使用 xib 创建可重用的 UIView(并从故事板加载) [英] Creating a reusable UIView with xib (and loading from storyboard)

问题描述

好的，StackOverflow 上有很多关于这个的帖子，但没有一个特别清楚解决方案.我想创建一个带有随附的 xib 文件的自定义 UIView.要求是:

OK, there are dozens of posts on StackOverflow about this, but none are particularly clear on the solution. I'd like to create a custom UIView with an accompanying xib file. The requirements are:

• 没有单独的UIViewController——一个完全独立的类
• 类中的插座允许我设置/获取视图的属性

我目前的做法是:

1. 覆盖-(id)initWithFrame:

-(id)initWithFrame:(CGRect)frame {
    self = [[[NSBundle mainBundle] loadNibNamed:NSStringFromClass([self class])
                                          owner:self
                                        options:nil] objectAtIndex:0];
    self.frame = frame;
    return self;
}

在我的视图控制器中使用 -(id)initWithFrame: 以编程方式实例化

MyCustomView *myCustomView = [[MyCustomView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
[self.view insertSubview:myCustomView atIndex:0];

这很好用(尽管从不调用 [super init] 并且简单地使用加载的笔尖的内容设置对象似乎有点可疑 – 这里有关于 在这种情况下添加一个子视图，它也可以正常工作).但是，我也希望能够从情节提要中实例化视图.所以我可以:

This works fine (although never calling [super init] and simply setting the object using the contents of the loaded nib seems a bit suspect – there is advice here to add a subview in this case which also works fine). However, I'd like to be able to instantiate the view from the storyboard also. So I can:

1. 在故事板的父视图上放置一个 UIView
2. 将其自定义类设置为 MyCustomView

3. 覆盖-(id)initWithCoder:——我见过的最常见的代码符合如下模式:

1. Place a UIView on a parent view in the storyboard
2. Set its custom class to MyCustomView

3. Override -(id)initWithCoder: – the code I've seen the most often fits a pattern such as the following:

-(id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self initializeSubviews];
    }
    return self;
}

-(id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self initializeSubviews];
    }
    return self;
}

-(void)initializeSubviews {
    typeof(view) view = [[[NSBundle mainBundle]
                         loadNibNamed:NSStringFromClass([self class])
                                owner:self
                              options:nil] objectAtIndex:0];
    [self addSubview:view];
}

当然，这行不通，因为无论我是使用上面的方法，还是以编程方式实例化，最终都会在输入 - 时递归调用 -(id)initWithCoder:(void)initializeSubviews 并从文件中加载笔尖.

Of course, this doesn't work, as whether I use the approach above, or whether I instantiate programatically, both end up recursively calling -(id)initWithCoder: upon entering -(void)initializeSubviews and loading the nib from file.

其他几个 SO 问题与此有关，例如 这里，这里，此处 和此处.但是，给出的答案都不能令人满意地解决问题:

Several other SO questions deal with this such as here, here, here and here. However, none of the answers given satisfactorily fixes the problem:

• 一个常见的建议似乎是将整个类嵌入到 UIViewController 中，并在那里加载笔尖，但这对我来说似乎并不理想，因为它需要添加另一个文件作为包装器

任何人都可以就如何解决这个问题提供建议，并在自定义 UIView 中获得工作插座，而无需大惊小怪/没有瘦控制器包装器?或者有没有替代的、更简洁的使用最少的样板代码做事的方法?

Could anyone give advice on how to resolve this problem, and get working outlets in a custom UIView with minimum fuss/no thin controller wrapper? Or is there an alternative, cleaner way of doing things with minimum boilerplate code?

推荐答案

您的问题是从 initWithCoder:(的后代)调用 loadNibNamed:.loadNibNamed: 在内部调用 initWithCoder:.如果您想覆盖故事板编码器，并始终加载您的 xib 实现，我建议使用以下技术.向您的视图类添加一个属性，并在 xib 文件中将其设置为预定值(在用户定义的运行时属性中).现在，在调用 [super initWithCoder:aDecoder]; 后检查属性的值.如果是预定值，则不调用[self initializeSubviews];.

Your problem is calling loadNibNamed: from (a descendant of) initWithCoder:. loadNibNamed: internally calls initWithCoder:. If you want to override the storyboard coder, and always load your xib implementation, I suggest the following technique. Add a property to your view class, and in the xib file, set it to a predetermined value (in User Defined Runtime Attributes). Now, after calling [super initWithCoder:aDecoder]; check the value of the property. If it is the predetermined value, do not call [self initializeSubviews];.

所以，像这样:

-(instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];

    if (self && self._xibProperty != 666)
    {
        //We are in the storyboard code path. Initialize from the xib.
        self = [self initializeSubviews];

        //Here, you can load properties that you wish to expose to the user to set in a storyboard; e.g.:
        //self.backgroundColor = [aDecoder decodeObjectOfClass:[UIColor class] forKey:@"backgroundColor"];
    }

    return self;
}

-(instancetype)initializeSubviews {
    id view =   [[[NSBundle mainBundle] loadNibNamed:NSStringFromClass([self class]) owner:self options:nil] firstObject];

    return view;
}

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