1 -(void)fun1{
2 //注意使用VFL，不用设置视图的frame
3 UIView *view = [[UIView alloc] init];
4 view.backgroundColor = [UIColor brownColor];
5 [self.view addSubview:view];
6
7 view.translatesAutoresizingMaskIntoConstraints = NO;//注意，要想使约束条件起作用，必须将此属性设置为no
8
9 /*
10 VFL相关的标识符
11 H:代表水平方向
12 V:代表垂直方向
13 |代表父视图
14 - 代表距离 例（H:|-20-）表示距离父视图左侧20像素
15 []代表子视图相关属性
16 */
17
18 //对子视图View进行约束设置，format表示要设置的约束语句，在本句中意思为：view距离父视图左侧30像素，距离父视图右侧20像素（如果没设置具体的数字，且写了-）
19 //options代表对其方式，默认写0就行
20 //metrics 这里是一个字典，当在format中使用了动态数据比如上现这句:@"H:|-[button(==width)]-|",表示这个button的宽度为width,那么这个参数去哪里找呢？就是在这个字典里面找到key对应的值，如果没有找到这个值，app会crash
21 //views 代表约束条件中所涉及的所有视图（父视图除外）
22 NSArray *arr = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-30-[view]-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view)];
23 /*这里用到了一个系统宏定义,NSDictionaryOfVariableBindings(),其作用是生成一个词典,key的名字和对象的标识符相同,以上述为例,生成的词典形式就是{"self.view":self.view,@"_view3":_view3,...},这个词典应当包含需要自动布局的父视图和所有的子视图,
24 */
25 NSArray *arr1 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[view]-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view)];
26
27 [self.view addConstraints:arr];
28 [self.view addConstraints:arr1];
29
30 }
31
32 -(void)fun2{
33 UIView *view = [[UIView alloc] init];
34 view.backgroundColor = [UIColor grayColor];
35 [self.view addSubview:view];
36
37 view.translatesAutoresizingMaskIntoConstraints = NO;
38 //[view(>=200)] 表示给view设置尺寸，此时小括号里的关系运算符只能是 == <= >=，注意，改尺寸的值不要与约束冲突，==：约束可以不写，简写成H:[view(==200)] >=：当左右距离只设置了一个或者都未设置，视图的尺寸为最小值，如果两个都设置时，view 的尺寸为屏幕宽度减去左右距离，此时要保证减后的值>=尺寸最小值
39
40 NSArray *arr = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[view(>=200)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view)];
41
42 NSArray *arr1 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[view(==100)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view)];
43 [self.view addConstraints:arr1];
44 [self.view addConstraints:arr];
45
46 }
47
48 -(void)fun3{
49 UIView *view = [[UIView alloc] init];
50 view.backgroundColor = [UIColor grayColor];
51 [self.view addSubview:view];
52
53 view.translatesAutoresizingMaskIntoConstraints = NO;
54
55 CGFloat width = 200;
56
57 //当我们在设置约束条件时，距离父视图上下左右的像素值以及view的尺寸不是固定的数字(用某个字符串代替)，这时我们需要给metrics设置一个字典，该字典的key必须是约束语句中使用的字符串，对应的value可以自行设置
58 NSArray *arr = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-left-[view(==width)]" options:0 metrics:@{@"width":[NSNumber numberWithFloat:width],@"left":@30} views:NSDictionaryOfVariableBindings(view)];
59
60 NSArray *arr1 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[view(==100)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view)];
61 [self.view addConstraints:arr1];
62 [self.view addConstraints:arr];
63
64 }
65
66 -(void)fun4{
67 UIView *view = [[UIView alloc] init];
68 view.backgroundColor = [UIColor grayColor];
69 [self.view addSubview:view];
70
71 view.translatesAutoresizingMaskIntoConstraints = NO;
72
73 CGFloat width = 200;
74
75 //当我们在设置约束条件时，距离父视图上下左右的像素值以及view的尺寸不是固定的数字(用某个字符串代替)，这时我们需要给metrics设置一个字典，该字典的key必须是约束语句中使用的字符串，对应的value可以自行设置
76 NSArray *arr = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-left-[view(==width)]" options:0 metrics:@{@"width":[NSNumber numberWithFloat:width],@"left":@30} views:NSDictionaryOfVariableBindings(view)];
77
78 NSArray *arr1 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[view(==100)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view)];
79 [self.view addConstraints:arr1];
80 [self.view addConstraints:arr];
81
82
83 UIView *view1 = [[UIView alloc] init];
84 view1.backgroundColor = [UIColor purpleColor];
85 [self.view addSubview:view1];
86
87 view1.translatesAutoresizingMaskIntoConstraints = NO;
88
89 //[view1(view)] 代表view1和view某个方向尺寸相同
90 NSArray *arr2 = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[view1(view)]-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view1,view)];
91
92 //V:[view]-[view1]-20-|：子视图view1垂直方向距离平级子视图view 8像素（默认）
93 NSArray *arr3 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[view]-[view1]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(view,view1)];
94 [self.view addConstraints:arr2];
95 [self.view addConstraints:arr3];
96
97
98 }
99
100 //用VFL实现label自适应
101 -(void)fun5{
102 UILabel *label = [[UILabel alloc] init];
103 label.backgroundColor = [UIColor grayColor];
104 label.numberOfLines = 0;
105 label.lineBreakMode = NSLineBreakByCharWrapping;
106 label.text = @"hiwehfdiuwehdiowqhdoiwehjdoiuwehdiouwhediuwheioudhewiuodhwehoihiuhiuhiuhiluhiuhiuhiuhihuhuuhhuh";
107 [self.view addSubview:label];
108 label.translatesAutoresizingMaskIntoConstraints = NO;
109
110 NSArray *arr = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[label]-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(label)];
111
112 NSArray *arr1 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[label]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(label)];
113
114 [self.view addConstraints:arr];
115 [self.view addConstraints:arr1];
116 }