Masonry仍处于积极维护状态，我们致力于修复错误并合并社区中高质量的提交。但是如果您在项目中使用Swift，我们建议使用SnapKit，因为它提供了更好的类型安全并具有更简单的API。
Masonry是一个轻量级的布局框架，它使用更友好的语法封装了AutoLayout。Masonry拥有自己的布局DSL，它以链式方式描述NSLayoutConstraints，从而生成的布局代码更加简洁易读。Masonry支持iOS和Mac OS X。
关于示例，请查看Masonry工作区中的“Masonry iOS Examples”项目。下载后，您需要运行pod install。
在内部，Auto Layout是一种强大且灵活的方式来组织和布局您的视图。然而，从代码中创建约束既冗长又不易描述。想象一个简单的例子，你想让一个视图填充其父视图，但每边都内缩10个像素
UIView *superview = self;
UIView *view1 = [[UIView alloc] init];
view1.translatesAutoresizingMaskIntoConstraints = NO;
view1.backgroundColor = [UIColor greenColor];
[superview addSubview:view1];
UIEdgeInsets padding = UIEdgeInsetsMake(10, 10, 10, 10);
[superview addConstraints:@[
//view1 constraints
[NSLayoutConstraint constraintWithItem:view1
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:padding.top],
[NSLayoutConstraint constraintWithItem:view1
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeLeft
multiplier:1.0
constant:padding.left],
[NSLayoutConstraint constraintWithItem:view1
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:-padding.bottom],
[NSLayoutConstraint constraintWithItem:view1
attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:superview
attribute:NSLayoutAttributeRight
multiplier:1
constant:-padding.right],
]];即使是这样简单的例子，所需的代码也很冗长，当有超过2或3个视图时，代码很快就会变得难以阅读。另一个选择是使用视觉格式语言（VFL），它比VFL更短，但ASCII类型语法有自己的陷阱，而且也不容易动画，因为NSLayoutConstraint constraintsWithVisualFormat:返回一个数组。
这是使用MASConstraintMaker创建的相同约束
UIEdgeInsets padding = UIEdgeInsetsMake(10, 10, 10, 10);
[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(superview.mas_top).with.offset(padding.top); //with is an optional semantic filler
make.left.equalTo(superview.mas_left).with.offset(padding.left);
make.bottom.equalTo(superview.mas_bottom).with.offset(-padding.bottom);
make.right.equalTo(superview.mas_right).with.offset(-padding.right);
}];或者更简洁
[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(superview).with.insets(padding);
}];请注意，在第一个示例中，我们必须将约束添加到父视图中[superview addConstraints:...。然而，Masonry会自动将约束添加到合适的视图中。
Masonry还会为您调用view1.translatesAutoresizingMaskIntoConstraints = NO;。
.equalTo等价于 NSLayoutRelationEqual
.lessThanOrEqualTo等价于 NSLayoutRelationLessThanOrEqual
.greaterThanOrEqualTo等价于 NSLayoutRelationGreaterThanOrEqual
这三个等值约束接受一个参数，可以是以下任何一种
make.centerX.lessThanOrEqualTo(view2.mas_left);| MASViewAttribute | NSLayoutAttribute |
|---|---|
| view.mas_left | NSLayoutAttributeLeft |
| view.mas_right | NSLayoutAttributeRight |
| view.mas_top | NSLayoutAttributeTop |
| view.mas_bottom | NSLayoutAttributeBottom |
| view.mas_leading | NSLayoutAttributeLeading |
| view.mas_trailing | NSLayoutAttributeTrailing |
| view.mas_width | NSLayoutAttributeWidth |
| view.mas_height | NSLayoutAttributeHeight |
| view.mas_centerX | NSLayoutAttributeCenterX |
| view.mas_centerY | NSLayoutAttributeCenterY |
| view.mas_baseline | NSLayoutAttributeBaseline |
如果你想将 view.left 设置为大于或等于 label.left
//these two constraints are exactly the same
make.left.greaterThanOrEqualTo(label);
make.left.greaterThanOrEqualTo(label.mas_left);Auto Layout 允许宽度（width）和高度（height）设置为常量值。如果你想要设置 view 的最小和最大宽度，你可以为等式块传递一个数值
//width >= 200 && width <= 400
make.width.greaterThanOrEqualTo(@200);
make.width.lessThanOrEqualTo(@400)然而，Auto Layout 不允许对齐属性（如 left、right、centerY 等）设置为常量值。所以，如果你为这些属性传递 NSNumber，Masonry 会将这些转换为与视图的父视图相关的约束，即
//creates view.left = view.superview.left + 10
make.left.lessThanOrEqualTo(@10)除了使用 NSNumber，你还可以使用原始类型和结构体来构建你的约束，如下所示
make.top.mas_equalTo(42);
