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有状态与无状态 Composable

将逻辑与展示分离。

有状态与无状态 Composable 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。

Two Kinds of Composables

Every Composable is either stateful (it holds its own data) or stateless (it just renders what you pass in). Knowing which is which shapes your whole app.

What Stateful Means

A stateful Composable remembers something across recompositions, usually with remember. It owns and changes its own data.

fun Counter() {
  var count by remember { mutableStateOf(0) }
  Button(onClick = { count++ }) { Text("Count: " + count) }
}

What Stateless Means

A stateless Composable holds no state of its own. It only reads its parameters and draws, so the same inputs always give the same output. 🎯

fun CounterDisplay(count: Int) {
  Text("Count: " + count)
}

Why Stateless Wins

Stateless Composables are easier to reuse: they fit any screen, in any state, because the caller decides what to show.

Easier to Preview

Because a stateless Composable just takes parameters, you can feed it sample data in @Preview and see every variation instantly.

@Preview
fun PreviewDisplay() {
  CounterDisplay(count = 42)
}

Easier to Test

Stateless parts are predictable: pass an input, assert the output. No hidden internal data means far simpler tests. ✅

The Trade-Off

Stateful Composables are convenient for quick demos, but they trap data inside. That makes them hard to share, preview, or control from outside.

Spotting the Difference

See a remember or mutableStateOf inside? It is stateful. See only parameters being read? It is stateless.

Separate Logic from Looks

A clean pattern: keep one thin stateful wrapper that owns data, and a stateless Composable that only handles how things look.

Composing the Two

The stateful wrapper feeds its data into the stateless one. Now the visual part stays pure while the state lives in just one place.

fun CounterScreen() {
  var count by remember { mutableStateOf(0) }
  CounterDisplay(count = count)
}

A Mindset for Reuse

Default to stateless when you build components. Add state only at the spot that truly needs to own it, and no lower.

Quick Check

Which kind of Composable is the easiest to reuse and preview?

Recap

Stateful Composables own data; stateless ones just render parameters. Favor stateless components and keep state in one small wrapper. 🚀

常见问题解答

「有状态与无状态 Composable」课时是免费的吗？

是的 — 「有状态与无状态 Composable」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。

「有状态与无状态 Composable」这节课中我会学到什么？

将逻辑与展示分离。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。

「有状态与无状态 Composable」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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