AutoLayout自動布局,NSLayoutConstraint 視圖約束使用,autolayout布局
一.方法
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:<#(id)#> attribute:<#(NSLayoutAttribute)#> relatedBy:<#(NSLayoutRelation)#> toItem:<#(id)#> attribute:<#(NSLayoutAttribute)#> multiplier:<#(CGFloat)#> constant:<#(CGFloat)#>]
Item:要約束的控制項
attribute:要約束的控制項約束的類型(做怎樣的約束)
relatedBy:與參照控制項之間的關係
toItem:參照的控制項
attribute:參照的控制項約束的類型(做怎樣的約束)
multiplier:約束的控制項和參照的控制項關係倍數
constant:常量
最後兩個參數計算關係:
view1.property1 =(view2.property2 * multiplier)+ constant
二.Autolayout的常見警告和錯誤
1.警告控制項的frame不匹配所添加的約束, 比如:約束控制項的寬度為150, 而控制項現在的寬度是160 2.錯誤缺乏必要的約束, 比如:只約束了寬度和高度, 沒有約束具體的位置兩個約束衝突,比如:1個約束控制項的寬度為150, 1個約束控制項的寬度為160
三.例子
1.代碼實現:
ViewController.m
1 #import "ViewController.h" 2 3 @interface ViewController () 4 5 @end 6 7 @implementation ViewController 8 9 - (void)viewDidLoad {10 [super viewDidLoad];11 //建立添加blueview12 UIView *blueView=[[UIView alloc] init];13 blueView.backgroundColor = [UIColor blueColor];14 blueView.translatesAutoresizingMaskIntoConstraints = NO;//禁止Autoresizing15 [self.view addSubview:blueView];16 17 //建立添加redView18 UIView *redView=[[UIView alloc] init];19 redView.backgroundColor = [UIColor redColor];20 redView.translatesAutoresizingMaskIntoConstraints = NO;21 [self.view addSubview:redView];22 23 // 1.0父View左邊 約束 blueView左邊 3024 NSLayoutConstraint *blueLeftCon=[NSLayoutConstraint constraintWithItem:blueView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1.0 constant:30.0];25 [self.view addConstraint:blueLeftCon];26 27 // 1.1父View頂部 約束 blueView頂部 3028 NSLayoutConstraint *blueTopCon=[NSLayoutConstraint constraintWithItem:blueView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1.0 constant:30.0 ];29 [self.view addConstraint:blueTopCon];30 31 // 1.2父View右邊 約束 blueView右邊 3032 NSLayoutConstraint *blueRightCon= [NSLayoutConstraint constraintWithItem:blueView attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeRight multiplier:1.0 constant:-30 ];33 [self.view addConstraint:blueRightCon];34 35 // 1.3 blueView 相當於 高度設定成5036 NSLayoutConstraint *blueHeightCon=[NSLayoutConstraint constraintWithItem:blueView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:0 constant:50];37 [blueView addConstraint:blueHeightCon];38 39 //2.0 redView 頂部 和 blueView 底部 間距2040 NSLayoutConstraint *redTopCon=[NSLayoutConstraint constraintWithItem:redView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:blueView attribute:NSLayoutAttributeBottom multiplier:1.0 constant:20];41 [self.view addConstraint:redTopCon];42 43 //2.1 redView 左邊 和 blueView 水平中心線對齊44 NSLayoutConstraint *redLeftCon=[NSLayoutConstraint constraintWithItem:redView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:blueView attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0];45 [self.view addConstraint:redLeftCon];46 47 //2.2 redView 右邊 參照 blueView 右邊對齊48 NSLayoutConstraint *redRightCon = [NSLayoutConstraint constraintWithItem:redView attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:blueView attribute:NSLayoutAttributeRight multiplier:1.0 constant:0];49 [self.view addConstraint:redRightCon];50 51 //2.3 redView 高度 參照 blueView 高度相等52 NSLayoutConstraint *redHeightCon=[NSLayoutConstraint constraintWithItem:redView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:blueView attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0];53 [self.view addConstraint:redHeightCon];54 55 }56 57 @endView Code
2.storyboard實現:
效果: