Coding源码学习第四部分(Masonry介绍与使用(一))-白红宇

Coding源码学习第四部分(Masonry介绍与使用(一))

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发布时间：2019-06-09

本文共 13940 字，大约阅读时间需要 46 分钟。

Masonry GitHub:

Masonry是一个轻量级的布局框架，拥有自己的描述语法，采用更优雅的链式语法封装自动布局，简洁明了并具有高可读性，而且同时支持 iOS 和 Mac OS X。Masonry是一个用代码写iOS或OS界面的库，可以代替Auto layout。

example ：

1 [view1 mas_makeConstraints:^(MASConstraintMaker *make) {    2 3     // 设置和superView 的边缘的缩进量4     make.edges.equalTo(superview).with.insets(padding);5 6 7 }];

Masonry使用讲解

Masonry 支持的属性：

make 的属性：（MASConstraintMaker:）

1 @interface MASConstraintMaker : NSObject 2  3 /** 4  *    The following properties return a new MASViewConstraint 5  *  with the first item set to the makers associated view and the appropriate MASViewAttribute 6  */ 7 @property (nonatomic, strong, readonly) MASConstraint *left; 8 @property (nonatomic, strong, readonly) MASConstraint *top; 9 @property (nonatomic, strong, readonly) MASConstraint *right;10 @property (nonatomic, strong, readonly) MASConstraint *bottom;11 @property (nonatomic, strong, readonly) MASConstraint *leading;12 @property (nonatomic, strong, readonly) MASConstraint *trailing;13 @property (nonatomic, strong, readonly) MASConstraint *width;14 @property (nonatomic, strong, readonly) MASConstraint *height;15 @property (nonatomic, strong, readonly) MASConstraint *centerX;16 @property (nonatomic, strong, readonly) MASConstraint *centerY;17 @property (nonatomic, strong, readonly) MASConstraint *baseline;

其中leading与left trailing与right 在正常情况下是等价的但是当一些布局是从右至左时，则会对调换句话说就是基本可以不理不用用left和right就好了

需要添约束的View 的约束的属性：

1 @interface MAS_VIEW (MASAdditions) 2  3 /** 4  *    following properties return a new MASViewAttribute with current view and appropriate NSLayoutAttribute 5  */ 6 @property (nonatomic, strong, readonly) MASViewAttribute *mas_left; 7 @property (nonatomic, strong, readonly) MASViewAttribute *mas_top; 8 @property (nonatomic, strong, readonly) MASViewAttribute *mas_right; 9 @property (nonatomic, strong, readonly) MASViewAttribute *mas_bottom;10 @property (nonatomic, strong, readonly) MASViewAttribute *mas_leading;11 @property (nonatomic, strong, readonly) MASViewAttribute *mas_trailing;12 @property (nonatomic, strong, readonly) MASViewAttribute *mas_width;13 @property (nonatomic, strong, readonly) MASViewAttribute *mas_height;14 @property (nonatomic, strong, readonly) MASViewAttribute *mas_centerX;15 @property (nonatomic, strong, readonly) MASViewAttribute *mas_centerY;16 @property (nonatomic, strong, readonly) MASViewAttribute *mas_baseline;17 @property (nonatomic, strong, readonly) MASViewAttribute *(^mas_attribute)(NSLayoutAttribute attr);

Masonry 提供了3个关于约束的方法：

1 - (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block; // mas_makeConstraints 只负责新增约束 Autolayout不能同时存在两条针对于同一对象的约束 否则会报错 2 - (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block; // mas_updateConstraints 针对上面的情况 会更新在block中出现的约束 不会导致出现两个相同约束的情况3 - (NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block; // mas_remakeConstraints 则会清除之前的所有约束 仅保留最新的约束4 三种函数善加利用 就可以应对各种情况了

mas_makeConstraints 是给view添加约束，约束有几种，分别是边距，宽，高，左上右下距离，基准线。

添加过约束后可以有修正，修正有offset（位移）修正和multipliedBy（倍率）修正。

语法一般是 make.equalTo or make.greaterThanOrEqualTo or make.lessThanOrEqualTo + 倍数和位移修正。

注意点1：

使用 mas_makeConstraints方法的元素必须事先添加到父元素的中，例如[self.view addSubview:view];

注意点2：

mas_equalTo 和 equalTo 区别：mas_equalTo 比equalTo多了类型转换操作，一般来说，大多数时候两个方法都是通用的，但是对于数值元素使用mas_equalTo。对于对象或是多个属性的处理，使用equalTo。特别是多个属性时，必须使用equalTo.

