SwiftUI onChange() event doesn't work on TabView when swiping

Question

I would like to change the value of a text when the active tab of a TabView changes. I tried using onChange(of: activeTab, perform: {}) to change the value of the state variable that stores the text but it seems that the closure given to onChange() is never called.

TabView(selection: $activeTab) {
  ForEach(exampleData) {dayMenu in
    DayMenuView(dayMenu: dayMenu)
      .padding([.leading, .bottom, .trailing])
  }
}
.onChange(of: activeTab, perform: { index in
  print(activeTab)
  withAnimation {
    activeDate = dates[1]
  }
})

Text view

Text(activeDate)

State variables

let dates = ["Montag", "Dienstag"]
    
@State private var activeTab: Int = 0
@State private var activeDate = "Montag"

score 15 · Accepted Answer · edited Aug 23 '22 at 08:48

15

Provided code is not testable but I think it is because activeTab is not changed because tab views are not identified, due to tag, so try

TabView(selection: $activeTab) {
  ForEach(exampleData.indices, id: \.self) { index in
    DayMenuView(dayMenu: exampleData[index])
      .padding([.leading, .bottom, .trailing])
      .tag(index)
  }
}
.onChange(of: activeTab, perform: { index in

edited Aug 23 '22 at 08:48

Martijn Pieters

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answered Dec 10 '20 at 17:40

Asperi

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This and the answer [here](https://stackoverflow.com/questions/59157595/how-to-animate-transition-text-value-change-in-swiftui) solved my problem, thanks – derivmug Dec 10 '20 at 20:23

SwiftUI onChange() event doesn't work on TabView when swiping

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