Tabs and pages in SwiftUI

This week we will talk about creating tabs and pager views in SwiftUI. TabView gained superpower during WWDC20. We can now use it across all the Apple platforms to build tabbed and paged user experiences with SwiftUI out of the box.

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Basics

TabView is a container view that puts children views into separated tabs. Let’s start with a quick example.

import SwiftUI

struct ContentView: View {
    var body: some View {
        TabView {
            Text("Hello")
            Text("World")
        }
    }
}

As you can see, we just wrap our views with TabView, and that’s it. SwiftUI creates a tab-based user interface to switch our views. We can decorate our tabs with text labels and images using the tabItem modifier by adding it to TabView children.

import SwiftUI

struct ContentView: View {
    var body: some View {
        TabView {
            Text("Hello")
                .tabItem {
                    Image(systemName: "heart.fill")
                    Text("Tab1")
                }
            Text("World")
                .tabItem {
                    Text("Tab2")
                }
        }
    }
}

Remember that we can only use Image and Text views inside tabItem closure to decorate our tabs. Sometimes we need to control the selected tab of our TabView to switch it during deep linking or while opening a notification. There is another TabView initializer that we can use to make programmatic tab switching possible.

import SwiftUI

struct ContentView: View {
    @State private var selection = 0

    var body: some View {
        TabView(selection: $selection) {
            Text("Hello")
                .tabItem {
                    Image(systemName: "heart.fill")
                    Text("Tab1")
                }.tag(0)
            Text("World")
                .tabItem {
                    Text("Tab2")
                }.tag(1)
        }
    }
}

As you can see in the example above, we need to provide a selection binding to a TabView. We can change the value of our state property to switch tabs programmatically. We also need to use a tag modifier to provide a value associated with the view. SwiftUI switches tabs using tag value.

Pager view

We can easily replace our tabbed user interface with paged one by applying the tabViewStyle modifier on the view that contains TabView or on TabView itself. Let’s take a look at how we can do that.

struct ContentView: View {
    var body: some View {
        TabView {
            Text("Hello")
            Text("World")
        }.tabViewStyle(PageTabViewStyle(indexDisplayMode: .always))
    }
}

As you can see in the example above, we set an instance of PageTabViewStyle struct as the style of our TabView. We can also control whenever we want to show the page indicator using the indexDisplayMode parameter.

TabView’s selection binding fully supports animations. It means that you can wrap the binding changes using the withAnimation function and programmatically animate page transition. You might need it when your designs contain buttons for the next and previous pages.

import SwiftUI

struct ContentView: View {
    @State private var selection = 0

    var body: some View {
        ZStack(alignment: .bottom) {
            TabView(selection: $selection) {
                Text("Hello").tag(0)
                Text("World").tag(1)
            }.tabViewStyle(PageTabViewStyle(indexDisplayMode: .always))

            Button("next") {
                withAnimation {
                    selection = 1
                }
            }
        }
    }
}

Conclusion

I’m happy to see that this year TabView supports all the platforms. You can use it on watchOS to build a paged user experience or macOS in the settings scene that will apply the correct styling to match the settings screen that we used to see on macOS. It also looks great and adapts to tvOS styling when you use it in a TV app.

I hope you enjoy the post. Feel free to follow me on Twitter and ask your questions related to this article. Thanks for reading, and see you next week!