Masonry仍然在积极维护，我们致力于修复错误并合并社区中高价值的PR。然而，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性和更简单的API。
Masonry是一个轻量级的布局框架，它使用更简洁的语法包装了AutoLayout。Masonry有自己的布局DSL（领域特定语言），提供了一种可连续描述NSLayoutConstraints的方式，使得布局代码更简洁、易读。Masonry支持iOS和Mac OS X。
有关示例，请参阅Masonry工作区中的Masonry iOS 示例项目。下载后，您需要运行 pod install。
在内部，Auto Layout是一种强大而灵活的方式来组织和布局视图。然而，从代码创建约束是冗长的，并且不太具有描述性。想象这样一个简单的例子，即您希望视图填充其父视图，但每边都要缩进10像素
UIView *superview = self.view;
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],
]];即使是这样一个简单的例子，所需的代码也是相当冗长的，当有2或3个以上的视图时，代码很快就变得难以阅读。另一个选择是使用Visual Format Language (VFL)，它稍微短一些。然而，ASCII类型的语法有其自身的缺陷，并且由于NSLayoutConstraint constraintsWithVisualFormat:返回一个数组，因此它也稍微难于动画。
以下是使用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);
}];甚至更短
[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(superview).with.insets(padding);
}];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将自动将约束添加到适当的视图中。
Masonry还将为您调用view1.translatesAutoresizingMaskIntoConstraints = NO;。
.equalTo等价于 NSLayoutRelationEqual
.lessThanOrEqualTo等价于 NSLayoutRelationLessThanOrEqual
.greaterThanOrEqualTo等价于 NSLayoutRelationGreaterThanOrEqual
这三个相等约束接受一个参数，可以是以下之一
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 |
如果你想让 view 的左边距大于等于 label 的左边距
//these two constraints are exactly the same
make.left.greaterThanOrEqualTo(label);
make.left.greaterThanOrEqualTo(label.mas_left);自动布局允许将宽度和高度设置为固定值。如果你想让视图有最小和最大宽度，可以向等式块传递一个数字
//width >= 200 && width <= 400
make.width.greaterThanOrEqualTo(@200);
make.width.lessThanOrEqualTo(@400)然而，自动布局不允许将左、右、centerY 等对齐属性设置为固定值。所以如果你为这些属性传递一个 NSNumber，Masonry 将将其转换为相对于视图的父视图的约束，即
//creates view.left = view.superview.left + 10
make.left.lessThanOrEqualTo(@10)你可以使用原始类型和结构体来构建你的约束，例如
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 mas_ 前缀开头。在不使用前缀的情况下，通过在导入 Masonry 之前定义 MAS_SHORTHAND_GLOBALS 来使用
一个包含前面任何类型的混合数组的数组
make.height.equalTo(@[view1.mas_height, view2.mas_height]);
make.height.equalTo(@[view1, view2]);
make.left.equalTo(@[view1, @100, view3.right]);
.priority允许你指定一个精确的优先级
.priorityHigh等同于 UILayoutPriorityDefaultHigh
.priorityMedium高低之间的中间值
.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 还提供了一些方便的方法来同时创建多个约束。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))你可以通过链式调用视图属性来提高可读性
// All edges but the top should equal those of the superview
make.left.right.and.bottom.equalTo(superview);
make.top.equalTo(otherView);有时候你需要修改现有的约束，以便进行动画或删除/替换约束。在 Masonry 中，有几种不同的方法来更新约束。
你可以通过将一个约束生成表达式的结果赋给局部变量或类属性来持有特定约束的引用。你也可以通过将多个约束存储在数组中来自引用多个约束。
// 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 功能性用于更新一组约束，但做任何超出更新常量值的操作可能会非常繁琐。这时就需要用到 mas_remakeConstraints。
mas_remakeConstraints 与 mas_updateConstraints 类似，但它不是更新常量值，而是在重新安装之前会先移除其所有约束。这样可以让你提供不同的约束而不必保留要移除的约束的引用。
- (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);
}
}];
}在 Masonry iOS 示例 项目中，你可以找到关于这三种方法更详细的例子。
布局视图不总是按计划进行。所以当事情真的出现问题时，你不想看到这样的控制台输出：
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 添加了一个分类，它重写了默认的 - (NSString *)description 实现。现在你可以为视图和约束提供有意义的名称，并且可以轻松找到由 Masonry 创建的约束。
这意味着你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>要了解如何设置此配置，请查看 Masonry 仓库中的 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在你的 Podfile 中
pod 'Masonry'
如果你想使用 Masonry 而不需要那些讨厌的 'mas_' 前缀，请在导入 Masonry 之前在 prefix.pch 中添加 #define MAS_SHORTHAND
#define MAS_SHORTHAND
忙碌起来，大干快上
#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>}];