在触发不同的 DragGesture 之前，SwiftUI DragGestures 不会更新

Posted 2023-02-24

【中文标题】在触发不同的 DragGesture 之前，SwiftUI DragGestures 不会更新

【英文标题】：SwiftUI DragGestures not updating until different DragGesture triggered

【发布时间】：2020-02-08 21:19:01

【问题描述】：

这个 gif 应该很清楚地显示了我的问题。

换句话说，我有一个 DragGesture 用于背景颜色，而 TapGesture 用于添加 Text() 视图。每个文本视图上都有一个 DragGesture 以在拖动时更新其位置。 这可行，但在我激活背景颜色 DragGesture 之前，视觉上文本视图位置不会更新。我已经确认文本视图位置值会更新，它们只是不会在视觉上更新。

另外，我有一个长按手势，通过阻止调用 moodColor() 来“锁定”背景颜色。当它被锁定时，文本视图不会移动，直到我再次长按解锁它，然后然后拖动背景颜色。

我有一种误用 DragGestures 的感觉，但显然每个视图都应该有自己的手势。

这里是代码。

class Note : Identifiable
    var id = UUID()
    var text: Text
    var dragOffset : CGPoint
     @GestureState private var location: CGPoint = .zero
    var drag : some Gesture DragGesture(minimumDistance: 0.5, coordinateSpace: .global).onChanged value in self.dragOffset = value.location 
        .updating($location) (value, state, transaction) in state = value.location 
    

    init(textVal: String)
        self.text = Text(textVal).font(.largeTitle)
        self.dragOffset = CGPoint(x: 50, y: 50)
    


struct Col
    var red: Double = 1.0
    var green: Double = 1.0
    var blue: Double = 1.0


struct ContentView: View 
    @State var brightness = 0.9
    @State var color = Col()        // Color Grid Style, RGB
    @GestureState var dragInfo = CGSize.zero
    @State private var myviews: [Note] = []
    @State private var colorLocked = false

    var body: some View 
        return GeometryReader  geo in
            Color.init( red: self.color.red * self.brightness, green: self.color.green * self.brightness, blue: self.color.blue * self.brightness)

                .edgesIgnoringSafeArea(.all)
                .gesture( TapGesture().onEnded value in self.myviews.append(Note(textVal: "A Note")) )
                .gesture( LongPressGesture(minimumDuration: 0.5).onEnded
                            _ in UIImpactFeedbackGenerator(style: .heavy).impactOccurred()
                            self.colorLocked = !self.colorLocked )
                .gesture( DragGesture().onChanged
                            if !self.colorLocked  self.moodColor(data: $0, width: geo.size.width, height: geo.size.height) ) 
                                                  // moodColor() does math to change the background
                .gesture( MagnificationGesture().onChanged
                            self.brightness = Double($0.magnitude + 0.5)
                )

            ForEach(self.myviews)  note in
                note.text.gesture(note.drag).position(note.dragOffset) 
    

【参考方案1】：

保持您的Views 是Views 不在模型class 中

import SwiftUI
class Note : Identifiable
    var id = UUID()
    var dragOffset : CGSize
    var textVal: String
    init(textVal: String)
        self.textVal = textVal
        self.dragOffset = .zero
    


struct Col
    var red: Double = 1.0
    var green: Double = 1.0
    var blue: Double = 1.0

struct AnimatedText: View 
    var note: Note
    @GestureState private var location: CGPoint = .zero
    @State private var offset: CGSize = .zero
    var drag : some Gesture DragGesture()
        .onChanged 
            self.offset.height = self.note.dragOffset.height + $0.translation.height
            self.offset.width = self.note.dragOffset.width + $0.translation.width
    
    .onEnded  _ in
        self.note.dragOffset = self.offset//self.offset = .zero
        
    

    var body: some View 
        Text(note.textVal)
            .font(.largeTitle)
            .offset(x: offset.width, y: offset.height)
            .gesture(drag)
    

struct DragGestureNotMoving: View 
    @State var brightness = 0.9
    @State var color = Col()        // Color Grid Style, RGB
    @GestureState var dragInfo = CGSize.zero
    @State private var myNotes: [Note] = []
    @State private var colorLocked = false
    var body: some View 
        return GeometryReader  geo in
            Color.init( red: self.color.red * self.brightness, green: self.color.green * self.brightness, blue: self.color.blue * self.brightness)

                .edgesIgnoringSafeArea(.all)
                .gesture( TapGesture().onEnded value in self.myNotes.append(Note(textVal: "A Note")) )
                .gesture( LongPressGesture(minimumDuration: 0.5).onEnded
                    _ in UIImpactFeedbackGenerator(style: .heavy).impactOccurred()
                    self.colorLocked = !self.colorLocked )
                //.gesture( DragGesture().onChanged_ in if !self.colorLocked self.moodColor(data: $0, width: geo.size.width, height: geo.size.height) )// moodColor() does math to change the background
                .gesture( MagnificationGesture().onChanged
                    self.brightness = Double($0.magnitude + 0.5)
                )

            ForEach(self.myNotes)  note in
                AnimatedText(note: note)

            

        
    

我评论了moodColor()，因为我没有额外的代码，但移动与更改一起工作。如果您有其他问题，请查看 SimultaneosGesture。

https://developer.apple.com/documentation/uikit/touches_presses_and_gestures/coordinating_multiple_gesture_recognizers/allowing_the_simultaneous_recognition_of_multiple_gestures

【讨论】：

哦，我明白了。所以本质上我需要定义一个自定义视图，并使用它来存储和显示 Note 类。然后将手势附加到新的自定义视图上。