举例 make.left.and.right.equalTo(self.view) , make.height.mas_equalTo(@20);

1 #define mas_equalTo(...)                 equalTo(MASBoxValue((__VA_ARGS__)))2 #define mas_greaterThanOrEqualTo(...)    greaterThanOrEqualTo(MASBoxValue((__VA_ARGS__)))3 #define mas_lessThanOrEqualTo(...)       lessThanOrEqualTo(MASBoxValue((__VA_ARGS__)))4 5 #define mas_offset(...)                  valueOffset(MASBoxValue((__VA_ARGS__)))

mas_equalTo 是一个宏，可以看到 mas_equalTo只是对其参数进行了一个BOX操作(装箱) MASBoxValue的定义具体可以看看源代码

所支持的类型除了NSNumber支持的那些数值类型之外，就只支持CGPoint CGSize UIEdgeInsets

mas_greaterThanOrEqualTo 和 mas_lessThanOrEqualTo 这两个宏还有一个小技巧:

1 #ifdef MAS_SHORTHAND_GLOBALS2 3 #define equalTo(...)                     mas_equalTo(__VA_ARGS__)4 #define greaterThanOrEqualTo(...)        mas_greaterThanOrEqualTo(__VA_ARGS__)5 #define lessThanOrEqualTo(...)           mas_lessThanOrEqualTo(__VA_ARGS__)6 7 #define offset(...)                      mas_offset(__VA_ARGS__)8 9 #endif

定义以下两个宏,在使用Masonry框架时就不需要加mas_前缀了

(定义宏一定要在引入Masonry.h文件之前).

1 //define this constant if you want to use Masonry without the 'mas_' prefix 2 #define MAS_SHORTHAND 3 //define this constant if you want to enable auto-boxing for default syntax 4 #define MAS_SHORTHAND_GLOBALS 5  6 // example 7  8  9 #define MAS_SHORTHAND10 #define MAS_SHORTHAND_GLOBALS11 #import "Masonry.h"

注意点3: 注意到方法with和and,这连个方法其实没有做任何操作，方法只是返回对象本身，这这个方法的左右完全是为了方法写的时候的可读性。

make.left.and.right.equalTo(self.view);和make.left.right.equalTo(self.view);是完全一样的，但是明显的加了and方法的语句可读性更好点。

1 #pragma mark - Semantic properties2 3 - (MASConstraint *)with {4     return self;5 }6 7 - (MASConstraint *)and {8     return self;9 }

小技巧：#define WS(weakSelf) __weak __typeof(&*self)weakSelf = self; 快速的定义一个weakSelf ，用于block 里面，防止循环引用。

示例：

(1) 居中显示一个View :

1     WS(weakSelf); // WS 是上面定义的一个宏 2     // 从此基本可以抛弃CGRectMake 了 3     UIView *sv = [UIView new]; 4     sv.backgroundColor = [UIColor blackColor]; 5     // 在做autoLayout 之前，一定要将view 添加到superView 上，否则会报错 6     [self.view addSubview:sv]; 7     // mas_makeConstraints 就是Masonry 的autoLayout 添加函数，将所需的约束添加到block 中就行了 8     [sv mas_makeConstraints:^(MASConstraintMaker *make) { 9         // 将sv 居中（很容易理解）10         make.center.equalTo(weakSelf.view);11         // 将size 设置为（400 ，400）12         make.size.mas_equalTo(CGSizeMake(400, 400));13     }];

(2)让一个View 略小于其superView(边距是10)

1     // 让一个View 略小于其superView（边框为 10） 2     UIView *sv1 = [UIView new]; 3     sv1.backgroundColor = [UIColor redColor]; 4     [sv addSubview:sv1]; 5     [sv1 mas_makeConstraints:^(MASConstraintMaker *make) { 6         make.edges.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10)); 7         // 等价于 8 //        make.top.equalTo(sv).with.offset(10); 9 //        make.left.equalTo(sv).with.offset(10);10 //        make.bottom.equalTo(sv).with.offset(-10);11 //        make.right.equalTo(sv).with.offset(-10);12         // 也等价于13 //        make.top.left.bottom.and.right.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10));14     }];

