凡添加topLayoutGuide约束code [英] Where to add topLayoutGuide constraint code

问题描述

解决方案

想出一个解决方案，把我的子类导航控制器的 viewDidLoad中方法如下code .m文件：

   - （无效）viewDidLoad中{
    [超级viewDidLoad中];
    //在载入视图后的任何额外的设置。    如果（[[[的UIDevice currentDevice] systemVersion]的floatValue]≥= 7.0f）{
        [自拍] setTranslatesAutoresizingMaskIntoConstraints：NO];        ID topGuide = [个体经营topLayoutGuide]
        UIView的* selfView = [自拍]
        *的NSDictionary = viewsDictionary NSDictionaryOfVariableBindings（selfView，topGuide）;
        [[[自拍]窗口] addConstraints：
         [NSLayoutConstraint constraintsWithVisualFormat：@V：[topGuide] -0- [selfView]
                                             选项​​：0
                                             指标：无
                                               观点：viewsDictionary]
        ];
        [[[自拍]窗口] layoutSubviews] //你必须在这里调用此方法或系统会引发异常
    }
}
 

原贴

苹果公司<一href=\"https://developer.apple.com/LIBRARY/IOS/documentation/UIKit/Reference/UIViewController_Class/Reference/Reference.html#//apple_ref/occ/instp/UIViewController/topLayoutGuide\"相对=nofollow>商务部没有说清楚，在哪里（哪一类，哪一种方法），我应该把code的这个块（不知道是什么做自指的是在code）：

  [按钮setTranslatesAutoresizingMaskIntoConstraints：NO];
ID topGuide = myViewController.topLayoutGuide;
*的NSDictionary = viewsDictionary NSDictionaryOfVariableBindings（按钮，topGuide）;
[myViewController.view addConstraints：
    [NSLayoutConstraint constraintsWithVisualFormat：@V：[topGuide] -20- [按钮]
                                                 选项​​：0
                                                 指标：无
                                                   观点：viewsDictionary]
self.view layoutSubviews; //你必须在这里调用此方法或系统会引发异常
];
 

我觉得，code以上块有一些错字，所以这里就是我认为它应该是：

  [按钮setTranslatesAutoresizingMaskIntoConstraints：NO];
ID topGuide = myViewController.topLayoutGuide;
*的NSDictionary = viewsDictionary NSDictionaryOfVariableBindings（按钮，topGuide）;
[myViewController.view addConstraints：
    [NSLayoutConstraint constraintsWithVisualFormat：@V：[topGuide] -20- [按钮]
                                                 选项​​：0
                                                 指标：无
                                                   观点：viewsDictionary]
];
self.view.layoutSubviews; //你必须在这里调用此方法或系统会引发异常
 

解决方案

在这种情况下，自可引用视图控制器。有了这个code，你添加约束其观点，因此可以布局它的子视图，你叫 layoutSubviews 时设置。如果您在 viewDidLoad中方法添加此code（我推荐你增加它那里），你可以替换 myViewController 按自

Solution

Figured out a solution, put the following code in the viewDidLoad method of my subclassed navigation controller .m file:

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0f) {
        [[self view] setTranslatesAutoresizingMaskIntoConstraints:NO];

        id topGuide = [self topLayoutGuide];
        UIView * selfView = [self view];
        NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings (selfView, topGuide);
        [[[self view] window] addConstraints:
         [NSLayoutConstraint constraintsWithVisualFormat:@"V:[topGuide]-0-[selfView]"
                                             options:0
                                             metrics:nil
                                               views:viewsDictionary]
        ];
        [[[self view] window] layoutSubviews]; // You must call this method here or the system raises an exception
    }
}

Original Post

Apple's doc didn't say it clear that where (which class, which method) should I put this chunk of code (don't know what does self refers to in the code):

[button setTranslatesAutoresizingMaskIntoConstraints: NO];
id topGuide = myViewController.topLayoutGuide;
NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings (button, topGuide);
[myViewController.view addConstraints:
    [NSLayoutConstraint constraintsWithVisualFormat: @"V: [topGuide]-20-[button]"
                                                 options: 0
                                                 metrics: nil
                                                   views: viewsDictionary]
self.view layoutSubviews; // You must call this method here or the system raises an exception
];

And I feel that the above chunk of code has some typo, so here's what I think it should be:

[button setTranslatesAutoresizingMaskIntoConstraints: NO];
id topGuide = myViewController.topLayoutGuide;
NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings (button, topGuide);
[myViewController.view addConstraints:
    [NSLayoutConstraint constraintsWithVisualFormat: @"V: [topGuide]-20-[button]"
                                                 options: 0
                                                 metrics: nil
                                                   views: viewsDictionary]
];
self.view.layoutSubviews; // You must call this method here or the system raises an exception

解决方案

In that case, self can refer to a view controller. With this code, your are adding constraint to its view, so it can layout it subviews as you set them when calling layoutSubviews. If you add this code in the viewDidLoad method (and I recommand you to add it there) you can replace occurrences of myViewController by self

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