共享界面中的状态与重组
使用共享 StateFlow 驱动 Compose
共享界面中的状态与重组 是 CoddyKit 上的免费 Kotlin Multiplatform 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 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。
UI Is a Function of State
In Compose your screen is drawn from state. When the state changes, Compose redraws only the parts that depend on it. You never mutate views by hand.
Recomposition Explained
That automatic redraw is called recomposition. Compose re-runs the affected composables with the new values and updates the screen for you.
Remember Local State
For state owned by a composable, use remember with mutableStateOf so the value survives recomposition instead of resetting every frame.
val count = remember { mutableStateOf(0) }Read and Write State
Wrap the value in by to read and write it like a normal variable. Reading it subscribes the composable, so writing triggers a redraw.
var count by remember { mutableStateOf(0) }
Button(onClick = { count++ }) {
Text("Count: " + count)
}Hoist State Upward
Move state to the lowest common parent and pass values down. This hoisting keeps child composables stateless, reusable and easy to test.
@Composable
fun Counter(value: Int, onInc: () -> Unit) {
Button(onClick = onInc) { Text("" + value) }
}State Lives in Shared Code
Your real source of truth is the shared layer. A cross-platform StateFlow holds screen state once, far from any platform UI framework.
val uiState: StateFlow<ScreenState> = _stateCollect StateFlow in Compose
Bridge that flow into Compose with collectAsState. The composable observes it and recomposes whenever the shared state emits a new value.
val state by viewModel.uiState.collectAsState()
Text(state.title)One Source of Truth
Because state flows from shared code into Compose, Android and iOS render the exact same screen from a single source of truth. No drift.
Avoid Side Effects in Composables
A composable can run many times, so never do work like network calls directly in its body. Keep it a pure description and push effects elsewhere.
LaunchedEffect for Side Work
When you must start a coroutine tied to the UI, use LaunchedEffect. It runs once per key and cancels automatically when the composable leaves.
LaunchedEffect(Unit) {
viewModel.load()
}Derived and Stable State
Compute values from existing state with derivedStateOf so they recalculate only when their inputs change, keeping recomposition cheap.
Quick Check
What keeps a value across recompositions?
Recap: State Drives the UI
You learned that state drives recomposition, how to remember and hoist it, and how shared StateFlow feeds Compose so both apps render one truth. 🔁
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常见问题解答
「共享界面中的状态与重组」课时是免费的吗？
是的 — 「共享界面中的状态与重组」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。
「共享界面中的状态与重组」这节课中我会学到什么？
使用共享 StateFlow 驱动 Compose 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 3 节课，共 4 节。
「共享界面中的状态与重组」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。