make.height.mas_equalTo(20);
make.size.mas_equalTo(CGSizeMake(50, 100));
make.edges.mas_equalTo(UIEdgeInsetsMake(10, 0, 10, 0));
make.left.mas_equalTo(view).mas_offset(UIEdgeInsetsMake(10, 0, 10, 0));默认情况下，支持自动装箱的宏以前缀 mas_ 开头。可以通过在导入 Masonry 之前定义 MAS_SHORTHAND_GLOBALS 来使用不带前缀的版本。
一个混合了前面任何类型数组的数组
make.height.equalTo(@[view1.mas_height, view2.mas_height]);
make.height.equalTo(@[view1, view2]);
make.left.equalTo(@[view1, @100, view3.right]);
.priority允许你指定一个确切的优先级
.priorityHigh等同于 UILayoutPriorityDefaultHigh
.priorityMedium在高和低之间
.priorityLow等同于 UILayoutPriorityDefaultLow
优先级可以作为约束链的结尾附加，如下所示
make.left.greaterThanOrEqualTo(label.mas_left).with.priorityLow();
make.top.equalTo(label.mas_top).with.priority(600);Masonry 还提供了几个便利方法来同时创建多条约束。这些被称为 MASCompositeConstraints
// make top, left, bottom, right equal view2
make.edges.equalTo(view2);
// make top = superview.top + 5, left = superview.left + 10,
// bottom = superview.bottom - 15, right = superview.right - 20
make.edges.equalTo(superview).insets(UIEdgeInsetsMake(5, 10, 15, 20))// make width and height greater than or equal to titleLabel
make.size.greaterThanOrEqualTo(titleLabel)
// make width = superview.width + 100, height = superview.height - 50
make.size.equalTo(superview).sizeOffset(CGSizeMake(100, -50))// make centerX and centerY = button1
make.center.equalTo(button1)
// make centerX = superview.centerX - 5, centerY = superview.centerY + 10
make.center.equalTo(superview).centerOffset(CGPointMake(-5, 10))你可以链式调用视图属性以提高可读性
// All edges but the top should equal those of the superview
make.left.right.and.bottom.equalTo(superview);
make.top.equalTo(otherView);有时你需要修改现有约束以进行动画或删除/替换约束。在 Masonry 中有几种不同的方法来更新约束。
你可以通过将约束创建表达式的结果分配给局部变量或类属性来保存特定约束的引用。你还可以将多个约束存储在数组中以进行引用。
// in public/private interface
@property (nonatomic, strong) MASConstraint *topConstraint;
...
// when making constraints
[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
self.topConstraint = make.top.equalTo(superview.mas_top).with.offset(padding.top);
make.left.equalTo(superview.mas_left).with.offset(padding.left);
}];
...
// then later you can call
[self.topConstraint uninstall];或者，如果你只更新约束的常量值，你可以使用方便的方法 mas_updateConstraints 而不是 mas_makeConstraints。
// this is Apple's recommended place for adding/updating constraints
// this method can get called multiple times in response to setNeedsUpdateConstraints
// which can be called by UIKit internally or in your code if you need to trigger an update to your constraints
- (void)updateConstraints {
[self.growingButton mas_updateConstraints:^(MASConstraintMaker *make) {
make.center.equalTo(self);
make.width.equalTo(@(self.buttonSize.width)).priorityLow();
make.height.equalTo(@(self.buttonSize.height)).priorityLow();
make.width.lessThanOrEqualTo(self);
make.height.lessThanOrEqualTo(self);
}];
//according to apple super should be called at end of method
[super updateConstraints];
}mas_updateConstraints 对于更新一组约束很有用，但除了更新常量值之外，做任何事情都可能感到疲惫。这就是 mas_remakeConstraints 出现的地方。
mas_remakeConstraints 与 mas_updateConstraints 类似，但不同之处在于，它不是更新常量值，而是在重新安装之前先移除所有的约束。这使得您可以在不保留要删除的约束引用的情况下提供不同的约束。
- (void)changeButtonPosition {
[self.button mas_remakeConstraints:^(MASConstraintMaker *make) {
make.size.equalTo(self.buttonSize);
if (topLeft) {
make.top.and.left.offset(10);
} else {
make.bottom.and.right.offset(-10);
}
}];
}您可以在 Masonry iOS 示例 项目中找到所有三种方法的更详细示例。
布局视图并不总是按照计划进行。因此，当事情真正变得一团糟时，您不想查看这样的控制台输出
Unable to simultaneously satisfy constraints.....blah blah blah....
