苹果API翻译之UIView（一）

霉霉镇楼

每个iOS新版本的发布，苹果都会对API进行更新，作者总是会忽略这方便的学习。另外，很多知识点独立的都有涉及，但是并没有形成系统的知识体系。作者拟通过这样的方式，督促自己的学习，以及做到对知识点的总结。

说明：英文为原文，斜体字为中文翻译（机翻+个人理解），粗体是作者根据自己的经验补充的说明，数字小标是作者认为需要另开文章研究的知识点。

UIView

An object that manages the content for a rectangular area on the screen.
一个管理屏幕上矩形区域的内容的对象。

Overview

Views are the fundamental building blocks of your app's user interface, and the UIView class defines the behaviors that are common to all views. A view object renders content within its bounds rectangle and handles any interactions with that content.The UIView class is a concrete class that you can instantiate and use to display a fixed background color. You can also subclass it to draw more sophisticated content. To display labels, images, buttons, and other interface elements commonly found in apps, use the view subclasses provided by the UIKit framework rather than trying to define your own.

视图是应用程序用户界面的基本构建块，UIView类定义了所有视图通用的行为。视图对象在其边界矩形内呈现内容，并处理与该内容的任何交互。UIView类是一个具体的类，您可以实例化并使用它来显示固定的背景颜色。您也可以将其子类化以绘制更复杂的内容。要显示应用程序中常见的标签，图像，按钮和其他界面元素，请使用UIKit框架提供的视图子类，而不是尝试定义自己的。

Because view objects are the main way your application interacts with the user, they have a number of responsibilities. Here are just a few:

因为视图对象是您的应用程序与用户交互的主要方式，所以他们有很多职责。这里仅仅呈现它的部分作用：

• Drawing and animation

  • Views draw content in their rectangular area using UIKit or Core Graphics.
  • Some view properties can be animated to new values.

• Layout and subview management

  • Views may contain zero or more subviews.
  • Views can adjust the size and position of their subviews.
  • Use Auto Layout to define the rules for resizing and repositioning your views in response to changes in the view hierarchy.

• Event handling

  • A view is a subclass of UIResponder and can respond to touches and other types of events.
  • Views can install gesture recognizers to handle common gestures.

• 绘图和动画

  • 视图使用UIKit或Core Graphics在其矩形区域中绘制内容。（作者说一句：每个 UIView 内部都有一个 CALayer 在背后提供内容的绘制和显示，并且 UIView 的尺寸样式都由内部的 Layer 所提供。扩展阅读：详解 CALayer 和 UIView 的区别和联系）
  • 某些视图属性可以以动画的形式呈现值的改变。

• 布局和子视图管理

  • 视图可能包含零个或多个子视图。
  • 视图可以调整其子视图的大小和位置。
  • 使用自动布局来定义调整视图的大小和重新定位的规则，以响应视图层次结构中的更改。

• 事件处理

  • 视图是UIResponder触摸和其他类型的事件的子类并可以响应。
  • 视图可以添加手势识别器来处理常见的手势。（作者说一句：UIView和CALayer的主要区别就是前者可以响应手势）

Views can be nested inside other views to create view hierarchies, which offer a convenient way to organize related content. Nesting a view creates a parent-child relationship between the child view being nested (known as the subview) and the parent (known as the superview). A parent view may contain any number of subviews but each subview has only one superview. By default, when a subview’s visible area extends outside of the bounds of its superview, no clipping of the subview's content occurs. Use the clipsToBounds property to change that behavior.

视图可以嵌套在其他视图中以创建视图层次结构，这提供了组织相关内容的便捷方式。嵌套视图会在嵌套的子视图（称为子视图）和父级（称为超级视图）之间创建父子关系。父视图可以包含任意数量的子视图，但每个子视图只有一个超级视图。默认情况下，当子视图的可见区域扩展到其超级视图的边界之外时，不会发生剪辑子视图的内容。使用clipsToBounds来更改该行为。 （作者说一句：clipsToBounds常用在给UIImageView添加图片时，图标的尺寸大于控件尺寸时。）

The geometry of each view is defined by its frame and bounds properties. The frame property defines the origin and dimensions of the view in the coordinate system of its superview. The bounds property defines the internal dimensions of the view as it sees them and is used almost exclusively in custom drawing code. The center property provides a convenient way to reposition a view without changing its frame or bounds properties directly.

