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Button 与 onClick

在用户点击时运行代码。

Button 与 onClick 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。

Tap, Then React

A button is your app's simplest conversation: the user taps, your code runs. In Compose you express this with the Button composable. 👆

The Button Composable

A Button needs two things: an onClick action and some content to show, usually a Text label inside its trailing lambda.

Button(onClick = { /* do work */ }) {
    Text("Tap me")
}

onClick Runs on Tap

The onClick lambda runs once each time the button is pressed. Put any plain Kotlin code you want there, like updating a value.

Button(onClick = { count = count + 1 }) {
    Text("Add one")
}

Content Is a Lambda

Everything between the button's braces is its content. You are not limited to text; any composable can live inside that slot.

Button(onClick = { send() }) {
    Text("Send now")
}

Wire Up Real State

onClick really shines with state: change a value there and the UI redraws to match the new value automatically.

var liked by remember { mutableStateOf(false) }
Button(onClick = { liked = !liked }) {
    Text(if (liked) "Liked" else "Like")
}

Call a Function

For tidy code, point onClick at a named function instead of inlining logic. Your UI stays readable and the logic stays testable.

Button(onClick = ::saveProfile) {
    Text("Save")
}

Buttons Look Filled by Default

A plain Button renders as a filled, high-emphasis button: solid background, contrasting label. It signals the main action on a screen.

One Primary Action

Reserve the filled Button for the single most important action, like Submit or Continue. Too many filled buttons compete for attention.

Empty onClick Does Nothing

An empty onClick lambda compiles fine and the button still ripples, but nothing happens. Always wire it to real behavior. 🤔

Button(onClick = { }) {
    Text("Does nothing yet")
}

Pass a Modifier

Like most composables, Button accepts a modifier so you can size, pad, or space it within its parent layout.

Button(
    onClick = { go() },
    modifier = Modifier.fillMaxWidth()
) { Text("Continue") }

Tap to Confirm

Think of onClick as the moment of commitment: the user has decided. Use it to save, navigate, or trigger the work they asked for.

Quick Check

You wrote a Button but tapping it does nothing.

Recap: Tap Into Action

You met the Button composable: an onClick lambda for behavior plus a content lambda for its label. Tap, run code, update state. 🎉

常见问题解答

「Button 与 onClick」课时是免费的吗？

是的 — 「Button 与 onClick」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。

「Button 与 onClick」这节课中我会学到什么？

在用户点击时运行代码。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。

「Button 与 onClick」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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