(
"<NSLayoutConstraint:0x7189ac0 V:[UILabel:0x7186980(>=5000)]>",
"<NSAutoresizingMaskLayoutConstraint:0x839ea20 h=--& v=--& V:[MASExampleDebuggingView:0x7186560(416)]>",
"<NSLayoutConstraint:0x7189c70 UILabel:0x7186980.bottom == MASExampleDebuggingView:0x7186560.bottom - 10>",
"<NSLayoutConstraint:0x7189560 V:|-(1)-[UILabel:0x7186980] (Names: '|':MASExampleDebuggingView:0x7186560 )>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x7189ac0 V:[UILabel:0x7186980(>=5000)]>Masonry 为 NSLayoutConstraint 添加了一个类别，它覆盖了默认的 - (NSString *)description 实现。现在您可以给视图和约束取有意义的名称，并且可以轻松地找到由 Masonry 创建的约束。
这意味着您的控制台输出现在可以像这样
Unable to simultaneously satisfy constraints......blah blah blah....
(
"<NSAutoresizingMaskLayoutConstraint:0x8887740 MASExampleDebuggingView:superview.height == 416>",
"<MASLayoutConstraint:ConstantConstraint UILabel:messageLabel.height >= 5000>",
"<MASLayoutConstraint:BottomConstraint UILabel:messageLabel.bottom == MASExampleDebuggingView:superview.bottom - 10>",
"<MASLayoutConstraint:ConflictingConstraint[0] UILabel:messageLabel.top == MASExampleDebuggingView:superview.top + 1>"
)
Will attempt to recover by breaking constraint
<MASLayoutConstraint:ConstantConstraint UILabel:messageLabel.height >= 5000>有关如何设置此示例，请参阅 Masonry 工作区中的 Masonry iOS 示例 项目。
@implementation DIYCustomView
- (id)init {
self = [super init];
if (!self) return nil;
// --- Create your views here ---
self.button = [[UIButton alloc] init];
return self;
}
// tell UIKit that you are using AutoLayout
+ (BOOL)requiresConstraintBasedLayout {
return YES;
}
// this is Apple's recommended place for adding/updating constraints
- (void)updateConstraints {
// --- remake/update constraints here
[self.button remakeConstraints:^(MASConstraintMaker *make) {
make.width.equalTo(@(self.buttonSize.width));
make.height.equalTo(@(self.buttonSize.height));
}];
//according to apple super should be called at end of method
[super updateConstraints];
}
- (void)didTapButton:(UIButton *)button {
// --- Do your changes ie change variables that affect your layout etc ---
self.buttonSize = CGSize(200, 200);
// tell constraints they need updating
[self setNeedsUpdateConstraints];
}
@end在您的 Podfile 中
pod 'Masonry'
如果您想要使用 Masonry 而不带那些讨厌的 'mas_' 前缀，请在导入 Masonry 之前在 prefix.pch 中添加 #define MAS_SHORTHAND
#define MAS_SHORTHAND
开始 Masonry 编程
#import "Masonry.h"
将包含的代码片段复制到 ~/Library/Developer/Xcode/UserData/CodeSnippets，以便以闪电般的速度编写 Masonry 块！
mas_make -> [<view> mas_makeConstraints:^(MASConstraintMaker *make){<code>}];
mas_update -> [<view> mas_updateConstraints:^(MASConstraintMaker *make){<code>}];
mas_remake -> [<view> mas_remakeConstraints:^(MASConstraintMaker *make){<code>}];