Getting started with the SwiftUI NavigationSplitView
SwiftUI 4 adds a new NavigationSplitView component that simplifies creating rich sidebar-based experiences on iPad and macOS, while automatically scaling down to a NavigationStackView (also new) on iPhone. It’s a powerful component that however can be a bit tricky to get started with, so let’s take a look at how to use it and some ways to style it.
Since NavigationSplitView requires some setup that is easy to overlook, this post will do some intentional trial and error, where we will first setup things in a way that will fail, then discuss why it fails before fixing it.
Creating a navigation split view
To serve as a base for the various examples in this post, consider the following basic example, where we have a navigation split view that links to various “demo screens” that are defined by this enum:
enum DemoScreen: String, Codable {
case first, second, third
var title: String {
rawValue.capitalized
}
}
Let’s now create a NavigationSplitView with a sidebar that links to the various screens, as well as a main detail area that displays the currently selected screen:
struct ContentView: View {
@State
private var selection: DemoScreen? = .first
var body: some View {
NavigationSplitView {
sidebarContent
} detail: {
detailContent
}
}
}
sidebarContent is just a List with navigation links to the various screens:
extension ContentView {
var sidebarContent: some View {
List {
link(to: .first)
link(to: .second)
link(to: .third)
}
}
func link(to page: DemoScreen) -> some View {
NavigationLink(value: page) {
Text(page.title)
}
}
}
detailContent switches over the selection, if any, and displays some screen-specific content:
extension ContentView {
@ViewBuilder
var detailContent: some View {
if let selection = selection {
detailContent(for: selection)
.buttonStyle(.bordered)
} else {
Text("No selection")
}
}
@ViewBuilder
func detailContent(for screen: DemoScreen) -> some View {
switch screen {
case .first: Button("First button") {}
case .second: Button("Second button") {}
case .third: Button("Second button") {}
}
}
}
Note that we use a .bordered button style to accentuate the button colors for later examples.
Navigation split view style
If you now run the app on an iPad, it should looks like this when the sidebar is collapsed in landscape:
However, if you now tap the top leading sidebar toggle button, the sidebar may expand as a slid-over:
You may also notice that the sidebar button is missing. These effects are however not consistent. For instance, I sometimes get a non-slideover by default. The slideover button will also most often show if the sidebar is expanded when the app launches:
I guess these are just beta bugs, so let’s not focus on them too much. If a slideover is not the style you want, you can change the navigationSplitViewStyle to .balanced:
struct ContentView: View {
...
var body: some View {
NavigationSplitView {
sidebarContent
} detail: {
detailContent
}.navigationSplitViewStyle(.balanced)
}
}
This will make the sidebar push and resize the main content to the right, instead of sliding in over it:
I really like this style, and it also doesn’t suffer from the disappearing button that I mentioned earlier. The style really depends on your use case, though, so just pick the one you think fits your app best.
Navigation split view selection
Although the sidebar now works, we actually have a pretty serious bug, which you may have noticed in the screenshots above. Although we currently have the .firstPage screen selected, it doesn’t highlight in the sidebar. Also, the NavigationLink items don’t render as buttons, but as plain text.
The reason why this happens is one of the subtle NavigationSplitView requirements that are easy to miss and hat can take a long time to track down. Luckily, it’s easy to fix.
You see, while we do keep track of the current sidebar selection as a @State property and display it by switching over the cases in detailContent, we never bind the selection to the view hierarchy. This means that the navigation split view doesn’t know about the currently selected screen.
To fix this, let’s add a selection parameter to the List that is rendered by the sidebarContent:
var sidebarContent: some View {
List(selection: $selection) {
link(to: .first)
link(to: .second)
link(to: .third)
}
}
If we run the app again, the sidebar will now render the links as buttons, with a selection being applied to the currently selected screen:
Apple probably have their reasons for designing the API this way, but I think it would have been nice if you could specify the selection directly on the NavigationSplitView and have it automatically applying it to the List. The current api makes it easy to overlook that you have to specify it for the list.
Styling the navigation split view on iPad
The navigation split view takes its colors from the .accent color by default, but you can override this by specifying a custom .accentColor:
struct ContentView: View {
...
var body: some View {
NavigationSplitView {
sidebarContent
} detail: {
detailContent
}
.accentColor(.green)
}
}
As you can see below, applying an accent color will affect all content, including the sidebar button, the sidebar list and the detail content buttons:
You can stop the accent color from being used in the detail screen buttons by applying a global tint color:
struct ContentView: View {
...
var body: some View {
NavigationSplitView {
sidebarContent
} detail: {
detailContent
}
.tint(.blue)
.accentColor(.green)
.navigationSplitViewStyle(.balanced)
}
}
However, a tint color affects buttons in more ways than the accent color, by also tinting the background:
A better way is to reset the accent color on the detail content, instead of specifying a global tint color:
struct ContentView: View {
...
var body: some View {
NavigationSplitView {
sidebarContent
} detail: {
detailContent
.accentColor(.accentColor)
}
.accentColor(.green)
.navigationSplitViewStyle(.balanced)
}
}
This will apply a green accent color to the sidebar, but reset the accent color for the detail content:
If you want to use different accent colors for the sidebar toggle button and the sidebar content, you can just apply an separate accent color to the sidebar content:
struct ContentView: View {
...
var body: some View {
NavigationSplitView {
sidebarContent
.accentColor(.purple)
} detail: {
detailContent
.accentColor(.accentColor)
}
.accentColor(.green)
.navigationSplitViewStyle(.balanced)
}
}
This can be useful if your app requires the button and content to be colored differently, which I need in an app that I’m currently working on:
Styling the navigation split view on iPhone
If you run the app on an iPhone, you’ll see how the NavigationSplitView is automatically converted to a NavigationStackView, with the initial selection being pushed by default:
As you can see, our applied accent colors are still being applied here, with the green color being applied to the back button and the standard color being applied to the detail content button.
However, if you now tap “Back” to present the sidebar, you can see that the list is rendered as a plain List instead of using the .sidebar style:
Furthermore, the purple accent color isn’t applied, since the plain list style ignores it. The current selection is also only indicated briefly before being reset.
If you want to color the list items on iPhone, you thus have to use the listRowBackground modifier:
extension ContentView {
...
var sidebarContent: some View {
List(selection: $selection) {
link(to: .first)
link(to: .second)
link(to: .third)
}
.listStyle(.sidebar)
.listRowBackground(Color.purple)
}
...
}
However, while you can apply custom background colors to separate list items, you can’t highlight the currently selected page, since presenting the menu will reset the current selection.
Conclusion
I really like the new NavigationSplitView and think the .balanced style gives me a really nice design in an app that I’m currently porting to iOS 16. There are some strange api choices and some design limitations, but overall I think that this is a great addition to SwiftUI.
Discussions & More
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