每个视图的尺寸由其frame和bounds属性定义。frame属性定义视图的初始位置和它在父视图坐标系中的尺寸。bounds属性定义视图的内部尺寸。center属性提供了一种方便的方式来重新定位视图，而不直接改变其视图frame或bounds属性。

For detailed information about how to use the UIView class, see View Programming Guide for iOS.

有关如何使用UIView该类的详细信息，请参阅查看iOS编程指南。

Creating a View

Normally, you create views in your storyboards by dragging them from the library to your canvas. You can also create views programmatically. When creating a view, you typically specify its initial size and position relative to its future superview. For example, the following example creates a view and places its top-left corner at the point (10, 10) in the superview's coordinate system (once it is added to that superview).

通常，您可以通过将图形拖放到画布中，从而在故事板中创建视图。您也可以以编程方式创建视图。创建视图时，您通常会指定其相对于其未来超级视图的初始大小和位置。例如，以下示例创建一个视图，并将其左上角放置在超级视图坐标系中的点（10,10）（一旦添加到该超级视图中）。

CGRect  viewRect = CGRectMake(10, 10, 100, 100);
UIView* myView = [[UIView alloc] initWithFrame:viewRect];

To add a subview to another view, call the addSubview: method on the superview. You may add any number of subviews to a view, and sibling views may overlap each other without any issues in iOS. Each call to the addSubview: method places the new view on top of all other siblings. You can specify the relative z-order of subview by adding it using the insertSubview:aboveSubview: and insertSubview:belowSubview: methods. You can also exchange the position of already added subviews using the exchangeSubviewAtIndex:withSubviewAtIndex: method.

要将子视图添加到另一个视图，请调用superview上的方法addSubview:。您可以将任意数量的子视图添加到视图中，并且子视图可能在iOS中相互重叠，没有任何问题。每次调用addSubview:方法将新视图放在所有其他子视图之上。您可以通过使用insertSubview:aboveSubview:和方法insertSubview:belowSubview:添加子视图来指定子视图的相对次序。您还可以使用该方法exchangeSubviewAtIndex:withSubviewAtIndex:交换已添加的子视图的位置。

After creating a view, create Auto Layout rules to govern how the size and position of the view change in response to changes in the rest of the view hierarchy. For more information, see Auto Layout Guide.

创建视图后，创建自动布局规则以管理视图的大小和位置如何更改以响应视图层次结构的其余部分中的更改。有关详细信息，请参阅自动布局指南。

The View Drawing Cycle

View drawing occurs on an as-needed basis. When a view is first shown, or when all or part of it becomes visible due to layout changes, the system asks the view to draw its contents. For views that contain custom content using UIKit or Core Graphics, the system calls the view’s drawRect: method. Your implementation of this method is responsible for drawing the view’s content into the current graphics context, which is set up by the system automatically prior to calling this method. This creates a static visual representation of your view’s content that can then be displayed on the screen.

视图绘制根据需要进行。当首次显示视图时，或者由于布局更改而使其全部或部分变得可见时，系统会要求视图绘制其内容。对于包含使用UIKit或Core Graphics的自定义内容的视图，系统调用该视图的drawRect:方法。您执行此方法负责将视图的内容绘制到当前图形上下文中，此方法的调用时之前由系统自动设置的。这将使你可以创建视图内容，并在之后显示在屏幕。

作者说一句：在实际开发中，当我们需要在一个View上通过上下文绘制视图时，可以将绘制视图的代码写在drawRect:中，因为在drawRect:中会自动创建上下文，我们只需要实现剩下的绘制代码即可。大致代码如下：

- (void)drawRect:(CGRect)rect{  
    CGContextRef context = UIGraphicsGetCurrentContext();  
    ...
}

When the actual content of your view changes, it is your responsibility to notify the system that your view needs to be redrawn. You do this by calling your view’s setNeedsDisplay or setNeedsDisplayInRect: method of the view. These methods let the system know that it should update the view during the next drawing cycle. Because it waits until the next drawing cycle to update the view, you can call these methods on multiple views to update them at the same time.

