####iOS7 Programming Cookbook 第三章学习笔记 NSLayoutConstraint
#####Autolayout and the Visual Format Language Introduction
#####ViewController.m1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57@interface ViewController ()
@property (nonatomic, strong) UIButton *button1;
@property (nonatomic, strong) UIButton *button2;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//UIButtonTypeRoundedRect：一个圆角矩形样式按钮
//UIButtonTypeSystem：系统风格的按钮,比如导航栏和工具栏所示
self.button1 = [UIButton buttonWithType:UIButtonTypeSystem];
//正常或者默认状态，,但无论是选择还是启用高亮显示。
[self.button1 setTitle:@"Button 1" forState:UIControlStateNormal];
self.button2 = [UIButton buttonWithType:UIButtonTypeSystem];
[self.button2 setTitle:@"Button 2" forState:UIControlStateNormal];
//返回一个布尔值,用于显示视图的autoresizing面具是转化为基于约束的布局的约束系统。
self.button1.translatesAutoresizingMaskIntoConstraints = NO;
self.button2.translatesAutoresizingMaskIntoConstraints = NO;
// self.button1.frame = CGRectMake(0, 0, 50, 50);
self.button1.backgroundColor = [UIColor redColor];
[self.view addSubview:self.button1];
[self.view addSubview:self.button2];
/*
创建约束。view1.attr1 = view2.attr2 *乘数+常量”
如果方程没有第二个视图和属性,使用零和NSLayoutAttributeNotAnAttribute。
*/
//布局约束，限制项：属性：相关：项：属性：乘数：常数：
NSLayoutConstraint *button1CenterYConstraint = [NSLayoutConstraint constraintWithItem:self.button1 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];
NSLayoutConstraint *button2CenterYConstraint = [NSLayoutConstraint constraintWithItem:self.button2 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];
/*
创建约束。view1.attr1 = view2.attr2 *乘数+常量”
如果方程没有第二个视图和属性,使用零和NSLayoutAttributeNotAnAttribute。
*/
NSLayoutConstraint *button1LeftEqualToButton2Right = [NSLayoutConstraint
constraintWithItem:self.button1 attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual
toItem:self.button2 attribute:NSLayoutAttributeRight multiplier:1.0f constant:0.0f];
//setPriority：设置优先级，UILayoutPriorityDefaultLow：这是一个按钮的优先级水平拥抱它的内容 250
[button1LeftEqualToButton2Right setPriority:UILayoutPriorityDefaultLow];
/*
创建约束。view1.attr1 = view2.attr2 *乘数+常量”
如果方程没有第二个视图和属性,使用零和NSLayoutAttributeNotAnAttribute。
*/
NSLayoutConstraint *horizontalDistanceBetweenButtonsConstraint = [NSLayoutConstraint constraintWithItem:self.button1 attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:self.button2 attribute:NSLayoutAttributeLeft multiplier:1.0f constant:200.0f];
//添加约束
[self.view addConstraints:@[button1CenterYConstraint, button2CenterYConstraint, horizontalDistanceBetweenButtonsConstraint, button1LeftEqualToButton2Right]];
}
@end
