SwiftUI How to Make Page TabView Dynamic - swiftui

Question

So I am trying to make my TabView height dynamic. I have been looking for a way to do this but I can't seem to find a solution anywhere. This is how my code looks like.
struct ContentView: View {
#State var contentHeight: CGFloat = 0
var body: some View {
NavigationView {
ScrollView {
VStack {
TabView {
TestView1(contentHeight: $contentHeight)
TestView2(contentHeight: $contentHeight)
}
.tabViewStyle(.page)
.frame(height: contentHeight)
.indexViewStyle(.page(backgroundDisplayMode: .always))
.background(.yellow)
}
.navigationBarTitleDisplayMode(.inline)
.navigationTitle("Test Project")
}
}
}
}
This is how my test1view and test2view look like.
struct TestView1: View {
#State var height: CGFloat = 0
#Binding var contentHeight: CGFloat
var body: some View {
Color.red
.frame(maxWidth:.infinity, minHeight: 200, maxHeight: 200)
.background(
GeometryReader { geo in
Color.clear
.preference(
key: HeightPreferenceKey.self,
value: geo.size.height
)
.onAppear {
contentHeight = height
}
}
.onPreferenceChange(HeightPreferenceKey.self) { height in
self.height = height
}
)
}
}
struct TestView2: View {
#Binding var contentHeight: CGFloat
#State var height: CGFloat = 0
var body: some View {
Color.black
.frame(maxWidth:.infinity, minHeight: 350, maxHeight: 350)
.background(
GeometryReader { geo in
Color.clear
.preference(
key: HeightPreferenceKey.self,
value: geo.size.height
)
.onAppear {
contentHeight = height
}
}
.onPreferenceChange(HeightPreferenceKey.self) { height in
self.height = height
}
)
}
}
struct HeightPreferenceKey: PreferenceKey {
static let defaultValue: CGFloat = 0
static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
value = nextValue()
}
}
Now the problem is that when I drag it just a little the height changes. So when I drag it a little to the left the height changes to the height of TestView2 and it is still on TestView1.
I tried to add a drag gesture but it didn't let me swipe to the next page. So I don't know how I will be able to achieve this. Ive been looking for a solution but still no luck.

Answer 1

You can use the TabView($selection) initializer to do this. https://developer.apple.com/documentation/swiftui/tabview/init(selection:content:)
It tells you which tab you're currently viewing. Based off the middle point of the screen. And you don't have to deal with nasty GeometryReader and HeightPreferenceKey.
Here's your updated code. I even added a nice animation to fade between the two heights!
struct ContentView: View {
#State var selectedTab: Tab = .first
#State var animatedContentHeight: CGFloat = 300
enum Tab {
case first
case second
var contentHeight: CGFloat {
switch self {
case .first:
return 200
case .second:
return 350
}
}
}
var body: some View {
TabView(selection: $selectedTab) {
TestView1()
.tag(Tab.first)
TestView2()
.tag(Tab.second)
}
.tabViewStyle(.page)
// .frame(height: selectedTab.contentHeight) // Uncomment to see without animation
.frame(height: animatedContentHeight)
.indexViewStyle(.page(backgroundDisplayMode: .always))
.onChange(of: selectedTab) { newValue in
print("now selected:", newValue)
withAnimation { animatedContentHeight = selectedTab.contentHeight }
}
}
}
struct TestView1: View {
var body: some View {
Color.red
}
}
struct TestView2: View {
var body: some View {
Color.black
}
}