如何使用 swiftUI 沿自定义路径移动视图/形状?
Posted
技术标签:
【中文标题】如何使用 swiftUI 沿自定义路径移动视图/形状?【英文标题】:How to move a view/shape along a custom path with swiftUI? 【发布时间】:2020-03-04 07:38:51 【问题描述】:似乎没有一种直观的方式可以沿自定义路径移动视图/形状,尤其是弯曲路径。我已经找到了几个 UIKit 库,它们允许视图在 Bézier 路径上移动(DKChainableAnimationKit、TweenKit、Sica 等),但我对使用 UIKit 不太满意,并且一直遇到错误。
目前使用 swiftUI,我正在手动执行此操作:
import SwiftUI
struct ContentView: View
@State var moveX = true
@State var moveY = true
@State var moveX2 = true
@State var moveY2 = true
@State var rotate1 = true
var body: some View
ZStack
Circle().frame(width:50, height:50)
.offset(x: moveX ? 0:100, y: moveY ? 0:100)
.animation(Animation.easeInOut(duration:1).delay(0))
.rotationEffect(.degrees(rotate1 ? 0:350))
.offset(x: moveX2 ? 0:-100, y: moveY2 ? 0:-200)
.animation(Animation.easeInOut(duration:1).delay(1))
.onAppear()
self.moveX.toggle();
self.moveY.toggle();
self.moveX2.toggle();
self.moveY2.toggle();
self.rotate1.toggle();
// self..toggle()
它在某种程度上完成了工作,但灵活性受到严重限制,并且复合延迟很快就会变得一团糟。
如果有人知道我如何获得自定义视图/形状以沿着以下路径行进,我将不胜感激。
Path path in
path.move(to: CGPoint(x: 200, y: 100))
path.addQuadCurve(to: CGPoint(x: 230, y: 200), control: CGPoint(x: -100, y: 300))
path.addQuadCurve(to: CGPoint(x: 90, y: 400), control: CGPoint(x: 400, y: 130))
path.addLine(to: CGPoint(x: 90, y: 600))
.stroke()
我设法找到的最接近的解决方案是在 SwiftUILab 上,但完整的教程似乎只对付费订阅者开放。
类似这样的:
【问题讨论】:
这是我第一次看到“不习惯使用 UIKit”的人。 SwiftUI 真的接管了... 哈哈,是的,我才开始学习 ios 开发,因为 swiftUI 真的让事情变得如此简单。我对 swiftUI 越熟悉,UIKit 就越陌生。 你在这里看到这个答案了吗? ***.com/questions/56879693/… 实际上你需要SwiftUI-Lab Examples的Example9中的FollowEffect
原样(或稍作修改)
它与 UIKit、SwiftUI 或任何其他 UI 无关......了解参数曲线,然后使用您喜欢的任何编程语言实现您的知识。正确答案(尤其是参数曲线组合)超出了简单答案的范围。有很多不同的问题要回答,一一问。
【参考方案1】:
好的,这不简单,但我想帮忙......
在下一个 sn-p(macOS 应用程序)中,您可以看到可以根据需要进行调整的基本元素。
为简单起见,我选择简单的参数曲线,如果您喜欢使用更复杂的(复合)曲线,您必须解决如何将每个段的部分 t(参数)映射到整个曲线的复合 t(和相同必须在部分沿轨道距离与复合轨道沿轨道距离之间进行映射)。
为什么会出现这样的并发症?
飞机位移(恒速)所需的沿航迹距离与参数化曲线定义所依赖的曲线参数t之间存在非线性关系。
先看看结果
接下来看看它是如何实现的。您需要研究此代码,并在必要时研究参数曲线的定义和行为方式。
//
// ContentView.swift
// tmp086
//
// Created by Ivo Vacek on 11/03/2020.
// Copyright © 2020 Ivo Vacek. All rights reserved.
