我对双指滑动（滚动）手势很感兴趣。
不是双指拖动，而是双指滑动（不需要按下）。就像在Safari中用于上下滚动一样。
因为我发现基本手势中没有任何一个适合此操作：TapGesture-不是；LongPressGesture-不是；DragGesture-不是；MagnificationGesture-不是；RotationGesture-不是；
有人有什么想法如何实现这个功能吗？
我至少需要一个方向来参考。
//
// ContentView.swift
// ScrollTest
//
// Created by TR Solutions on 6/9/21.
//
import SwiftUI
/// How the view passes events back to the representable view.
protocol ScrollViewDelegateProtocol {
/// Informs the receiver that the mouse’s scroll wheel has moved.
func scrollWheel(with event: NSEvent);
}
/// The AppKit view that captures scroll wheel events
class ScrollView: NSView {
/// Connection to the SwiftUI view that serves as the interface to our AppKit view.
var delegate: ScrollViewDelegateProtocol!
/// Let the responder chain know we will respond to events.
override var acceptsFirstResponder: Bool { true }
/// Informs the receiver that the mouse’s scroll wheel has moved.
override func scrollWheel(with event: NSEvent) {
// pass the event on to the delegate
delegate.scrollWheel(with: event)
}
}
/// The SwiftUI view that serves as the interface to our AppKit view.
struct RepresentableScrollView: NSViewRepresentable, ScrollViewDelegateProtocol {
/// The AppKit view our SwiftUI view manages.
typealias NSViewType = ScrollView
/// What the SwiftUI content wants us to do when the mouse's scroll wheel is moved.
private var scrollAction: ((NSEvent) -> Void)?
/// Creates the view object and configures its initial state.
func makeNSView(context: Context) -> ScrollView {
// Make a scroll view and become its delegate
let view = ScrollView()
view.delegate = self;
return view
}
/// Updates the state of the specified view with new information from SwiftUI.
func updateNSView(_ nsView: NSViewType, context: Context) {
}
/// Informs the representable view that the mouse’s scroll wheel has moved.
func scrollWheel(with event: NSEvent) {
// Do whatever the content view wants
// us to do when the scroll wheel moved
if let scrollAction = scrollAction {
scrollAction(event)
}
}
/// Modifier that allows the content view to set an action in its context.
func onScroll(_ action: @escaping (NSEvent) -> Void) -> Self {
var newSelf = self
newSelf.scrollAction = action
return newSelf
}
}
/// Our SwiftUI content view that we want to be able to scroll.
struct ContentView: View {
/// The scroll offset -- when this value changes the view will be redrawn.
@State var offset: CGSize = CGSize(width: 0.0, height: 0.0)
/// The SwiftUI view that detects the scroll wheel movement.
var scrollView: some View {
// A view that will update the offset state variable
// when the scroll wheel moves
RepresentableScrollView()
.onScroll { event in
offset = CGSize(width: offset.width + event.deltaX, height: offset.height + event.deltaY)
}
}
/// The body of our view.
var body: some View {
// What we want to be able to scroll using offset(),
// overlaid (must be on top or it can't get the scroll event!)
// with the view that tracks the scroll wheel.
Image(systemName:"applelogo")
.scaleEffect(20.0)
.frame(width: 200, height: 200, alignment: .center)
.offset(offset)
.overlay(scrollView)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
import Combine
@main
struct MyApp: App {
@State var subs = Set<AnyCancellable>() // Cancel onDisappear
@SceneBuilder
var body: some Scene {
WindowGroup {
SomeWindowView()
/////////////
// HERE!!!!!
/////////////
.onAppear { trackScrollWheel() }
}
}
}
/////////////
// HERE!!!!!
/////////////
extension MyApp {
func trackScrollWheel() {
NSApp.publisher(for: \.currentEvent)
.filter { event in event?.type == .scrollWheel }
.throttle(for: .milliseconds(200),
scheduler: DispatchQueue.main,
latest: true)
.sink {
if let event = $0 {
if event.deltaX > 0 { print("right") }
if event.deltaX < 0 { print("left") }
if event.deltaY > 0 { print("down") }
if event.deltaY < 0 { print("up") }
}
}
.store(in: &subs)
}
}
上下滚动是使用 NSPanGestureRecognizer。它有一个 numberOfTouchesRequired 属性，可以让您通过两个手指来响应它。
Mac OS 没有滑动手势识别器。
标准的 UISwipeGestureRecognizer 正好符合您的需求。只需将 numberOfTouchesRequired 设置为 2。
...虽然我不确定移动 Safari 是否使用滑动手势。它可能是带有一些特殊编码的双指拖动。
NSViewRepresentable协议，您可以通过在其onAppear方法中添加以下内容来处理滚动事件：MyRepresentableView()
.onAppear {
NSEvent.addLocalMonitorForEvents(matching: [.scrollWheel]) { event in
print("dx = \(event.deltaX) dy = \(event.deltaY)")
return event
}
}