当您的视图的实际内容发生变化时，您有责任通知系统您的视图需要重新绘制。您可以通过调用setNeedsDisplay或视图的方法setNeedsDisplayInRect:来执行此操作。这些方法让系统知道它应该在下一个绘图循环中更新视图。因为它等待直到下一个绘图周期来更新视图，您可以在多个视图上调用这些方法来同时更新它们。

Note
If you are using OpenGL ES to do your drawing, you should use the GLKView class instead of subclassing UIView. For more information about how to draw using OpenGL ES, see OpenGL ES Programming Guide.

注意
如果您使用OpenGL ES来完成绘图，则应该使用GLKView该类而不是子类化UIView。有关如何使用OpenGL ES绘制的更多信息，请参阅OpenGL ES编程指南。

For detailed information about the view drawing cycle and the role your views have in this cycle, see View Programming Guide for iOS.

有关视图绘制周期的详细信息以及您的视图在此周期中的角色，请参阅查看iOS编程指南。

Animations

Changes to several view properties can be animated—that is, changing the property creates an animation starting at the current value and ending at the new value that you specify. The following properties of the UIView class are animatable:

对这几个视图属性的更改可以拥有动画效果，也就是说，更改属性将创建一个从当前值开始的动画，并以您指定的新值结束。UIView该类的以下属性是可动画的：

• frame
• bounds
• center
• transform
• alpha
• backgroundColor

To animate your changes, create a UIViewPropertyAnimator object and use its handler block to change the values of your view's properties. The UIViewPropertyAnimator class lets you specify the duration and timing of your animations, but it performs the actual animations. You can pause a property-based animator that is currently running to interrupt the animation and drive it interactively. For more information, see UIViewPropertyAnimator.

要更改动画，请创建一个UIViewPropertyAnimator对象并使用其代码块来更改视图属性的值。该UIViewPropertyAnimator类让您指定动画的持续时间和时机，并且会执行实际的动画。您可以暂停当前运行的基于属性的动画，同时您可以中断动画并以交互方式重新启动动画。有关更多信息，请参阅UIViewPropertyAnimator

作者说一句：UIViewPropertyAnimator是iOS10新添加的属性，它与以前实现动画的不同之处在于，我们可以暂停和重启动画。简单的说其可以更细腻的制作和控制动画。扩展阅读：如何使用iOS 10的UIViewPropertyAnimator做动画

Threading Considerations

Manipulations to your application’s user interface must occur on the main thread. Thus, you should always call the methods of the UIView class from code running in the main thread of your application. The only time this may not be strictly necessary is when creating the view object itself, but all other manipulations should occur on the main thread.

对应用程序的用户界面的操作必须发生在主线程上。因此，您应该始终从应用程序主线程中调用UIView类的方法。唯一可能不是严格必要的是创建视图对象本身，但所有其他操作都应该发生在主线程上。

Subclassing Notes

The UIView class is a key subclassing point for visual content that also requires user interactions. Although there are many good reasons to subclass UIView, it is recommended that you do so only when the basic UIView class or the standard system views do not provide the capabilities that you need. Subclassing requires more work on your part to implement the view and to tune its performance.

UIView类是一个呈现视觉内容和用户交互的关键类。尽管有很多很好的理由使UIView子类化，但建议您只有在基本UIView类或标准系统视图不提供所需功能的情况下才能这样做。子类需要更多的工作来实现视图并调整其性能。

For information about ways to avoid subclassing, see Alternatives to Subclassing.

