SwiftUI Academy · 课时

选中标签绑定

在代码中跟踪并更改当前标签。

选中标签绑定 是 CoddyKit 上的免费 SwiftUI Academy 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 SwiftUI Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 SwiftUI Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Knowing the Active Tab

Sometimes your code needs to know or change which tab is showing. For that you bind the selection to your own state. 🎯

Give Each Tab a Tag

First mark each tab with a unique tag value so SwiftUI can identify which one is selected.

HomeScreen()
    .tabItem { Label("Home", systemImage: "house") }
    .tag(0)

Store the Selection

Add a @State property to hold the current tab tag. Its value tells you which tab is active.

@State private var selectedTab = 0

Bind selection to TabView

Pass that state to the TabView selection parameter using a dollar sign to create a two-way binding.

TabView(selection: $selectedTab) {
    // tabs with .tag(...)
}

Tags Must Match

The tag type and the selection type must match. If tags are Int, selectedTab must be an Int too.

Reading Which Tab Is Open

Once bound, selectedTab updates whenever the user taps. You can read it anywhere to react to the current tab.

Switching Tabs in Code

Change the state value and the UI follows. Setting selectedTab jumps the user to that tab programmatically.

selectedTab = 1

A Jump-to-Tab Button

A button can switch tabs by writing to the binding, handy for a "Go to Settings" shortcut deep in your app.

Button("Open Settings") {
    selectedTab = 1
}

Enums Make Tags Safer

Plain numbers are easy to mix up. A enum of named cases makes each tag readable and mistake-proof.

enum Tab { case home, settings }

Re-Tapping the Selected Tab

Tapping the active tab again keeps the same selection. You can watch for this to scroll a list back to the top.

When You Need the Binding

Skip the binding if tabs are fully independent. Add it only when code must read or set the active tab.

Quick Check

Let us check how SwiftUI tracks the active tab.

Recap: Selected Tab Binding

Tag each tab and bind a @State value to selection, and you can both read the active tab and switch tabs from code. 🎉

常见问题解答

「选中标签绑定」课时是免费的吗？

是的 — 「选中标签绑定」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 SwiftUI Academy 课程的其余内容，请升级到 CoddyKit PRO。 SwiftUI Academy 课程共包含 4 节课。

「选中标签绑定」这节课中我会学到什么？

在代码中跟踪并更改当前标签。你通过在浏览器中直接运行的动手代码来练习 SwiftUI Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 SwiftUI Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 SwiftUI Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「选中标签绑定」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 SwiftUI Academy 课中编写并运行代码吗？

能。每节 SwiftUI Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

← 返回 SwiftUI Academy