自动布局和约束问题
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【中文标题】自动布局和约束问题【英文标题】：Issue with autoLayout and constraints 【发布时间】：2013-11-15 10:02:46 【问题描述】：我遇到了 ios 和 AutoLayout 的问题...这是一个测试应用程序，我在其中复制了问题。它包含一个简单的视图控制器，包含一个固定的UIButton；当用户单击此按钮时，委托必须创建一个自定义视图，对其应用定位约束；然后视图有一个方法来构建他的内容视图，并且子视图也被放置了约束。
代码如下：
//MyViewController.m
@implementation MyViewController
- (void)viewDidLoad
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UIButton *start_but = [[UIButton alloc] initWithFrame:CGRectMake(10, 10, 100, 40)];
[start_but setTitle:@"Draw" forState:UIControlStateNormal];
[start_but setTitleColor:[UIColor yellowColor] forState:UIControlStateNormal];
[start_but addTarget:self action:@selector(clickAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:start_but];
- (void)didReceiveMemoryWarning
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
- (void)clickAction: (id)sender
localView = [[MyView alloc] initWithFrame:CGRectMake(0, 0, 400, 300)];
UIView *superview = (UIView*)localView;
superview.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:localView];
NSLayoutConstraint *constr = [NSLayoutConstraint constraintWithItem:localView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:100.0];
[self.view addConstraint:constr];
constr = [NSLayoutConstraint constraintWithItem:localView
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeRight
multiplier:1.0
constant:-50.0];
[self.view addConstraint:constr];
[localView CreateGuiInterface];
@end
//MyView.m
@implementation MyView
- (id)initWithFrame:(CGRect)frame
self = [super initWithFrame:frame];
if (self)
// Initialization code
return self;
-(void)CreateGuiInterface
UIView *superview = self;
self.backgroundColor = [UIColor redColor];
UIButton *but1 = [[UIButton alloc] init];
[but1 setTitle:@"Button" forState:UIControlStateNormal];
[but1 setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
but1.backgroundColor = [UIColor yellowColor];
but1.translatesAutoresizingMaskIntoConstraints = NO;
[superview addSubview:but1];
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:but1
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeRight multiplier:1.0
constant:-20.0];
[superview addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:but1
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:50.0];
[superview addConstraint:constraint];
UILabel *label = [[UILabel alloc] init];
label.text = @"Label";
label.backgroundColor = [UIColor greenColor];
label.textColor = [UIColor blackColor];
label.translatesAutoresizingMaskIntoConstraints = NO;
[superview addSubview:label];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:but1
attribute:NSLayoutAttributeLeft
multiplier:1.0
constant:-40.0];
[superview addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:but1
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:20.0];
[superview addConstraint:constraint];
@end
所以，问题是当我单击 iOS 时似乎无法绘制视图背景颜色。这很奇怪，因为如果我不使用superview.translatesAutoresizingMaskIntoConstraints = NO 并将视图放在固定位置（例如initWithFrame:CGRect(100,200,300,400)）而不使用约束，它工作正常：在子视图和父视图中使用约束会出现问题? AppleDoc 表示约束不能通过视图屏障；所以我用面向本地视图的约束编写了我的应用程序......
有人可以帮助我吗？
感谢您的建议
【问题讨论】：
【参考方案1】：使用 autoLayout 的目的是永远不必在任何视图上设置框架。如果您想以编程方式将您的视图放置在您的超级视图中，您将为此提供约束。我所做的更改您将看到预期的红色背景。我没有更改您的 MyView 实现（只需添加 -(void)CreateGuiInterface; 在 MyView.h 中）。我为演示所做的更改在您的 MyViewController 实现中。
尝试使用以下代码代替您的 viewController：
@interface MyViewController ()
@property (nonatomic, strong) MyView* localView;
@end
@implementation MyViewController
- (void)viewDidLoad
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UIButton *start_but = [[UIButton alloc] init];
start_but.translatesAutoresizingMaskIntoConstraints = NO;
[start_but setTitle:@"Draw" forState:UIControlStateNormal];
[start_but setTitleColor:[UIColor yellowColor] forState:UIControlStateNormal];
[start_but addTarget:self action:@selector(clickAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:start_but];
// The following constraints simply place the initial start button in the top left
NSDictionary* views = NSDictionaryOfVariableBindings(start_but);
NSString* format = @"H:|-[start_but]";
NSArray* constraints = [NSLayoutConstraint constraintsWithVisualFormat:format
options:0
metrics:nil
views:views];
[self.view addConstraints:constraints];
format = @"V:|-[start_but]";
constraints = [NSLayoutConstraint constraintsWithVisualFormat:format
options:0
metrics:nil
views:views];
[self.view addConstraints:constraints];
- (void)clickAction: (id)sender
self.localView = [[MyView alloc] init];
UIView *superview = (UIView*)self.localView;
superview.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:self.localView];
// Here I'm placing your parent view (MyView) 50 points on right of the superview with
// a width of 400 points
NSDictionary* views = NSDictionaryOfVariableBindings(superview);
NSString* format = @"H:[superview(==400)]-(50)-|";
NSArray* constraints = [NSLayoutConstraint constraintsWithVisualFormat:format
options:0
metrics:nil
views:views];
[self.view addConstraints:constraints];
// Vertically 100 points from the top of the superview with a height of 300 points
format = @"V:|-(100)-[superview(==300)]";
constraints = [NSLayoutConstraint constraintsWithVisualFormat:format
options:0
metrics:nil
views:views];
[self.view addConstraints:constraints];
[self.localView CreateGuiInterface];
@end
【讨论】：
是的，你在写，它有效，非常感谢。所以，问题是我曾经用 initWithFrame 设置框架大小......将视图大小设置为约束解决了我的问题。再次感谢！以上是关于自动布局和约束问题的主要内容，如果未能解决你的问题，请参考以下文章