ios - 如何使用 NSLayoutConstraint 将宽度固定到某些 UIView？

Question

如何使用 NSLayoutConstraints 固定两个以上宽度相等的 UIView？

现在，我正在使用以下代码，并且不能固定两个以上的 UIView：

for (int i = 0; i < column.count; i++) {
    NSString *horizontalFormat = @"H:|[view1][view2(==view1)]|";
    NSDictionary *views;
    if (i < column.count - 1) {
        views  = @{
                   @"view1": column[i],
                   @"view2": column[i + 1]
                   };
    }else{
        views  = @{
                   @"view1": column[i - 1],
                   @"view2": column[i]
                   };
    }
    NSArray * horizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:horizontalFormat
                                                                    options:NSLayoutFormatAlignAllTop | NSLayoutFormatAlignAllBottom
                                                                    metrics:nil
                                                                      views:views];
    [self.contentView addConstraints:horizontalConstraints];
}

有任何想法吗？

Answer 1

每个 NSLayoutConstraint 只能关联两个视图，但没有什么能阻止您添加额外的约束。例如：

[NSLayoutConstraint constraintWithItem:column[i-1] attribute: NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:column[i] attribute:NSLayoutAttributeWidth multiplied:1.f constant:0.f];

[NSLayoutConstraint constraintWithItem:column[i+1] attribute: NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:column[i] attribute:NSLayoutAttributeWidth multiplied:1.f constant:0.f];

如果添加这两个约束，i-1、i 和 i+1 处的“列”现在都将具有相等的宽度。

Answer 2

这是一个例子。所有视图都是在代码中生成的，所以只需将此代码复制到 UIViewController 中（例如复制到它的viewDidLoad中）并运行它：

UIView* v1 = [[UIView alloc] init];
v1.layer.borderWidth = 2;
v1.layer.borderColor = [UIColor redColor].CGColor;
v1.translatesAutoresizingMaskIntoConstraints = NO;

[self.view addSubview:v1];
[NSLayoutConstraint activateConstraints:
 @[[v1.topAnchor constraintEqualToAnchor:self.view.topAnchor constant:100],
   [v1.leadingAnchor constraintEqualToAnchor:self.view.leadingAnchor],
   [v1.heightAnchor constraintEqualToConstant:40],
   ]];
NSInteger n = 6; // change this number as desired
NSMutableArray* marr = [NSMutableArray new];
[marr addObject:v1];
for (NSInteger i = 1; i < n; i++) {
    UIView* v = [[UIView alloc] init];
    v.layer.borderWidth = 2;
    v.layer.borderColor = [UIColor redColor].CGColor;
    v.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:v];
    [marr addObject:v];
}
for (NSInteger i = 1; i < n; i++) {
    UIView* v = marr[i];
    UIView* prev = marr[i-1];
    [NSLayoutConstraint activateConstraints:
     @[[v.topAnchor constraintEqualToAnchor:v1.topAnchor],
       [v.bottomAnchor constraintEqualToAnchor:v1.bottomAnchor],
       [v.leadingAnchor constraintEqualToAnchor:prev.trailingAnchor],
       [v.widthAnchor constraintEqualToAnchor:v1.widthAnchor]
       ]];
}
UIView* v = marr[n-1];
[NSLayoutConstraint activateConstraints:
 @[[v.trailingAnchor constraintEqualToAnchor:self.view.trailingAnchor]
  ]];