Kotlin Multiplatform Academy · 课时

用于共享界面状态的 StateFlow

公开两个应用都可以收集的可观察状态

用于共享界面状态的 StateFlow 是 CoddyKit 上的免费 Kotlin Multiplatform Academy 课时。这是第 2 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 Kotlin Multiplatform Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Kotlin Multiplatform 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。

State Needs a Holder

UI state is not a one-off stream, it is a value that always exists right now. StateFlow is a Flow that holds a single current value for the screen.

Always Has a Value

Unlike a plain Flow, a StateFlow is hot and always carries a value. A new collector instantly receives the latest state, never an empty start.

MutableStateFlow to Write

You create state with MutableStateFlow, passing the initial value. This is the writable side your shared logic updates over time.

private val _count = MutableStateFlow(0)

Expose a Read-Only View

Keep the mutable field private and expose it as a read-only StateFlow. The UI can observe but never reach in and mutate it directly.

val count: StateFlow<Int> = _count.asStateFlow()

Update with .value

Write new state by setting .value on the mutable flow. Every collector is notified of the change right away.

_count.value = _count.value + 1

Atomic update {}

For safe read-then-write changes, prefer the update function. It computes the next value from the current one without race conditions.

_count.update { current -> current + 1 }

Reads Are Distinct

StateFlow only emits when the value actually changes. Setting the same value again is ignored, so the UI is not woken up for nothing.

A Single Source of Truth

Put your screen state in one StateFlow and both apps read from it. That makes your shared logic the single source of truth for the screen. ✨

Model the Whole Screen

Often the value is a data class describing the entire screen. One UiState object means the UI reads everything it needs from a single place.

data class UiState(
    val loading: Boolean = false,
    val items: List<String> = emptyList()
)

Collect Gets the Latest

When a screen starts collecting, it immediately gets the current state, then every update after. No flicker, no missing first render.

StateFlow vs Flow

Use a plain Flow for events that come and go, and a StateFlow for state that always has a current value. UI almost always wants StateFlow.

Quick Check

One key idea to lock in.

Recap

You used StateFlow as a single source of truth: a hot stream that always holds the screen's current value, ready for both apps to observe. ✨

常见问题解答

「用于共享界面状态的 StateFlow」课时是免费的吗？

是的 — 「用于共享界面状态的 StateFlow」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 Kotlin Multiplatform Academy 课程的其余内容，请升级到 CoddyKit PRO。 Kotlin Multiplatform Academy 课程共包含 4 节课。

「用于共享界面状态的 StateFlow」这节课中我会学到什么？

公开两个应用都可以收集的可观察状态你通过在浏览器中直接运行的动手代码来练习 Kotlin Multiplatform 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 Kotlin Multiplatform Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Kotlin Multiplatform 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 2 节课，共 4 节。

「用于共享界面状态的 StateFlow」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 Kotlin Multiplatform Academy 课中编写并运行代码吗？

能。每节 Kotlin Multiplatform 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

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