如何从View对象调用ContentView函数

Question

我有一个演示来说明我的问题，你可以在下面查看。我想让这个SwipeBar改变主ContentView的背景色，但我不知道该怎么做。我以前使用过ObservableObject来完成类似的事情，但View的不能是ObservableObject类型，所以我不确定如何让这个SwipeBar与创建它的ContentView"通信"。有什么方法可以做到这一点吗？

快速预览此代码的作用：https://i.stack.imgur.com/lXqj1.jpg

整个ContentView.swift:

import SwiftUI
struct ContentView: View {
@State var backGroundColor: Color = .purple
var body: some View {
VStack {
Spacer()
SwipeBar()
Spacer()
}.background(backGroundColor)
}
func changeBackgroundColor(color: Color) {
self.backGroundColor = color
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

整个SwipeBar.swift：

import SwiftUI
struct SwipeBar: View {
@State var draggedOffset = CGSize.zero
@State var greenOpacityLevel: Double = 0.3
@State var redOpacityLevel: Double = 0.3
var body: some View {
ZStack {
ZStack {
HStack {
ZStack {
RoundedRectangle(cornerRadius: 30, style: .continuous)
.fill(Color.green)
.frame(width: 100, height: 70)
Text("GREEN")
.padding(10)
.foregroundColor(.white)
.font(.system(size: 25))
}.padding(.leading, 20)
.opacity(self.greenOpacityLevel)
Spacer()
ZStack {
RoundedRectangle(cornerRadius: 30, style: .continuous)
.fill(Color.red)
.frame(width: 100, height: 70)
Text("RED")
.padding(10)
.foregroundColor(.white)
.font(.system(size: 25))
}.padding(.trailing, 20)
.opacity(self.redOpacityLevel)
}
ZStack {
RoundedRectangle(cornerRadius: 30, style: .continuous)
.fill(Color.blue)
.frame(width: 375, height: 70)
Text("SWIPE LEFT OR RIGHT")
.foregroundColor(.white)
.font(.system(size: 20))
}
.offset(x: self.draggedOffset.width)
.gesture(DragGesture(minimumDistance: 20, coordinateSpace: .local)
.onChanged { value in
self.draggedOffset = value.translation
if self.draggedOffset.width >= 120 {
self.greenOpacityLevel = 1.0
self.draggedOffset.width = 120
} else {
self.greenOpacityLevel = 0.4
}
if self.draggedOffset.width <= -120 {
self.redOpacityLevel = 1.0
self.draggedOffset.width = -120
} else {
self.redOpacityLevel = 0.4
}
}
.onEnded { value in
if self.draggedOffset.width <= -120 {
// Call the ContentView's changeBackGround function and pass in Color.red
print("background should change to red")
}
if self.draggedOffset.width >= 120 {
// Call the ContentView's changeBackGround function and pass in Color.green
print("background should change to green")
}
self.draggedOffset = CGSize.zero
self.redOpacityLevel = 0.4
self.greenOpacityLevel = 0.4
}
)
}
}
}
}

真正的问题在于代码的最后部分。如何调用ContentView的函数来更改背景颜色？

if self.draggedOffset.width <= -120 {
// Call the ContentView's changeBackGround function and pass in Color.red
print("background should change to red")
}
if self.draggedOffset.width >= 120 {
// Call the ContentView's changeBackGround function and pass in Color.green
print("background should change to green")
}

Answer 1

更改SwipeBar以将Binding转换为Color:

struct SwipeBar: View {
@Binding var color: Color
...

然后在SwipeBar:中适当地更新CCD_ 4的值

.onEnded { value in
if self.draggedOffset.width <= -120 { self.color = .red }
else if self.draggedOffset.width >= 120 { self.color = .green }
...
}

在ContentView中，为backGroundColor属性创建一个Binding，并将其传递给SwipeBar:

SwipeBar(color: self.$backGroundColor)