[英]SwiftUI ScrollView with Tap and Drag gesture
我正在尝试实现一个带有可以点击和拖动的元素的 ScrollView。 它应该按以下方式工作:
下面的代码涵盖了所有这些要求(点击指示器除外)。 但是,我不确定它为什么有效,具体来说,为什么我需要使用 .highPriorityGesture,例如不能使用.sequenced(before: ...)
对 Tap Gesture 和 DragGesture 进行排序(这会阻止滚动)。
另外,我想收到触地得分事件的通知(不是触地得分,参见 2.)。 我尝试使用 LongPressGesture() 而不是 TapGesture(),但这也会阻止 ScrollView 滚动并且之后甚至不会触发 DragGesture。
有人知道如何实现吗? 或者这是SwiftUI的限制? 如果是这样,是否可以将 UIKit 的东西移植过来以实现此目的(我也已经尝试过,但没有成功,ScrollView 的内容也应该是动态的,因此移植整个 ScrollView 可能很困难)?
谢谢你的协助!
struct ContentView: View {
var body: some View {
ScrollView() {
ForEach(0..<5, id: \.self) { i in
ListElem()
.highPriorityGesture(TapGesture().onEnded({print("tapped!")}))
.frame(maxWidth: .infinity)
}
}
}
}
struct ListElem: View {
@GestureState var dragging = CGSize.zero
var body: some View {
Circle()
.frame(width: 100, height: 100)
.gesture(DragGesture(minimumDistance: 0, coordinateSpace: .global)
.updating($dragging, body: {t, state, _ in
state = t.translation
}))
.offset(dragging)
}
}
我尝试了几个选项,我认为sequenced
和simultaneously
的组合允许两个手势同时运行。 为了实现 onTouchDown,我使用了最小距离为 0 的DragGesture
。
struct ContentView: View {
var body: some View {
ScrollView() {
ForEach(0..<5, id: \.self) { i in
ListElem()
.frame(maxWidth: .infinity)
}
}
}
}
struct ListElem: View {
@State private var offset = CGSize.zero
@State private var isDragging = false
@GestureState var isTapping = false
var body: some View {
// Gets triggered immediately because a drag of 0 distance starts already when touching down.
let tapGesture = DragGesture(minimumDistance: 0)
.updating($isTapping) {_, isTapping, _ in
isTapping = true
}
// minimumDistance here is mainly relevant to change to red before the drag
let dragGesture = DragGesture(minimumDistance: 0)
.onChanged { offset = $0.translation }
.onEnded { _ in
withAnimation {
offset = .zero
isDragging = false
}
}
let pressGesture = LongPressGesture(minimumDuration: 1.0)
.onEnded { value in
withAnimation {
isDragging = true
}
}
// The dragGesture will wait until the pressGesture has triggered after minimumDuration 1.0 seconds.
let combined = pressGesture.sequenced(before: dragGesture)
// The new combined gesture is set to run together with the tapGesture.
let simultaneously = tapGesture.simultaneously(with: combined)
return Circle()
.overlay(isTapping ? Circle().stroke(Color.red, lineWidth: 5) : nil) //listening to the isTapping state
.frame(width: 100, height: 100)
.foregroundColor(isDragging ? Color.red : Color.black) // listening to the isDragging state.
.offset(offset)
.gesture(simultaneously)
}
}
对于此处感兴趣的任何人来说,自定义滚动视图不会被其中一条评论中提到的其他手势所阻止。 因为这不可能用标准的 ScrollView 来解决。
Github 上 SwiftUI 的 OpenScrollView
归功于
https://stackoverflow.com/a/59897987/12764795 http://developer.apple.com/documentation/swiftui/composing-swiftui-gestures https://www.hackingwithswift.com/books/ios-swiftui/how在 swiftui 中使用手势
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