可以看到 edges 其实就是top,left,bottom,right的一个简化分开写也可以一句话更省事

那么为什么bottom和right里的offset是负数呢? 因为这里计算的是绝对的数值计算的bottom需要小于sv的底部高度所以要-10 同理用于right

(3)让两个高度为150 的View 垂直居中且等宽且等间隔排列间隔是10 （自动计算其宽度）

1     // 初级 让两个高度为150 的View 垂直居中且等宽且等间隔排列 间隔为10 （自动计算其宽度） 2     int padding1 = 10; 3     UIView *sv2 = [UIView new]; 4     sv2.backgroundColor = [UIColor yellowColor]; 5     [sv addSubview:sv2]; 6     UIView *sv3 = [UIView new]; 7     sv3.backgroundColor = [UIColor yellowColor]; 8     [sv addSubview:sv3]; 9     10     [sv2 mas_makeConstraints:^(MASConstraintMaker *make) {11         make.centerY.mas_equalTo(sv.mas_centerY);12         make.left.equalTo(sv.mas_left).with.offset(padding1);13         make.right.equalTo(sv3.mas_left).with.offset(-padding1);14         make.height.mas_equalTo(@150);15         make.width.equalTo(sv3);16     }];17 18     [sv3 mas_makeConstraints:^(MASConstraintMaker *make) {19         make.centerY.mas_equalTo(sv.mas_centerY);20         make.left.equalTo(sv2.mas_right).with.offset(padding1);21         make.right.equalTo(sv.mas_right).with.offset(-padding1);22         make.height.mas_equalTo(@150);23         make.width.equalTo(sv2);24     }];

这里我们在两个子view之间互相设置的约束可以看到他们的宽度在约束下自动的被计算出来了

(4)在UIScrollerView 顺序排列一些View 并自动计算contentSize

1     // 中级 在UIScrollerView 顺序排列一些View 并自动计算contentSize 2     UIScrollView *scrollView = [UIScrollView new]; 3     scrollView.backgroundColor = [UIColor whiteColor]; 4     [sv addSubview:scrollView]; 5     [scrollView mas_makeConstraints:^(MASConstraintMaker *make) { 6         make.edges.equalTo(sv).with.insets(UIEdgeInsetsMake(5, 5, 5, 5)); // 约束UIScrollerView 的窗口视图的大小四边各缩进sv 5 7     }]; 8     UIView *container = [UIView new]; // 起一个中间层的作用，能够自动计算UIScrollerView 的contentSize 9     [scrollView addSubview:container];10     [container mas_makeConstraints:^(MASConstraintMaker *make) {11         make.edges.equalTo(scrollView); // left right top bottom 12         make.width.equalTo(scrollView);13     }];14     15     int count = 10;16     UIView *lastView = nil;17     for (int i = 1; i <= count; i++) {18         UIView *subV = [UIView new];19         [container addSubview:subV];20         subV.backgroundColor = [UIColor colorWithHue:(arc4random() % 256 / 256.0) saturation:(arc4random() % 128 / 256.0) brightness:(arc4random() % 128 / 256.0) alpha:1]; // 设置背景颜色21         [subV mas_makeConstraints:^(MASConstraintMaker *make) {22             make.left.and.right.equalTo(container);23             make.height.mas_equalTo(@(20 * i)); // 每个子View 的高度不断增大一倍24             if (lastView) {25                 make.top.mas_equalTo(lastView.mas_bottom); // lastView 做中间View 的传递，确定每个小View 的top26             } else {27                 make.top.mas_equalTo(container.mas_top); // 第一个小View 的top 和container 相等28             }29         }];30         lastView = subV;31     }32     33     [container mas_makeConstraints:^(MASConstraintMaker *make) {34         make.bottom.equalTo(lastView.mas_bottom); // container 的bottom 和最后一个小View 的bottom 相等35     }];

(5)横向或者纵向等间隙的排列一组View

autoLayout并没有直接提供等间隙排列的方法(Masonry的官方demo中也没有对应的案例) 但是参考案例3 我们可以通过一个小技巧来实现这个目的为此写一个Category

