How to use AnyLayout in SwiftUI | Bootcamp #70

Summary

在这段视频脚本中，Nick介绍了Swift UI中的“Any Layout”概念。他首先解释了Swift UI视图中常见的VStack和HStack都遵循了布局协议，而Any Layout是一个类型擦除的布局，允许开发者使用任何布局而非特定的垂直或水平堆叠。Nick通过创建一个名为“Any Layout Boot Camp”的Swift UI视图，展示了如何使用水平和垂直尺寸类来根据不同设备的方向调整布局。他演示了在紧凑和常规尺寸类下，如何使用if语句来决定是使用垂直堆叠（VStack）还是水平堆叠（HStack）。最后，他展示了如何使用Any Layout来简化代码，使得布局能够自动适应不同的屏幕尺寸和方向，从而实现更灵活的用户界面设计。

Takeaways

• 📘 Swift UI 中的 `AnyLayout` 是一个布局协议，允许开发者使用任何布局而不仅仅是特定的 `HStack` 或 `VStack`。
• 🔄 `AnyLayout` 是一个类型擦除的布局，意味着它可以代表任何可能的布局类型。
• 📱 设备的方向和屏幕尺寸会影响布局，Swift UI 通过 `horizontalSizeClass` 和 `verticalSizeClass` 来识别这些属性。
• 📊 `horizontalSizeClass` 可以是 `compact` 或 `regular`，这取决于设备在水平方向上的空间大小。
• 📈 `verticalSizeClass` 同样可以是 `compact` 或 `regular`，取决于设备在垂直方向上的空间大小。
• 🔧 开发者可以根据 `horizontalSizeClass` 的值来决定使用 `VStack` 还是 `HStack`，以适应不同的屏幕尺寸和方向。
• 📱 在实际应用中，通过检查 `horizontalSizeClass` 的值，可以动态地在 `VStack` 和 `HStack` 之间切换以优化布局。
• 🌐 通过 `AnyLayout`，可以简化布局代码，使其更加清晰和易于维护。
• 🛠️ 对于初学者来说，了解 `AnyLayout` 和如何根据设备方向和屏幕尺寸调整布局是重要的，但通常不需要过于复杂。
• 🤖 如果应用的布局可以在不同设备上通用而无需调整，那么使用单一布局可能更为合适。
• 🔄 `AnyLayout` 使得布局能够实时自动适应用户的操作，如移动或旋转设备，因为环境变量会实时更新。

Q & A

Swift UI 中的 'AnyLayout' 是什么？

在Swift UI中，'AnyLayout' 是一个协议，它允许创建使用任意布局的视图，而不仅仅是特定的HStack或VStack。它是一个类型擦除的布局，可以简化布局代码的编写。

Swift UI 的布局协议有哪些用途？

Swift UI的布局协议用于定义视图的布局行为。几乎所有的Swift UI视图都以某种形式使用VStack或HStack，这些Stacks都遵循布局协议，使得开发者能够创建和自定义布局。

如何使用Swift UI中的水平和垂直尺寸类来适应不同设备的方向？

通过检查环境变量中的水平和垂直尺寸类，可以判断设备是处于紧凑模式还是常规模式。紧凑模式意味着屏幕空间较小，而常规模式则表示有更多的空间。根据这些信息，开发者可以决定使用VStack或HStack来适应不同的布局需求。

在Swift UI中，如何根据设备的尺寸类动态改变布局？

可以使用Swift UI的条件语句来检查水平尺寸类，如果尺寸类是紧凑的，则使用VStack；如果是常规的，则使用HStack。这样可以使布局根据设备的宽度自动调整。

Swift UI中的 'AnyLayout' 如何帮助简化布局代码？

通过使用 'AnyLayout'，开发者可以将特定的布局（如VStack或HStack）封装进一个类型擦除的布局中，这样就可以在代码中统一处理不同的布局，而不需要重复编写条件逻辑。

