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TopAppBar 与操作图标

添加带操作项的标题栏。

TopAppBar 与操作图标 是 CoddyKit 上的免费 Jetpack Compose 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 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。

The Title Bar

The strip across the top with your screen name and actions is the TopAppBar. It gives users a stable anchor that says where they are. 🧭

A Minimal TopAppBar

At its simplest, a TopAppBar just needs a title. Drop it into the Scaffold topBar slot and you have a real Material header.

TopAppBar(
    title = { Text("Inbox") }
)

Title Is a Composable

Notice the title takes a Composable lambda, not a String. That means you can put any content there, though usually a single Text fits best.

The navigationIcon Slot

The leading navigationIcon slot holds your back or menu button. Wrap an Icon in an IconButton so it is tappable and sized correctly.

navigationIcon = {
    IconButton(onClick = { }) {
        Icon(Icons.Default.Menu, "Menu")
    }
}

The actions Slot

Trailing buttons go in the actions slot. It is a RowScope, so each IconButton you add lines up neatly on the right edge.

actions = {
    IconButton(onClick = { }) {
        Icon(Icons.Default.Search, "Search")
    }
}

Always Pass contentDescription

Every Icon in a bar needs a contentDescription. Screen readers announce it, so a Search icon should say Search, not stay silent.

Bar Variants

Material 3 offers CenterAlignedTopAppBar, MediumTopAppBar, and LargeTopAppBar. They differ only in title size and alignment, so pick by feel.

Coloring the Bar

Use TopAppBarDefaults.topAppBarColors to recolor the container and title. Lean on theme colors so the bar stays consistent in light and dark.

colors = TopAppBarDefaults.topAppBarColors(
    containerColor = MaterialTheme.colorScheme.primary
)

Collapsing Bars

Pass a scrollBehavior and connect it to your content's nested scroll to make large bars shrink as the user scrolls down.

Do Not Overcrowd

Keep actions to two or three icons. Move the rest behind an overflow menu so the bar stays readable on small phones.

Wire It to Scaffold

The bar lives in Scaffold's topBar slot, so the content area shrinks automatically and your screen body never hides behind it.

Scaffold(topBar = { TopAppBar(title = { Text("Home") }) }) { p -> }

Quick Check

You add a search IconButton to a TopAppBar. Where does it belong?

Recap

A TopAppBar holds a title, a leading navigationIcon, and trailing actions. Describe every icon, keep it tidy, and place it in the topBar slot. ✨

常见问题解答

「TopAppBar 与操作图标」课时是免费的吗？

是的 — 「TopAppBar 与操作图标」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。

「TopAppBar 与操作图标」这节课中我会学到什么？

添加带操作项的标题栏。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 2 节课，共 4 节。

「TopAppBar 与操作图标」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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