实时预览画布
使用 Xcode 预览即时查看界面变化。
实时预览画布 是 CoddyKit 上的免费 SwiftUI 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 SwiftUI Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 SwiftUI 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。
Meet the Canvas
Beside your code, Xcode shows a canvas that renders your view live. You see your UI without ever building and launching the full app. 👀
Show or Hide It
If the canvas is missing, open the Editor menu and turn on Canvas. It appears on the right, next to your Swift code.
The #Preview Block
A small #Preview block at the bottom of the file tells the canvas what to render. The template adds one for ContentView automatically.
#Preview {
ContentView()
}Live Updates
Change your code and the canvas refreshes almost instantly. This live update loop is what makes SwiftUI feel fast and playful. ⚡
Try an Edit
Edit the Text view's wording and watch the canvas change as you type. Seeing results immediately makes experimenting safe and fun.
Text("Hello, SwiftUI!")Resume the Preview
Sometimes the canvas pauses and shows a Resume button. Click it to restart the preview after a change it could not apply live.
Interactive Mode
The play-style live mode lets you tap and scroll right in the canvas. You can test buttons and gestures without a simulator.
Preview Devices
You can point a preview at a specific device, like an iPhone SE. This helps you check how your layout looks on smaller screens.
Multiple Previews
Add more than one #Preview block to compare states side by side, such as light mode next to dark mode at the same time.
Previews Are Not Shipped
Preview code is for development only. It never ships to users, so feel free to fill previews with fake sample data.
Faster Than Building
The canvas is far quicker than a full build. Use it as your main loop while designing, and reach for the simulator only for deeper testing.
Quick Check
Which block in your file tells the canvas what to render?
Recap
The canvas renders your view live via a #Preview block, updating as you type. It is your fastest way to design and iterate. 🎨
常见问题解答
「实时预览画布」课时是免费的吗？
是的 — 「实时预览画布」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 SwiftUI Academy 课程的其余内容，请升级到 CoddyKit PRO。 SwiftUI Academy 课程共包含 4 节课。
「实时预览画布」这节课中我会学到什么？
使用 Xcode 预览即时查看界面变化。 你通过在浏览器中直接运行的动手代码来练习 SwiftUI 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 SwiftUI Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 SwiftUI 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。
「实时预览画布」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 SwiftUI Academy 课中编写并运行代码吗？
能。每节 SwiftUI 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。