为什么在某些情况下，不使用 'AnyLayout' 可能更好？

如果一个单一的布局就能够适应不同的设备和方向，而不需要复杂的适配逻辑，那么直接使用VStack或HStack可能更简单、更清晰。'AnyLayout' 更适用于需要根据设备尺寸类频繁改变布局的场景。

如何在Swift UI中创建一个新的Swift UI视图文件？

在Swift UI的Navigator中，可以右键点击并选择创建一个新的文件，选择Swift UI View，然后给文件命名，例如 'AnyLayoutBootCamp'。

Swift UI中的环境变量是如何实时更新的？

Swift UI中的环境变量，如水平和垂直尺寸类，会根据用户的交互实时更新，例如当用户旋转设备时，这些变量会立即反映出新的方向和尺寸信息。

如何在Swift UI中查看设备的水平和垂直尺寸类？

可以通过在Swift UI视图中使用水平尺寸类和垂直尺寸类的debugDescription属性来查看当前的尺寸类状态。

Swift UI的布局协议和 'AnyLayout' 有什么关系？

布局协议定义了Swift UI中布局的行为，而 'AnyLayout' 是一个实现该协议的类型擦除布局，它允许开发者将任何布局抽象化，从而在代码中统一处理。

在Swift UI中，如何使用 'AnyLayout' 来根据设备的方向改变布局？

通过在 'AnyLayout' 的初始化中使用条件语句，根据水平尺寸类是紧凑还是常规，来决定传递给 'AnyLayout' 的是VStack布局还是HStack布局。

为什么在Swift UI中，即使在横屏模式下，某些设备的尺寸类可能仍然是紧凑的？

这是因为尺寸类的判断不仅基于屏幕的方向，还基于屏幕的实际大小。即使在横屏模式下，如果屏幕的宽度不足以容纳更多的内容，尺寸类可能仍然是紧凑的。

Outlines

00:00

😀 Swift UI 布局协议简介

Nick 老师在视频中介绍了 Swift UI 中的布局协议，特别是 'AnyLayout' 的使用。他提到几乎所有的 Swift UI 视图都包含某种形式的 VStack 或 HStack，这些 Stacks 都遵循布局协议。Swift UI 提供了一种类型擦除的布局叫做 'AnyLayout'，允许开发者使用任意布局而不是特定的 HStack 或 VStack。Nick 老师计划在未来的视频中更深入地探讨布局协议以及如何自定义它。本段视频主要面向初学者，展示了 'AnyLayout' 的基本概念以及如何在应用程序中使用它。

05:03

📱 设备方向与布局适应性

Nick 老师讨论了如何根据设备的方向调整布局。他提到了两个关键的环境变量：水平尺寸类和垂直尺寸类，并解释了它们在不同设备和方向上的表现。例如，iPhone Plus 在竖屏模式下垂直尺寸类是常规的，在横屏模式下则变为紧凑的。Nick 老师强调，作为开发者，应该更多地关注这些环境变量告诉我们的信息，而不是具体的设备类型。他通过一个简单的例子展示了如何根据尺寸类的不同来决定使用 VStack 或 HStack。

10:04

🤓 'AnyLayout' 的实际应用与简化

在讨论了布局适应性之后，Nick 老师引入了 'AnyLayout' 的概念，并展示了如何使用它来简化布局代码。他解释了 'AnyLayout' 是一种类型擦除的布局，可以代表任何可能的布局，如 VStack 或 HStack。通过使用 'AnyLayout'，开发者可以根据水平尺寸类是紧凑还是常规，来决定使用垂直堆栈还是水平堆栈，从而使得布局代码更加简洁。Nick 老师还提到，对于初学者来说，使用 'AnyLayout' 来适应布局变化已经足够，尽管可以创建自定义布局并将其类型擦除为 'AnyLayout'。

Keywords

💡Swift UI

Swift UI 是苹果公司开发的一种用于创建用户界面的框架，它允许开发者使用Swift语言快速构建iOS、iPadOS、macOS、tvOS和watchOS的应用程序界面。在视频中，Swift UI 被用来介绍布局协议和如何使用 `AnyLayout` 来创建适应不同设备和方向的视图。