有关避免子类化的方法的信息，请参阅子类的替代方法。

Methods to Override

When subclassing UIView, there are only a handful of methods you should override and many methods that you might override depending on your needs. Because UIView is a highly configurable class, there are also many ways to implement sophisticated view behaviors without overriding custom methods, which are discussed in the Alternatives to Subclassing section. In the meantime, the following list includes the methods you might consider overriding in your UIView subclasses:

当进行UIView子类化时，只有少数方法应该被重写，还有许多可以根据需要重写的方法。因为UIView是一个高度可配置的类，还有许多方法来实现复杂的视图行为，而不会重写自定义方法，这在子类的替代方法部分中有所讨论。同时，以下列表包括您可能会考虑重写在您的UIView子类中的方法：

• Initialization:

  • initWithFrame: - It is recommended that you implement this method. You can also implement custom initialization methods in addition to, or instead of, this method.
  • initWithCoder: - Implement this method if you load your view from storyboards or nib files and your view requires custom initialization.
  • layerClass Use this property only if you want your view to use a different Core Animation layer for its backing store. For example, if your view uses tiling to display a large scrollable area, you might want to set the property to the CATiledLayer class.

• 初始化：

  • initWithFrame: - 建议您实现此方法。您还可以实现自定义初始化方法，除此之外，也可以替代该方法。（作者说一句：注意，只有UIView及其子类拥有此构造方法，UIViewContoller是不存在此构造方法的哟）
  • initWithCoder: - 如果从storyboard或nib文件加载视图，并且您的视图需要自定义初始化，请执行此方法。
  • layerClass仅当您希望视图为其后备存储使用不同的Core Animation图层时，才能使用此属性。例如，如果您的视图使用平铺来显示大的可滚动区域，则可能需要将属性设置为CATiledLayer类。（作者有话说：每一个UIView都是寄宿在一个CALayer的示例上。这个图层是由视图自动创建和管理的，那我们可以用别的图层类型替代它么？一旦被创建，我们就无法代替这个图层了。但是如果我们继承了UIView，那我们就可以重写+layerClass方法使得在创建的时候能返回一个不同的图层子类。UIView会在初始化的时候调用+layerClass方法，然后用它的返回类型来创建宿主图层。官方解释: default is [CALayer class]. Used when creating the underlying layer for the view. 对于这个方法，作者确实没有用到过，留一个坑，之后会做研究。）

作者挖坑：为什么从nib加载视图时，是调用的这个序列化构造方法？从nib创建view的过程跟序列号，反序列化有什么关系？^[1]

作者挖坑：为什么在swift中即使用代码实现UIView子类的构造方法，也需要实现required init?(coder aDecoder: NSCoder)方法？^[2]

• Drawing and printing:

  • drawRect: - Implement this method if your view draws custom content. If your view does not do any custom drawing, avoid overriding this method.
  • drawRect:forViewPrintFormatter: - Implement this method only if you want to draw your view’s content differently during printing.

• 绘图和印刷：

  • drawRect: - 如果您的视图绘制自定义内容，请执行此方法。如果您的视图不执行任何自定义绘图，请避免覆盖此方法。（作者说一句：上面已经提过drawRect的常用场景了，跟这里的解释差不多。）
  • drawRect:forViewPrintFormatter: - 仅当您要在打印期间绘制视图的内容时，才能实现此方法。（作者说一句：UIViewPrintFormatter在网上看了一下，指的是打印格式，如果输出的内容需要打印出来，才会使用到这个方法。什么是打印格式？请点我）

• Layout and Constraints:

  • requiresConstraintBasedLayout Use this property if your view class requires constraints to work properly.
  • updateConstraints - Implement this method if your view needs to create custom constraints between your subviews.
  • alignmentRectForFrame:, frameForAlignmentRect: - Implement these methods to override how your views are aligned to other views.
  • didAddSubview:, willRemoveSubview: - Implement these methods as needed to track the additions and removals of subviews.
  • willMoveToSuperview:, didMoveToSuperview - Implement these methods as needed to track the movement of the current view in your view hierarchy.

