自動布局方法1

/**
 創(chuàng)建約束
 
 @param view1 被約束視圖view1
 @param attr1 被約束視圖的布局屬性
 @param relation 關系屬性
 @param view2 參照視圖view2
 @param attr2 參照視圖view2的布局屬性
 @param multiplier 倍數
 @param c 常數
 @return 約束
 */
+(instancetype)constraintWithItem:(id)view1
                        attribute:(NSLayoutAttribute)attr1
                        relatedBy:(NSLayoutRelation)relation
                           toItem:(nullable id)view2
                        attribute:(NSLayoutAttribute)attr2
                       multiplier:(CGFloat)multiplier
                         constant:(CGFloat)c;

依據的公式是：view1.attr1 = view2.attr2 * multiplier + constant

NSLayoutAttribute（布局屬性）

NSLayoutRelation（關系屬性）

代碼提示

<#被約束視圖#>.translatesAutoresizingMaskIntoConstraints = NO;
    [<#view的父視圖#> addConstraint:[NSLayoutConstraint constraintWithItem:<#被約束視圖#> attribute:(NSLayoutAttribute<#被約束視圖的布局屬性#>) relatedBy:(NSLayoutRelation<#布局屬性的布局關系#>) toItem:<#參照視圖#> attribute:NSLayoutAttribute<#參照視圖的布局屬性#> multiplier:<#倍數#> constant:<#常數#>]];

代碼示例

- (void)codeLayoutConstraint {
   
   //創(chuàng)建背景圖
   UIView *backgroundView = [[UIView alloc] init];
   backgroundView.backgroundColor = [UIColor yellowColor];
   [self.view addSubview:backgroundView];
   backgroundView.translatesAutoresizingMaskIntoConstraints = NO;
   
   //和父視圖等寬
   [self.view addConstraint:[NSLayoutConstraint constraintWithItem:backgroundView attribute:(NSLayoutAttributeWidth) relatedBy:(NSLayoutRelationEqual) toItem:self.view attribute:NSLayoutAttributeWidth multiplier:1 constant:0]];
   
   //二分之一高
   [self.view addConstraint:[NSLayoutConstraint constraintWithItem:backgroundView attribute:(NSLayoutAttributeHeight) relatedBy:(NSLayoutRelationEqual) toItem:self.view attribute:NSLayoutAttributeHeight multiplier:0.5 constant:0]];
   
   //垂直對齊
   [self.view addConstraint:[NSLayoutConstraint constraintWithItem:backgroundView attribute:(NSLayoutAttributeCenterX) relatedBy:(NSLayoutRelationEqual) toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0]];
   
   //水平對齊
   [self.view addConstraint:[NSLayoutConstraint constraintWithItem:backgroundView attribute:(NSLayoutAttributeCenterY) relatedBy:(NSLayoutRelationEqual) toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0]];
   
   
   
   //創(chuàng)建橙色視圖
   UIView *orangeView = [[UIView alloc] init];
   orangeView.backgroundColor = [UIColor orangeColor];
   [backgroundView addSubview:orangeView];
   orangeView.translatesAutoresizingMaskIntoConstraints = NO;

   //上邊距離父視圖上邊20
   [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:orangeView attribute:(NSLayoutAttributeTop) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeTop multiplier:1 constant:20]];
   
   //下邊距離父視圖下邊減20
   [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:orangeView attribute:(NSLayoutAttributeBottom) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeBottom multiplier:1 constant:-20]];
   
   if (/* DISABLES CODE */ (YES)) {//if和else效果一樣
       //前邊距離父視圖前邊20
       [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:orangeView attribute:(NSLayoutAttributeLeading) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeLeading multiplier:1 constant:20]];
       
       //后邊距離父視圖后邊減100
       [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:orangeView attribute:(NSLayoutAttributeTrailing) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeTrailing multiplier:1 constant:-100]];
   } else {
       //左邊距離父視圖前邊20
       [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:orangeView attribute:(NSLayoutAttributeLeft) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeLeft multiplier:1 constant:20]];
       //右邊距離父視圖后邊減100
       [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:orangeView attribute:(NSLayoutAttributeRight) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeRight multiplier:1 constant:-100]];
   }
   
   
   
   
   
   //創(chuàng)建紅色視圖
   UIView *redView = [[UIView alloc] init];
   redView.backgroundColor = [UIColor redColor];
   [backgroundView addSubview:redView];
   redView.translatesAutoresizingMaskIntoConstraints = NO;
   
   //上邊距離父視圖上邊20
   [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:redView attribute:(NSLayoutAttributeTop) relatedBy:(NSLayoutRelationEqual) toItem:backgroundView attribute:NSLayoutAttributeTop multiplier:1 constant:20]];
   
   //高度44
   [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:redView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:44]];
   