💡布局协议 (Layout Protocol)

布局协议是Swift UI中的一个核心概念，它定义了如何将视图的子元素进行排列。几乎所有的Swift UI视图都遵循这个协议，如VStack和HStack。视频提到了布局协议，但主要聚焦于介绍 `AnyLayout`。

💡VStack

VStack是Swift UI中的一个视图，代表垂直堆栈，用于垂直排列子视图。在视频中，VStack被用来创建一个垂直排列的文本视图，展示了如何根据设备的方向和大小调整布局。

💡HStack

HStack是Swift UI中的另一个视图，代表水平堆栈，用于水平排列子视图。视频通过HStack展示了如何根据设备的横向尺寸类别（horizontal size class）来改变布局，以适应更多的横向空间。

💡AnyLayout

AnyLayout是Swift UI中的一个类型擦除的布局，允许开发者创建一个可以是任何布局的视图。视频中通过 `AnyLayout` 简化了布局逻辑，使得代码更加简洁，并能够自动适应设备的方向和大小变化。

💡尺寸类别 (Size Class)

尺寸类别是Swift UI中用于描述设备屏幕尺寸和布局环境的概念。视频提到了水平尺寸类别（horizontal size class）和垂直尺寸类别（vertical size class），并解释了它们如何影响布局的选择。

💡类型擦除 (Type Erasure)

类型擦除是一种编程技术，允许将具体类型隐藏起来，只暴露其协议或接口。在视频中，通过 `AnyLayout` 使用了类型擦除，使得具体的布局类型（如VStack或HStack）被隐藏，只通过协议进行交互。

💡设备方向 (Device Orientation)

设备方向指的是用户使用设备时的物理方向，如竖屏（portrait）或横屏（landscape）。视频通过改变模拟器的方向来展示如何根据设备方向变化来调整布局。

💡环境变量 (Environment Variables)

环境变量是Swift UI中用于存储和访问关于设备和环境信息的变量。视频中提到了环境变量，如尺寸类别，它们会实时更新以反映设备状态的变化，从而允许布局自动适应这些变化。

💡条件语句 (Conditional Statements)

条件语句是一种编程结构，用于基于特定条件执行不同的代码分支。在视频中，使用了条件语句（如 `if` 和 `else`）来根据尺寸类别决定使用VStack还是HStack。

💡模拟器 (Simulator)

模拟器是一种软件，可以模拟不同设备的硬件和软件环境，允许开发者在没有实际设备的情况下测试应用程序。视频通过模拟器展示了如何查看和测试不同设备方向和尺寸类别下的布局效果。