• 布局和约束：

  • requiresConstraintBasedLayout 如果您的视图类需要约束才能正常工作，请使用此属性。
  • updateConstraints - 如果您的视图需要在您的子视图之间创建自定义约束，请执行此方法。
  • alignmentRectForFrame:, frameForAlignmentRect:- 实现这些方法来覆盖视图与其他视图的对齐方式。
  • didAddSubview:，willRemoveSubview:- 根据需要实施这些方法来跟踪子视图的添加和删除。
  • willMoveToSuperview:，didMoveToSuperview- 根据需要实现这些方法来跟踪视图层次结构中当前视图的移动。

  作者挖坑：有关布局方法的使用介绍，会在以后的Masonry专题里面进行研究和说明 ^[3]

• Event Handling:

  • gestureRecognizerShouldBegin: - Implement this method if your view handles touch events directly and might want to prevent attached gesture recognizers from triggering additional actions.
  • touchesBegan:withEvent:, touchesMoved:withEvent:, touchesEnded:withEvent:, touchesCancelled:withEvent: - Implement these methods if you need to handle touch events directly. (For gesture-based input, use gesture recognizers.)

• 事件处理：

  • gestureRecognizerShouldBegin: - 如果您的视图直接处理触摸事件，并且可能希望防止附加的手势识别器触发其他操作，请执行此方法。
  • touchesBegan:withEvent:，touchesMoved:withEvent:，touchesEnded:withEvent:，touchesCancelled:withEvent: -如果你需要直接处理触摸事件实现这些方法。（对于基于手势的输入，使用手势识别器。）

作者挖坑：简单的说，就是在手势冲突时，用来判断执行哪个手势操作的代理方法。比如ScrollView上的子控件拥有一个滑动手势，子控件实现gestureRecognizerShouldBegin代理方法，当在这个子控件上滑动时，可以在代理方法中进行判断若：return YES ，该手势会被拦截(不会传递给 ScrollView 进行滚动)。若：return NO， 该手势会传递下去(传递给 ScrollView 进行滚动)。更多关于手势的操作，咱们也挖一个坑，以后补上。^[4]

Alternatives to Subclassing

Many view behaviors can be configured without the need for subclassing. Before you start overriding methods, consider whether modifying the following properties or behaviors would provide the behavior you need.

许多视图行为可以在不需要子类化的情况下进行配置。在开始重写方法之前，请考虑修改以下属性或行为是否会提供所需的行为

• addConstraint: - Define automatic layout behavior for the view and its subviews.

• autoresizingMask - Provides automatic layout behavior when the superview’s frame changes. These behaviors can be combined with constraints.

• contentMode - Provides layout behavior for the view’s content, as opposed to the frame of the view. This property also affects how the content is scaled to fit the view and whether it is cached or redrawn.

• hidden or alpha - Change the transparency of the view as a whole rather than hiding or applying alpha to your view’s rendered content.

• backgroundColor - Set the view’s color rather than drawing that color yourself.

• Subviews - Rather than draw your content using a drawRect: method, embed image and label subviews with the content you want to present.

• Gesture recognizers - Rather than subclass to intercept and handle touch events yourself, you can use gesture recognizers to send an Target-Action to a target object.

• Animations - Use the built-in animation support rather than trying to animate changes yourself. The animation support provided by Core Animation is fast and easy to use.

• Image-based backgrounds - For views that display relatively static content, consider using a UIImageView object with gesture recognizers instead of subclassing and drawing the image yourself. Alternatively, you can also use a generic UIView object and assign your image as the content of the view’s CALayer object.

• addConstraint: -为视图及其子视图定义自动布局行为。

• autoresizingMask -在父视图的框架更改时提供自动布局行为。这些行为可以与约束相结合。

• contentMode -为视图的内容提供布局行为，而不是视图的框架。此属性还影响内容如何缩放以适合视图以及是否缓存或重绘。

• hidden或者alpha -改变整个视图的透明度，而不是隐藏或者将Alpha应用到视图的渲染内容。

• backgroundColor -设置视图的颜色，而不是自己绘制该颜色。

• 使用UIView的子视图而不是使用drawRect:方法绘制您的内容，嵌入图像和标签子视图与您要呈现的内容。

• 手势识别器 -您可以使用手势识别器向目标对象发送Target-Action，而不是子类自己截取和处理触摸事件。

• 动画 -使用内置的动画支持，而不是试图自己动画变化。Core Animation提供的动画支持快速且易于使用。

• 基于图像的背景 -对于显示相对静态内容的视图，考虑使用带有手势识别器的UIImageView对象，而不是自己创建子类并绘制图像。或者，您也可以使用通用UIView对象，并将图像指定为视图CALayer对象的内容。

