iOS自动布局行

Question

我试图更好地理解自动布局，并且创建了一些可以帮助我的静态方法。现在我试图在tableview结构中设置一个视图数组（在行中）。这工作挺好。

看到这里我的问题：

要做到这一点我用这个代码：

//In the update constraints method 
UIView *view1 = [self createView]; 
view1.backgroundColor = [UIColor redColor]; 
UIView *view2 = [self createView]; 
view2.backgroundColor = [UIColor yellowColor]; 

[self addSubview:view1]; 
[self addSubview:view2]; 

[self addConstraints:[DXVFL row:@[view1, view2] inView:self]]; 

//The row method 
+ (NSArray *) row:(NSArray const *)views inView:(UIView const *)superview { 
    NSMutableArray *constraints = [NSMutableArray new]; 
    CGFloat multiplier = 1.f/[views count]; 
    UIView *prev = nil; 

    for (UIView *view in views) { 
     if (!view.hidden) { 
      [constraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeWidth multiplier:1.f constant:0.f]]; 
      [constraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeHeight multiplier:multiplier constant:0.f]]; 

      if (prev) { 
       [constraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:prev attribute:NSLayoutAttributeBottom multiplier:1.f constant:0.f]]; 
      } 

      prev = view; 
     } 

    } 
    return [constraints copy]; 
} 

所以这部分工作（我猜）。但是当我想要再次按行分割黄色视图时。视图总是添加到顶部区域？

在更新约束方法我这样做：

UIView *view1 = [self createView]; 
view1.backgroundColor = [UIColor redColor]; 
UIView *view2 = [self createView]; 
view2.backgroundColor = [UIColor yellowColor]; 

[self addSubview:view1]; 
[self addSubview:view2]; 

UIView *view3 = [self createView]; 
UIView *view4 = [self createView]; 
[view2 addSubview:view3]; 
[view2 addSubview:view4]; 

[self addConstraints:[DXVFL row:@[view1, view2] inView:self]]; 
[view2 addConstraints:[DXVFL row:@[view3, view4] inView:view2]]; 

不过，我想在底部的两行？我究竟做错了什么？

Answer 1

关闭我的头顶：

您需要添加一个约束来告诉它对准着眼于上海华顶。目前，您只需设置高度和宽度，但不要告诉它将顶端边缘放在哪里。

试着改变你的代码如下：

if (!prev) { 
    [constraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeTop multiplier:1.f constant:0.f]]; 
} else { 
    [constraints addObject:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:prev attribute:NSLayoutAttributeBottom multiplier:1.f constant:0.f]]; 
}