Highlights

Nick介绍了Swift UI中的布局协议，几乎所有视图都包含某种形式的VStack或HStack，它们都遵循这个协议。

Swift UI提供了一个类型擦除的布局叫做AnyLayout，允许我们使用任何布局而不是特定的HStack或VStack。

介绍了如何使用AnyLayout来创建视图，并通过Swift UI Boot Camp播放列表进行演示。

讨论了设备方向和布局自适应，包括如何使用水平和垂直尺寸类来调整布局。

通过一个实际的例子，展示了如何在iPhone不同型号和方向下，根据尺寸类调整布局。

解释了在iPhone Plus模型中，肖像模式下垂直尺寸类是常规的，而在风景模式下是紧凑的。

强调了作为开发者，应该更多关注空间大小而不是设备的具体方向。

演示了如何使用HStack和VStack以及如何通过尺寸类来决定使用哪种布局。

展示了在iPhone 14 Pro上，即使在风景模式下，水平尺寸类仍然是紧凑的。

说明了在更大的设备上，如iPhone 14 Pro Max，在风景模式下水平尺寸类是常规的。

介绍了如何使用AnyLayout来简化代码，使其更加清晰地处理不同布局。

通过一个条件语句，展示了如何根据水平尺寸类是紧凑还是常规来决定使用VStack或HStack。

强调了AnyLayout的实用性，它可以实时适应用户的设备方向变化。

提到了对于初学者来说，理解并应用AnyLayout是一个很好的起点，但更复杂的自定义布局可能需要更深入的学习。

Nick建议，如果一个单一的布局可以适应所有情况，那么可能不需要使用AnyLayout。

视频最后，Nick感谢观众观看，并预告了下一期视频的内容。

Transcripts

welcome back everybody my name is Nick

this is swiftel thinking and in this

video we're going to take a very quick

look at any layout in Swift UI this is

basically an introduction to the layout

protocol in Swift UI so when we're

creating Swift UI views almost every

view has some sort of vstack or H stack

all of those Stacks conform to this

layout protocol and Swift UI has a type

erased layout called any layout that

allows us to create views using any any

layout rather than a specific H stack or

a v stack so I'm going to do a video in

the future that gets more into the

actual layout protocol and how we can

really customize it ourselves but in

this video we're going to do a very

beginner level look at what is any

layout and how can I use it in my

application all right welcome back

everybody again in the Swift UI boot

camp playlist it's going to be another

quick video here some of these are

really small features but I just want to

get them on your guys's radar we're

going to right click the Navigator here

create a new file it'll be a swift UI

View and we're going to call this one

any layout boot camp let's click create

let's jump inside real quick this should

be a very fast one here any layout is a

tool that we can use to basically adapt

our layout depending on the device

orientation and let's get into it I

haven't touched on this very much in

this playlist because um if you're a

beginner I guess I don't think it's the

first thing you should be worried about

but in the environment um there's

actually two key paths that we can use

here I'll use the back slash period here

and there is a horizontal size class

let's make this a private variable

called horizontal size class and let's

do another one for the vertical size

class and I'll call this vertical size

class I haven't really touched on these

much in this playlist but the size class

for iPhone is either compact or regular

and it's basically just the size of the

screen that the view is on so if you

just go and Google horizontal size class

on iOS one of the top hits is this blog

we're going to look at real quick from

user loaf.com blogs siiz classes it's a

great little read if you have some extra

time but the bottom line of size glasses

is basically that there is regular and

there's Compact and if we look at this

example here a iPhone plus model

if it is in portrait mode the vertical

size class would be regular and then if

it's in landscape mode the vertical size

class would be compact now this

definitely gets a little confusing

because different models are going to

have different classes for example some

devices might be in landscape mode and

still have a regular height or vice

versa but as a developer I think we

should focus Less on whether or not the

device is in landscape mode and more

just on if if this class if apple is

telling us that the device is compact we

know it's going to have smaller space

and then we can adapt our layout and so

I focus Less on the actual devices here

and more just on the these environment

variables are going to tell us whether

or not it's compact or regular so let's

start this out with a hstack and maybe

have add some spacing of 12 and I'm just

going to put two texts on the screen

let's just put in horizontal with a

colon and let's just put the horizontal

size class dot dis do debug description

for now and I'm just going to do it for

the vertical as well just so that we can

see what these actually are and sorry

let's make this a vstack all right so

right now the

horizontal the horizontal size class is

compact the vertical size class is

regular we can kind of assume that right

like look at this device this the

vertical is the regular it's the full

height light and the horizontal is

compact it's the shorter width of the

device and we're going to and now we're

going to draw some stuff on the screen

here let's make another little vstack

here and let's just put in text

Alpha and I will copy that let's do beta

let's do gamma cool all right so we have

a vstack on the screen and and we're

going to focus just on this tiny vstack

here the alpha beta gamma we're not

going to focus on the horizontal

vertical I'm just going to leave that on

the screen so that we can see

uh the actual values now if this was

your app and you were trying to make a

different layout for whether or not the

device was larger or smaller whether it

was compact or regular you would add

some cod to like if horizontal size

class is equal to and we can see that

it's either going to be regular or

Compact and if it is compact then maybe

we want to put this vstack on the screen

cool and then we'll say else so if it is

not compact right meaning it's regular

the horizontal size class is regular

meaning there's a lot of space