//
import SwiftUI
import Accelerate
protocol ParametricCurve
var totalArcLength: CGFloat get
func point(t: CGFloat)->CGPoint
func derivate(t: CGFloat)->CGVector
func secondDerivate(t: CGFloat)->CGVector
func arcLength(t: CGFloat)->CGFloat
func curvature(t: CGFloat)->CGFloat
extension ParametricCurve
func arcLength(t: CGFloat)->CGFloat
var tmin: CGFloat = .zero
var tmax: CGFloat = .zero
if t < .zero
tmin = t
else
tmax = t
let quadrature = Quadrature(integrator: .qags(maxIntervals: 8), absoluteTolerance: 5.0e-2, relativeTolerance: 1.0e-3)
let result = quadrature.integrate(over: Double(tmin) ... Double(tmax)) _t in
let dp = derivate(t: CGFloat(_t))
let ds = Double(hypot(dp.dx, dp.dy)) //* x
return ds
switch result
case .success(let arcLength, _/*, let e*/):
//print(arcLength, e)
return t < .zero ? -CGFloat(arcLength) : CGFloat(arcLength)
case .failure(let error):
print("integration error:", error.errorDescription)
return CGFloat.nan
func curveParameter(arcLength: CGFloat)->CGFloat
let maxLength = totalArcLength == .zero ? self.arcLength(t: 1) : totalArcLength
guard maxLength > 0 else return 0
var iteration = 0
var guess: CGFloat = arcLength / maxLength
let maxIterations = 10
let maxErr: CGFloat = 0.1
while (iteration < maxIterations)
let err = self.arcLength(t: guess) - arcLength
if abs(err) < maxErr break
let dp = derivate(t: guess)
let m = hypot(dp.dx, dp.dy)
guess -= err / m
iteration += 1
return guess
func curvature(t: CGFloat)->CGFloat
/*
x'y" - y'x"
κ(t) = --------------------
(x'² + y'²)^(3/2)
*/
let dp = derivate(t: t)
let dp2 = secondDerivate(t: t)
let dpSize = hypot(dp.dx, dp.dy)
let denominator = dpSize * dpSize * dpSize
let nominator = dp.dx * dp2.dy - dp.dy * dp2.dx
return nominator / denominator
struct Bezier3: ParametricCurve
let p0: CGPoint
let p1: CGPoint
let p2: CGPoint
let p3: CGPoint
let A: CGFloat
let B: CGFloat
let C: CGFloat
let D: CGFloat
let E: CGFloat
let F: CGFloat
let G: CGFloat
let H: CGFloat
public private(set) var totalArcLength: CGFloat = .zero
init(from: CGPoint, to: CGPoint, control1: CGPoint, control2: CGPoint)
p0 = from
p1 = control1
p2 = control2
p3 = to
A = to.x - 3 * control2.x + 3 * control1.x - from.x
B = 3 * control2.x - 6 * control1.x + 3 * from.x
C = 3 * control1.x - 3 * from.x
D = from.x
E = to.y - 3 * control2.y + 3 * control1.y - from.y
F = 3 * control2.y - 6 * control1.y + 3 * from.y
G = 3 * control1.y - 3 * from.y
H = from.y
// mandatory !!!
totalArcLength = arcLength(t: 1)
func point(t: CGFloat)->CGPoint
let x = A * t * t * t + B * t * t + C * t + D
let y = E * t * t * t + F * t * t + G * t + H
return CGPoint(x: x, y: y)
func derivate(t: CGFloat)->CGVector
let dx = 3 * A * t * t + 2 * B * t + C
let dy = 3 * E * t * t + 2 * F * t + G
return CGVector(dx: dx, dy: dy)
func secondDerivate(t: CGFloat)->CGVector
let dx = 6 * A * t + 2 * B
let dy = 6 * E * t + 2 * F
return CGVector(dx: dx, dy: dy)
class AircraftModel: ObservableObject
let track: ParametricCurve
let path: Path
var aircraft: some View
let t = track.curveParameter(arcLength: alongTrackDistance)
let p = track.point(t: t)
let dp = track.derivate(t: t)
let h = Angle(radians: atan2(Double(dp.dy), Double(dp.dx)))
return Text("?").font(.largeTitle).rotationEffect(h).position(p)
@Published var alongTrackDistance = CGFloat.zero
init(from: CGPoint, to: CGPoint, control1: CGPoint, control2: CGPoint)
track = Bezier3(from: from, to: to, control1: control1, control2: control2)
path = Path( (path) in
path.move(to: from)
path.addCurve(to: to, control1: control1, control2: control2)
)
struct ContentView: View
@ObservedObject var aircraft = AircraftModel(from: .init(x: 0, y: 0), to: .init(x: 500, y: 600), control1: .init(x: 600, y: 100), control2: .init(x: -300, y: 400))
var body: some View
VStack
ZStack
aircraft.path.stroke(style: StrokeStyle( lineWidth: 0.5))
aircraft.aircraft
Slider(value: $aircraft.alongTrackDistance, in: (0.0 ... aircraft.track.totalArcLength))
Text("along track distance")
.padding()
Button(action:
// fly (to be implemented :-))
)
Text("Fly!")
.padding()
struct ContentView_Previews: PreviewProvider
static var previews: some View
ContentView()
如果您担心如何实现“动画”飞机运动,SwiftUI 动画不是解决方案。您必须以编程方式移动飞机。
你必须导入
import Combine
添加到模型
@Published var flying = false
var timer: Cancellable? = nil
func fly()
flying = true
timer = Timer
.publish(every: 0.02, on: RunLoop.main, in: RunLoop.Mode.default)
.autoconnect()
.sink(receiveValue: (_) in
self.alongTrackDistance += self.track.totalArcLength / 200.0
if self.alongTrackDistance > self.track.totalArcLength
self.timer?.cancel()
self.flying = false
)
并修改按钮
Button(action:
self.aircraft.fly()
)
Text("Fly!")
