |
guard newIndex <= maxIndex else { return maxIndex } | |
return newIndex | |
} | |
} | |
struct PageControl: View { | |
@Binding var index: Int | |
let maxIndex: Int | |
private var isCurrentIndex: Bool { | |
index == self.index | |
} | |
var body: some View { | |
HStack(spacing: 8) { | |
ForEach(0...maxIndex, id: \.self) { index in | |
Circle() | |
.fill(isCurrentIndex ? Color.white : Color.gray) | |
.frame( | |
width: isCurrentIndex ? 8 : 5, | |
height: isCurrentIndex ? 8 : 5 | |
) | |
} | |
} | |
.padding(15) | |
} | |
} | |
struct PagingView_Previews: PreviewProvider { | |
static var previews: some View { | |
PagingView(index: .constant(2), maxIndex: 5) { | |
Text("Hello") | |
} | |
} | |
} |
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