horizontally so right now we can tell

that there's not a lot of space

horizontally and because of that we

probably want to put our code in some

sort of vstack but if it was the regular

Dimension so probably if this device was

in landscape mode we would have a lot of

space and in that case we might want to

put our layout in an

hstack so let's look at a quick example

here so I'm using right now an iPhone 14

pro right and in the Pro if we are in

portrait mode the horizontal is Compact

and if I rotate it I'm going to click

this little icon down here and go to

orientation we're going to go to

landscape we can say even in landscape

on the iPhone 14 pro here the horizontal

is still compact so this is one of those

cases where it's not super intuitive you

would think here we have more room but

this is technically still a compact UI

and so in all my compact uis we're going

to have this vertical stack let's change

this back to Portrait but this time I'm

going to change my simulator so for

example here if I switch my my simulator

to iPhone 14 pro

Max right this is a the Max has a larger

screen size so if I switch this now to

the landscape mode we can see in the

horizontal size class in landscape mode

on the larger device here is now regular

so on the Mac sizes and also on like the

iPads we're going to get the horizontal

size as regular and we can see our code

since it is now regular and not compact

our Alpha Beta gamma is actually in a h

stack which is pretty cool so this would

be a better UI for the larger width of

the device here because I have this

space but on the compact version I want

to keep it in a

vstack so this is cool and we can write

this code but what we're talking about

in this video is just something called

any layout and it's basically being able

to write this a little bit cleaner

because this is cool but if you get

really complex examples like if you had

entire screens inside here and inside

here it might get really maybe tricky to

work with so now what we're going to do

is basically just write this code a

little bit cooler um by using something

called any layout when it comes to the

Swift language uh generally when we see

this word any before something it

implies that it's a type eraser of

something now I haven't covered what

type erasers are in this beginner

playlist and I don't think you really

need to know what they are but it

basically just means that any

layout is something that could be any of

the possible layouts and so in this case

layout is actually a protocol vstack is

a layout and H stack is a layout and

this any layout is just saying we're

going to give it a piece of code that

could be any layout and so the closure

here and the closure here are the exact

same so either of those could work for

any

layout so what we're going to do really

simply we're going to say let layout of

type any layout and we're going to set

it equal to any layout and then you'll

see in here we have to pass in a layout

now if I start typing in vstack you'll

see that v stack layout is the official

layout of the vertical stack so I'll

I'll press enter here vstack layout open

and close parentheses so now this is

actually type any layout but we know

it's actually going to be a vstack

layout and so I can put this on the

screen now with layout and open the

brackets so the same thing that we have

here this vstack with the brackets I'm

going to now just put this code inside

here so now we have any layout and this

will be the content inside that layout

all right and now obviously we want to

still use this this logic here so if the

horizontal size class is compact then we

want the vertical layout otherwise we

want the horizontal layout so I'm just

going to use a tary operator here I'm

going to say let layout of type any

layout set it equal to if the horizontal

size class is equal to compact question

mark then we're going to use a vertical

layout that is erased to any layout

otherwise let's use any layout with an

hstack layout so if the horizontal size

class is compact it should be a v stack

otherwise an H stack I'll zoom out a

little bit just so this is on one line

and now we're just going to comment this

out of our

code we're just going to have layout

here and we're going to look at the

simulator and we can see that the

horizontal size class is regular right

now so it's in an H stack and if I

switch back to the portrait mode

horizontal is Compact and we're in a

vstack that's all we're going to learn

in this video there are ways to make

your own layouts and then you can type

erase your custom layouts to any layout

but generally speaking especially for

beginner apps I think this is basically

the maximum of the logic that you're

going to need you're just taking

whatever the layout is erasing it so

that we can call it once in our code I

think this is super cool it's awesome

that it adapts in real time so if the

user is like moving your app or rotating

your app this layout will adapt

automatically immediately because these

environment variables get updated in

real

time but I just wanted to show you guys

that I don't use this that often if you

can have a single layout that just works

um without having to adapt to the

changing device that's probably better

but if you need to adapt now you know

how that's it for this video thank you

guys for watching as always I am Nick

this is swiftel thinking and I will see

you in the next

[Music]

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