（作者说一句：简单的说，就是苹果给你提供了有关布局，绘制，动画，手势相关的API，你能用最好就直接用，别总是想着自己造轮子了。）

Animations are another way to make visible changes to a view without requiring you to subclass and implement complex drawing code. Many properties of the UIView class are animatable, which means changes to those properties can trigger system-generated animations. Starting animations requires as little as one line of code to indicate that any changes that follow should be animated. For more information about animation support for views, see Animations.

动画是另一种对视图进行可视化更改的方法，无需您继承和实现复杂的绘图代码。UIView类的许多属性都是可动画效果呈现的，这意味着对这些属性的更改可以触发系统生成的动画。开始动画只需要一行代码就可以表明任何后续的变化都应该是动画的。有关动画支持视图的更多信息，请参阅Animations。

Topics

Creat a View Objcet

• -initWithFrame:

  Initializes and returns a newly allocated view object with the specified frame rectangle.
  初始化并返回具有指定框架矩形的新分配的视图对象。

• -initWithCoder:

  （作者说一句：当使用代码创建UIView或其子类时，调用-initWithFrame:方法，当通过xib创建时，调用-initWithCoder:方法）

--

Configuring a View’s Visual Appearance

• backgroundColor

  The view’s background color.
  视图的背景颜色。

• hidden

  A Boolean value that determines whether the view is hidden.
  一个布尔值，用于确定视图是否被隐藏。

• alpha

  The view’s alpha value.
  视图的alpha值。

• opaque

  A Boolean value that determines whether the view is opaque.
  一个布尔值，用于确定视图是否不透明。

  （作者说一句：hidden，alpha，opaque区别的扩展阅读：UIView中hidden、alpha、clear color与opaque的区别）

• tintColor

  The first nondefault tint color value in the view’s hierarchy, ascending from and starting with the view itself.
  视图层次结构中的第一个非默认色调颜色值，从视图本身和视点开始算起。

• tintAdjustmentMode

  The first non-default tint adjustment mode value in the view’s hierarchy, ascending from and starting with the view itself.
  视图层次结构中的第一个非默认色调调整模式值，从视图本身开始并从视点开始。

  （作者说一句：tintColor完全可以作为一种主题色修改的方案来使用，关于tintColor的扩展阅读：详解 UIView 的 Tint Color 属性）

• clipsToBounds

  A Boolean value that determines whether subviews are confined to the bounds of the view.
  一个布尔值，确定子视图是否被限制在视图的边界。

• clearsContextBeforeDrawing

  A Boolean value that determines whether the view’s bounds should be automatically cleared before drawing.
  一个布尔值，用于确定在绘制之前是否应该自动清除视图边界。

  （作者说一句：决定在视图重画之前是否先清理视图以前的内容，默认值为YES,如果你把这个属性设为NO，那么你要保证能在 drawRect：方法中正确的绘画。如果你的代码已经做了大量优化，那么设为NO可以提高性能，尤其是在滚动时可能只需要重新绘画视图的一部分）

• maskView

  An optional view whose alpha channel is used to mask a view’s content.
  其alpha通道用于屏蔽视图内容的可选视图。

  （作者说一句：还是layer的一个属性。扩展阅读：使用maskView设计动画及遮盖）

• layerClass

  Returns the class used to create the layer for instances of this class.
  返回用于为此类的实例创建图层的类。

• layer

  The view’s Core Animation layer used for rendering.
  视图用于渲染的Core Animation层。

--

Configuring the Event-Related Behavior

• userInteractionEnabled

  A Boolean value that determines whether user events are ignored and removed from the event queue.
  一个布尔值，用于确定用户事件是否被忽略并从事件队列中删除。

