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NavController 与 NavHost

定义应用的导航图。

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NavController 与 NavHost 是 CoddyKit 上的免费 Jetpack Compose Academy 课时。这是第 1 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 Jetpack Compose Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Jetpack Compose 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。

Moving Between Screens

Real apps have many screens. Navigation Compose is the official library that lets you move between them without juggling fragments or activities. 🧭

Add the Dependency

Navigation lives in its own artifact. Add androidx.navigation:navigation-compose to your module's build file before you can use any of it.

dependencies {
    implementation("androidx.navigation:navigation-compose:2.7.7")
}

Meet the NavController

The NavController is the brain of navigation. It tracks where you are, remembers history, and carries out every move you ask for.

Remember the Controller

You create one with rememberNavController() so it survives recomposition. Make it once near the top of your app and pass it down.

val navController = rememberNavController()

Meet the NavHost

The NavHost is the container that swaps screens in and out. It shows exactly one destination at a time, based on the controller.

Wire Host to Controller

A NavHost needs two things: the navController that drives it and a startDestination that says which screen to show first.

NavHost(
    navController = navController,
    startDestination = "home"
) { }

The startDestination

The startDestination is the route shown when the app opens. It is also the screen users land on after the back stack empties.

Declaring Destinations

Inside the NavHost lambda you list your screens with composable("route"). Each one ties a route name to the UI it should show.

NavHost(navController, startDestination = "home") {
    composable("home") { HomeScreen() }
    composable("profile") { ProfileScreen() }
}

Navigate by Route

To change screens, call navController.navigate("route"). The host sees the request and swaps in the matching destination instantly.

Button(onClick = { navController.navigate("profile") }) {
    Text("Open profile")
}

One Controller, One Host

Keep a single NavController paired with a single NavHost for an app's main flow. Sharing one source of truth avoids confusing, out-of-sync history.

Why Routes Are Strings

Routes are just String identifiers, like tiny URLs inside your app. This keeps destinations decoupled and easy to link later.

Quick Check

Which piece actually performs the screen change?

在交互式课程中回答

Recap

You met the duo behind navigation: the NavController drives moves and history, while the NavHost shows one destination at a time from your route list. 🎉

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常见问题解答

「NavController 与 NavHost」课时是免费的吗？

是的 — 「NavController 与 NavHost」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 Jetpack Compose Academy 课程的其余内容，请升级到 CoddyKit PRO。 Jetpack Compose Academy 课程共包含 4 节课。

「NavController 与 NavHost」这节课中我会学到什么？

定义应用的导航图。你通过在浏览器中直接运行的动手代码来练习 Jetpack Compose 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 Jetpack Compose Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Jetpack Compose 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 1 节课，共 4 节。

「NavController 与 NavHost」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 Jetpack Compose Academy 课中编写并运行代码吗？

能。每节 Jetpack Compose 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。

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