加载、成功与错误用户界面
整洁地呈现每种网络结果。
加载、成功与错误用户界面 是 CoddyKit 上的免费 Jetpack Compose Academy 课时。 这是第 4 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。
Every Request Has Three Outcomes
A network call is either still loading, finished with data, or failed. Great screens show something honest for all three.
Model State With a Sealed Class
A sealed class captures those outcomes as distinct types, so the compiler forces you to handle each case in the UI.
sealed class UiState {
object Loading : UiState()
data class Success(val users: List<User>) : UiState()
data class Error(val message: String) : UiState()
}Start in the Loading State
Initialize your state as Loading so the screen shows a spinner the instant it appears, before any data arrives.
var state by mutableStateOf<UiState>(UiState.Loading)Update on Success
When the call returns, swap the state to Success with the fetched list. Compose recomposes and reveals the content.
state = UiState.Success(api.getUsers())Update on Error
In your catch block, move to the Error state with a friendly message instead of leaving the user stuck on a spinner.
catch (e: Exception) {
state = UiState.Error("Couldn't load users")
}Branch With when
In the Composable, use a when over the state. Each branch renders exactly the right UI for that outcome.
when (val s = state) {
is UiState.Loading -> { }
is UiState.Success -> { }
is UiState.Error -> { }
}Show a Spinner While Loading
For the loading branch, a centered CircularProgressIndicator reassures users that something is happening. ⏳
is UiState.Loading -> CircularProgressIndicator()Render the Data on Success
The success branch reads the list and draws it, usually in a LazyColumn so long results scroll smoothly.
is UiState.Success -> UserList(s.users)Offer a Retry on Error
The error branch should show the message plus a Retry button that re-runs your load function. Failures shouldn't be dead ends.
is UiState.Error -> RetryView(s.message, ::loadUsers)Handle the Empty Case
Success doesn't always mean items. When the list is empty, show a calm empty state rather than a blank screen.
One State Drives the Whole Screen
Because a single state object decides everything, your UI can never show a spinner and data at once. It stays predictable.
Quick Check
Why model loading, success, and error as a sealed class?
Recap: Rendering Every Outcome
You modeled state as a sealed class, branched with when, and showed loading, data, errors, and empties. You can now ship a robust networked screen.
常见问题解答
「加载、成功与错误用户界面」课时是免费的吗？
是的 — 「加载、成功与错误用户界面」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。
「加载、成功与错误用户界面」这节课中我会学到什么？
整洁地呈现每种网络结果。 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 4 节课，共 4 节。
「加载、成功与错误用户界面」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。