• multipleTouchEnabled

  A Boolean value that indicates whether the view receives more than one touch at a time.
  一个布尔值，指示视图是否一次接收多个触摸。

• exclusiveTouch

  A Boolean value that indicates whether the receiver handles touch events exclusively.
  （作者又有话说：1、点击事件之间是可以“同时”共存，并能分别“同时”响应的。（同时点击两个响应区域分别响应）2、线程被阻塞时，点击手势也是可以缓存的，并在线程通畅后统一响应。（单个响应区域的重复点击并重复响应）。）

作者挖坑：关于exclusiveTouch的研究报告 ^[5]

--

Configuring the Bounds and Frame Rectangles

• frame

  The frame rectangle, which describes the view’s location and size in its superview’s coordinate system.
  框架矩形，在其父视图的坐标系中描述视图的位置和大小

• bounds

  The bounds rectangle, which describes the view’s location and size in its own coordinate system.
  边界矩形，它在自己的坐标系统中描述视图的位置和大小。

• center

  The center point of the view's frame rectangle.
  视图的框架矩形的中心点。

• transform

  Specifies the transform applied to the view, relative to the center of its bounds.
  指定应用于视图的变换，相对于其边界的中心

  作者挖坑：修改transform和修改frame的区别 ^[5]

--

Managing the View Hierarchy

• superview

  The receiver’s superview, or nil if it has none.
  接收者的父视图，可能返回nil。

• subviews

  The receiver’s immediate subviews.
  接收者的子视图。

• window

  The receiver’s window object, or nil if it has none.
  接收者的window对象，如果它没有返回nil。

• - addSubview:

  Adds a view to the end of the receiver’s list of subviews.
  将视图添加到接收者的子视图列表的末尾。

• - bringSubviewToFront:

  Moves the specified subview so that it appears on top of its siblings.
  移动指定的子视图，使其出现在其所有子视图之上。v

• - sendSubviewToBack:

  Moves the specified subview so that it appears behind its siblings
  移动指定的子视图，使其出现在所有子视图的后面。

• - removeFromSuperview

  Unlinks the view from its superview and its window, and removes it from the responder chain.
  将视图从其父视图和其窗口中取消链接，并将其从响应者链中移除。

• - insertSubview:atIndex:

  Inserts a subview at the specified index.
  在指定的索引处插入子视图。

• - insertSubview:aboveSubview:

  Inserts a view above another view in the view hierarchy.
  在视图层次结构中的另一个视图上插入一个视图。

• - insertSubview:belowSubview:

  Inserts a view below another view in the view hierarchy.
  在视图层次结构中的另一个视图下插入一个视图。

• - exchangeSubviewAtIndex:withSubviewAtIndex:

  Exchanges the subviews at the specified indices.
  在指定的索引交换子视图。

• - isDescendantOfView:

  Returns a Boolean value indicating whether the receiver is a subview of a given view or identical to that view.
  返回一个布尔值，指示接收者是给定视图的子视图还是与该视图相同层级。

后话

这是API翻译的第一期。我发现在学习的过程中，又会不断引出新的知识点，这些知识点并不是一两句能说得清的，就比如我在下面留的坑。我的想法是，利用每个周末输出一篇API翻译的文章，然后工作日再将文章中的坑补齐。尽量做到有文字，有DEMO的形式。先这么决定吧，喜欢文章的朋友，请关注我的公众号SwiftCoder,如果有幸转载，也请保留公众号的名称。另外有建议的朋友，也请留言。您的鼓励是我坚持的动力。（真正开始写文章，才明白这句话的分量）

如果你喜欢我的文章请关注我的公众号SwiftCoder，我会编写高质量的原创iOS开发内容。

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1. 留坑: xib文件的初始化与initWithCoder的关系 ↩

2. 留坑: 为什么必须调用required init?(coder aDecoder: NSCoder)？ ↩

3. 留坑: Masonry详解 ↩

4. 留坑: 手势操作 ↩

5. 留坑：修改transform和修改frame的区别 ↩ ↩