1 #import "UIView+Masonry_LJC.h" 2 #import "Masonry.h" 3  4 @implementation UIView (Masonry_LJC) 5  6 - (void)distributeSpacingHorizontallyWith:(NSArray *)views { 7     NSMutableArray *spaces = [NSMutableArray arrayWithCapacity:views.count + 1]; 8      9     for (int i = 0; i < views.count + 1; ++i) {10         UIView *v = [UIView new];11         [spaces addObject:v];12         [self addSubview:v];13         14         [v mas_makeConstraints:^(MASConstraintMaker *make) {15             make.width.equalTo(v.mas_height); // 宽高相等16         }];17     }18     19     UIView *v0 = spaces[0];20     21     __weak __typeof (&*self) ws = self;22     23     [v0 mas_makeConstraints:^(MASConstraintMaker *make) {24         make.left.equalTo(ws.mas_left);25         make.centerY.equalTo(((UIView *)views[0]).mas_centerY);26     }];27     28     UIView *lastSpace = v0;29     for (int i = 0; i < views.count; ++i) {30         UIView *obj = views[i];31         UIView *space = spaces[i + 1];32         33         [obj mas_makeConstraints:^(MASConstraintMaker *make) {34             make.left.equalTo(lastSpace.mas_right);35         }];36         37         [space mas_makeConstraints:^(MASConstraintMaker *make) {38             make.left.equalTo(obj.mas_right);39             make.centerY.equalTo(obj.mas_centerY);40             make.width.equalTo(v0);41         }];42         43         lastSpace = space;44     }45     46     [lastSpace mas_makeConstraints:^(MASConstraintMaker *make) {47         make.right.equalTo(ws.mas_right);48     }];49 }50 51 - (void)distributeSpacingVerticallyWith:(NSArray *)views {52     NSMutableArray *spaces = [NSMutableArray arrayWithCapacity:views.count + 1];53     54     for (int i = 0; i < views.count + 1; ++i) {55         UIView *v = [UIView new];56         [spaces addObject:v];57         [self addSubview:v];58         59         [v mas_makeConstraints:^(MASConstraintMaker *make) {60             make.width.equalTo(v.mas_height);61         }];62     }63     64     UIView *v0 = spaces[0];65     66     __weak __typeof (&*self) ws = self;67     68     [v0 mas_makeConstraints:^(MASConstraintMaker *make) {69         make.top.equalTo(ws.mas_top);70         make.centerX.equalTo(((UIView *)views[0]).mas_centerX);71     }];72     73     UIView *lastSpace = v0;74     for (int i = 0; i < views.count; ++i) {75         UIView *obj = views[i];76         UIView *space = spaces[i + 1];77         78         [obj mas_makeConstraints:^(MASConstraintMaker *make) {79             make.top.equalTo(lastSpace.mas_bottom);80         }];81         82         [space mas_makeConstraints:^(MASConstraintMaker *make) {83             make.top.equalTo(obj.mas_bottom);84             make.centerX.equalTo(obj.mas_centerX);85             make.height.equalTo(v0);86         }];87         88         lastSpace = space;89     }90     91     [lastSpace mas_makeConstraints:^(MASConstraintMaker *make) {92         make.bottom.equalTo(ws.mas_bottom);93     }];94 }95 @end

测试：

1     UIView *sv11 = [UIView new]; 2     UIView *sv12 = [UIView new]; 3     UIView *sv13 = [UIView new]; 4     UIView *sv21 = [UIView new]; 5     UIView *sv31 = [UIView new]; 6     sv11.backgroundColor = [UIColor redColor]; 7     sv12.backgroundColor = [UIColor redColor]; 8     sv13.backgroundColor = [UIColor redColor]; 9     sv21.backgroundColor = [UIColor redColor];10     sv31.backgroundColor = [UIColor redColor];11     [sv addSubview:sv11];12     [sv addSubview:sv12];13     [sv addSubview:sv13];14     [sv addSubview:sv21];15     [sv addSubview:sv31];16     //给予不同的大小 测试效果17     [sv11 mas_makeConstraints:^(MASConstraintMaker *make) {18         make.centerY.equalTo(@[sv12,sv13]);19         make.centerX.equalTo(@[sv21,sv31]);20         make.size.mas_equalTo(CGSizeMake(40, 40));21     }];22     [sv12 mas_makeConstraints:^(MASConstraintMaker *make) {23         make.size.mas_equalTo(CGSizeMake(70, 20));24     }];25     [sv13 mas_makeConstraints:^(MASConstraintMaker *make) {26         make.size.mas_equalTo(CGSizeMake(50, 50));27     }];28     [sv21 mas_makeConstraints:^(MASConstraintMaker *make) {29         make.size.mas_equalTo(CGSizeMake(50, 20));30     }];31     [sv31 mas_makeConstraints:^(MASConstraintMaker *make) {32         make.size.mas_equalTo(CGSizeMake(40, 60));33     }];34     [sv distributeSpacingHorizontallyWith:@[sv11,sv12,sv13]];35     [sv distributeSpacingVerticallyWith:@[sv11,sv21,sv31]];