   //自身寬高比1:1
   [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:redView attribute:(NSLayoutAttributeHeight) relatedBy:(NSLayoutRelationEqual) toItem:redView attribute:NSLayoutAttributeWidth multiplier:1 constant:0]];
   
   if (/* DISABLES CODE */ (NO)) {//if和else效果一樣
       //左邊距離橙色視圖右邊20
       [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:redView attribute:(NSLayoutAttributeLeft) relatedBy:(NSLayoutRelationEqual) toItem:orangeView attribute:NSLayoutAttributeRight multiplier:1 constant:20]];
   } else {
       //前邊距離橙色視圖后邊20
       [backgroundView addConstraint:[NSLayoutConstraint constraintWithItem:redView attribute:(NSLayoutAttributeLeading) relatedBy:(NSLayoutRelationEqual) toItem:orangeView attribute:NSLayoutAttributeTrailing multiplier:1 constant:20]];
   }
}

自動布局方法2(了解即可)

     @param format 使用VFL格式化的字符串力细，可以參見官方的幫助文檔贪绘；
     @param opts 指定VFL中所有對象的布局屬性和方向净响。舉例：有2個視圖使用VFL進行布局，可以使用NSLayoutFormatAlignAllLeft碎连，就讓兩個視圖左對齊；
     @param metrics 度量或者指標的字典累驮，字典里面有相關的鍵值對來控制相關的度量指標卫枝，通過key獲燃灞；
     @param views 指定約束的視圖：一個或多個剃盾。
    + (NSArray<__kindof NSLayoutConstraint *> *)constraintsWithVisualFormat:(NSString *)format
                                                                    options:(NSLayoutFormatOptions)opts
                                                                    metrics:(nullable NSDictionary<NSString *,id> *)metrics
                                                                      views:(NSDictionary<NSString *, id> *)views;

VFL字符串說明：

VFL字符串說明.png

代碼示例

- (void)codeLayoutConstraint2 {
    
    UIView *yellowView = [[UIView alloc] init];
    yellowView.backgroundColor = [UIColor yellowColor];
    [self.view addSubview:yellowView];
    yellowView.translatesAutoresizingMaskIntoConstraints = NO;
    
    UIView *orangeView = [[UIView alloc] init];
    orangeView.backgroundColor = [UIColor orangeColor];
    [self.view addSubview:orangeView];
    orangeView.translatesAutoresizingMaskIntoConstraints = NO;
    
    UIView *redView = [[UIView alloc] init];
    redView.backgroundColor = [UIColor redColor];
    [self.view addSubview:redView];
    redView.translatesAutoresizingMaskIntoConstraints = NO;
    
    
    //創(chuàng)建VFL約束字符串
    
    //水平順序：父視圖腺占，space個距離，黃色寬100痒谴，5個距離衰伯，橙色視圖，space1個距離积蔚，父視圖
    NSString *hVFL = @"H:|-space-[yellowView(100)]-5-[orangeView]-space1-|";
    
    //水平順序：父視圖意鲸，space個距離，紅色視圖寬和橙色視圖相等
    NSString *hVFL1 = @"H:|-space-[redView(==orangeView)]";
    
    //垂直順序：父視圖尽爆，100個距離怎顾，橙色視圖高100
    NSString *vVFL = @"V:|-100-[orangeView(==100)]";
    
    //垂直順序：父視圖，100個距離漱贱，黃色視圖高100槐雾，5個距離，紅色視圖和橙色視圖高相等
    NSString *vVFL1 = @"V:|-100-[yellowView(==100)]-5-[redView(==orangeView)]";
    
    
    //度量值
    NSDictionary *metircs = @{@"space":@15,@"space1":@30};
    //views
    NSDictionary *views = NSDictionaryOfVariableBindings(yellowView,orangeView,redView);
    
    //創(chuàng)建約束
    NSArray *hconstraint = [NSLayoutConstraint constraintsWithVisualFormat:hVFL options:NSLayoutFormatDirectionLeadingToTrailing metrics:metircs views:views];
    
    NSArray *hconstraint1 = [NSLayoutConstraint constraintsWithVisualFormat:hVFL1 options:NSLayoutFormatAlignAllLeft | NSLayoutFormatAlignAllTop metrics:metircs views:views];
    
    NSArray *vconstraint = [NSLayoutConstraint constraintsWithVisualFormat:vVFL options:NSLayoutFormatDirectionLeadingToTrailing metrics:metircs views:views];
    
    NSArray *vconstraint1 = [NSLayoutConstraint constraintsWithVisualFormat:vVFL1 options:NSLayoutFormatDirectionLeadingToTrailing metrics:metircs views:views];
    
    //添加約束
    [self.view addConstraints:hconstraint];
    
    [self.view addConstraints:hconstraint1];
    
    [self.view addConstraints:vconstraint];
    
    [self.view addConstraints:vconstraint1];
    
}