.disabled(aircraft.flying)
.padding()
终于找到了
【讨论】:
感谢您的帮助,比我希望的要复杂得多,但我想一旦我更好地掌握了 swift,我会更好地理解它。 swiftui lab 的文章暂时完成了我正在寻找的工作。 此答案应标记为正确。谢谢你教我正交。【参考方案2】:试试这个:
但是:请注意:这不是在预览中运行,您必须在模拟器/设备上运行
struct MyShape: Shape
func path(in rect: CGRect) -> Path
let path =
Path path in
path.move(to: CGPoint(x: 200, y: 100))
path.addQuadCurve(to: CGPoint(x: 230, y: 200), control: CGPoint(x: -100, y: 300))
path.addQuadCurve(to: CGPoint(x: 90, y: 400), control: CGPoint(x: 400, y: 130))
path.addLine(to: CGPoint(x: 90, y: 600))
return path
struct ContentView: View
@State var x: CGFloat = 0.0
var body: some View
MyShape()
.trim(from: 0, to: x)
.stroke(lineWidth: 10)
.frame(width: 200, height: 200)
.onAppear()
withAnimation(Animation.easeInOut(duration: 3).delay(0.5))
self.x = 1
【讨论】:
我也试过了,但这只会修剪形状/路径,它不会移动任何上面的东西。例如,如果我有一个飞机的系统图标,并且想将它移动/同步到路径,我该怎么做?【参考方案3】:来自 user3441734 的解决方案非常通用且优雅。读者将受益于每一秒思考ParametricCurve
及其弧长和曲率。这是我发现的唯一一种可以在移动时重新定向移动物体(飞机)以指向前方的方法。
Asperi 还在Is it possible to animate view on a certain Path in SwiftUI 中发布了一个有用的解决方案
这是一个用更少的东西做更少的解决方案。它确实使用了 SwiftUI 动画,这是喜忧参半。 (例如,您可以获得更多动画曲线的选择,但在动画完成时您不会收到通知或回调。)它的灵感来自 Asperi 在Problem animating with animatableData in SwiftUI 中的回答。
import SwiftUI
// Use https://www.desmos.com/calculator/cahqdxeshd to design Beziers.
// Pick a simple example path.
fileprivate let W = UIScreen.main.bounds.width
fileprivate let H = UIScreen.main.bounds.height
fileprivate let p1 = CGPoint(x: 50, y: H - 50)
fileprivate let p2 = CGPoint(x: W - 50, y: 50)
fileprivate var samplePath : Path
let c1 = CGPoint(x: p1.x, y: (p1.y + p2.y)/2)
let c2 = CGPoint(x: p2.x, y: (p1.y + p2.y)/2)
var result = Path()
result.move(to: p1)
result.addCurve(to: p2, control1: c1, control2: c2)
return result
// This View's position follows the Path.
struct SlidingSpot : View
let path : Path
let start : CGPoint
let duration: Double = 1
@State var isMovingForward = false
var tMax : CGFloat isMovingForward ? 1 : 0 // Same expressions,
var opac : Double isMovingForward ? 1 : 0 // different meanings.
var body: some View
VStack
Circle()
.frame(width: 30)
// Asperi is correct that this Modifier must be separate.
.modifier(Moving(time: tMax, path: path, start: start))
.animation(.easeInOut(duration: duration), value: tMax)
.opacity(opac)
Button
isMovingForward = true
// Sneak back to p1. This is a code smell.
DispatchQueue.main.asyncAfter(deadline: .now() + duration + 0.1)
isMovingForward = false
label:
Text("Go")
// Minimal modifier.
struct Moving: AnimatableModifier
var time : CGFloat // Normalized from 0...1.
let path : Path
let start: CGPoint // Could derive from path.
var animatableData: CGFloat
get time
set time = newValue
func body(content: Content) -> some View
content
.position(
path.trimmedPath(from: 0, to: time).currentPoint ?? start
)
struct ContentView: View
var body: some View
SlidingSpot(path: samplePath, start: p1)
【讨论】:
以上是关于如何使用 swiftUI 沿自定义路径移动视图/形状?的主要内容,如果未能解决你的问题,请参考以下文章
如何在 SwiftUI 视图中使用自定义 UI 控件,例如 Button?
如何滚动滚动视图以使 TextField 在 SwiftUI 中移动到键盘上方?