代码约束

 1 #import "RootViewController.h"
 2 
 3 @interface RootViewController ()
 4 
 5 @end
 6 
 7 @implementation RootViewController
 8 
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11     // Do any additional setup after loading the view.
12     
13 #pragma mark - label的约束
14     // 如果想通过约束来控制视图的位置大小，不需要设置frame
15     UILabel *label = [[UILabel alloc] init];
16     
17     // 禁止自动转换
18     label.translatesAutoresizingMaskIntoConstraints = NO;
19     
20     label.backgroundColor = [UIColor redColor];
21     
22     // 视图添加到父视图上之后，才能进行布局
23     [self.view addSubview:label];
24     
25     
26     // 进行约束布局
27     // 距离上面50
28     /*
29      constraintWithItem:要约束的视图对象
30      第一个attribute:要约束视图对象的属性
31      relatedBy:和参照视图的关系
32      toItem:参照视图的对象
33      第二个attribute:参照视图对象的属性
34      multiplier:比例
35      constant:距离的数值
36      */
37     [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:50]];
38     
39     // 距离左边100
40     [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1 constant:100]];
41     
42     // 距离右边100
43     [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeRight multiplier:1 constant:-100]];
44     
45     // 距离底部500
46     [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeBottom multiplier:1 constant:-500]];
47 
48 #pragma mark - label1的约束
49     
50     UILabel *label1 = [[UILabel alloc] init];
51     label1.translatesAutoresizingMaskIntoConstraints = NO;
52     label1.backgroundColor = [UIColor greenColor];
53     [self.view addSubview:label1];
54     
55     
56     // 布局label1
57     [self.view addConstraints:@[
58                                 // 距离上边50
59                                 [NSLayoutConstraint constraintWithItem:label1 attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:label attribute:NSLayoutAttributeBottom multiplier:1 constant:50],
60                                 
61                                 // 和label左边对齐
62                                 [NSLayoutConstraint constraintWithItem:label1 attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:label attribute:NSLayoutAttributeLeading multiplier:1 constant:0],
63                                 
64                                 // 和label右边对齐
65                                 [NSLayoutConstraint constraintWithItem:label1 attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:label attribute:NSLayoutAttributeTrailing multiplier:1 constant:0],
66                                 
67                                 // 高度60
68                                 [NSLayoutConstraint constraintWithItem:label1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:60]
69                                 
70                                 ]];
71     
72 }
73 
74 @end

 

转载于:https://www.cnblogs.com/zhizunbao/p/5447436.html