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items 与 itemsIndexed

渲染数据行集合。

items 与 itemsIndexed 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。

From Data to Rows

Your data usually lives in a list, like a List of strings or objects. The items block turns each element into a row on screen.

The items Function

Call items with your collection and a lambda. Compose runs the lambda for each element it needs to show.

LazyColumn {
    items(fruits) { fruit ->
        Text(fruit)
    }
}

The Element Parameter

The lambda receives one element at a time. Name it clearly, like fruit or user, then build UI from that single value.

items(users) { user ->
    Text(user.name)
}

Build a Whole Row

The lambda can hold any layout, not just Text. Wrap several composables in a Row to make a richer list item.

items(users) { user ->
    Row { Text(user.name); Text(user.age.toString()) }
}

When You Need the Position

Sometimes you want the row's index, like showing a rank number or alternating colors. Plain items doesn't give you that.

Meet itemsIndexed

Use itemsIndexed when you need the position. Its lambda receives both the index and the element together.

itemsIndexed(songs) { index, song ->
    Text("$index: $song")
}

Index Comes First

Order matters: in itemsIndexed the index is the first parameter and the element is the second. Swapping them is a common slip.

itemsIndexed(tasks) { i, task ->
    Text("Step ${i + 1}: $task")
}

Numbering Made Easy

Index starts at zero, so add one for human-friendly numbering. This makes ranked or step-by-step lists feel natural.

Add a Single Fixed Row

Need one standalone row, like a header or footer? Use item (singular) for a single piece of content among your items blocks.

LazyColumn {
    item { Text("My List") }
    items(data) { Text(it) }
}

Mix and Match Freely

Inside one LazyColumn you can combine several item and items calls. They render in the order you declare them.

Pick the Right Tool

Reach for items when the element is enough, and itemsIndexed when you also need each row's position. That's the whole choice.

Quick Check

Pick the right builder for the job.

Recap: items and itemsIndexed

Use items to map data to rows, itemsIndexed when you need the position, and item for a single fixed row. Mix them freely. 🎯

常见问题解答

「items 与 itemsIndexed」课时是免费的吗？

是的 — 「items 与 itemsIndexed」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。

「items 与 itemsIndexed」这节课中我会学到什么？

渲染数据行集合。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。

「items 与 itemsIndexed」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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