iOS —— Masonry的Autolayout

页面布局纯写代码的三个时期

MagicNumber -> autoresizingMask -> autolayout

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 Max OS X。

AutoLayout和Autoresizing Mask的区别　　

•在iOS6之前，关于屏幕旋转的适配和iPhone，iPad屏幕的自动适配，基本都是由Autoresizing Mask来完成的。但是随着大家对iOS App的要求越来越高，以及今后可能出现的多种屏幕和分辨率的设备，Autoresizing Mask显得有些落伍和迟钝了。AutoLayout可以完成所有原来Autoresizing Mask能完成的工作，同时还能胜任一些原来无法完成的任务，其中包括：

•AutoLayout可以指定任意两个view的相对位置，而不需要像Autoresizing Mask那样需要两个view在直系的view hierarchy中

•AutoLayout不必须指定相等关系的约束，它可以指定非相等约束（大于或者小于等）；而Autoresizing Mask所能做的布局只能是相等条件的

•AutoLayout可以指定约束的优先级，计算frame时将优先按照满足优先级高的条件进行计算

官方的sample code下Masonry

[view1 mas_makeConstraints:^(MASConstraintMaker *make) {

make.edges.equalTo(superview).with.insets(padding);

}];

Masonry支持的属性

@property (nonatomic, strong, readonly) MASConstraint *left;

@property (nonatomic, strong, readonly) MASConstraint *top;

@property (nonatomic, strong, readonly) MASConstraint *right;

@property (nonatomic, strong, readonly) MASConstraint *bottom;

@property (nonatomic, strong, readonly) MASConstraint *leading;

@property (nonatomic, strong, readonly) MASConstraint *trailing;

@property (nonatomic, strong, readonly) MASConstraint *width;

@property (nonatomic, strong, readonly) MASConstraint *height;

@property (nonatomic, strong, readonly) MASConstraint *centerX;

@property (nonatomic, strong, readonly) MASConstraint *centerY;

@property (nonatomic, strong, readonly) MASConstraint *baseline;

这些属性与NSLayoutAttrubute的对照表

iOS —— Masonry的Autolayout

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(比如阿拉伯文?没有类似的经验) 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。

在ios8发布后，又新增了一堆奇奇怪怪的属性(有兴趣的朋友可以去瞅瞅)， Masonry暂时还不支持(不过你要支持ios6,ios7 就没必要去管那么多了) 。

MACRO

#define WS(weakSelf) __weak __typeof(&*self)weakSelf = self;

superView都是一个size为(300,300)的UIView)

1.居中显示一个view

- (void)viewDidLoad {

[super viewDidLoad];

WS(ws);

UIView *sv = [UIView new];

[sv showPlaceHolder];

sv.backgroundColor = [UIColor blackColor];

[self.view addSubview:sv];

[sv mas_makeConstraints:^(MASConstraintMaker *make) {

make.center.equalTo(ws.view);

make.size.mas_equalTo(CGSizeMake(320, 320));

}];
}

iOS —— Masonry的Autolayout

Masonry中添加autolayout约束有三个函数：

- (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block;

- (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block;

- (NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block;

其 equalTo 和 mas_equalTo的区别： mas_equalTo是一个MACRO

#define mas_equalTo(...) equalTo(MASBoxValue((__VA_ARGS__)))

#define mas_greaterThanOrEqualTo(...) greaterThanOrEqualTo(MASBoxValue((__VA_ARGS__)))

#define mas_lessThanOrEqualTo(...) lessThanOrEqualTo(MASBoxValue((__VA_ARGS__)))

#define mas_offset(...) valueOffset(MASBoxValue((__VA_ARGS__)))

mas_equalTo只是对其参数进行了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

2.view略小于其superView

UIView *sv1 = [UIView new];

[sv1 showPlaceHolder];

sv1.backgroundColor = [UIColor redColor];

[sv addSubview:sv1];

[sv1 mas_makeConstraints:^(MASConstraintMaker *make) {

make.edges.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10));

}];

iOS —— Masonry的Autolayout

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需要小鱼sv的底部高度所以要-10 同理用于right

这里有意思的地方是and和with 其实这两个函数什么事情都没做

- (MASConstraint *)with {

return self;

}

- (MASConstraint *)and {

return self;

}

3. 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)

int padding1 = 10;

[sv2 mas_makeConstraints:^(MASConstraintMaker *make) {

make.centerY.mas_equalTo(sv.mas_centerY);

make.left.equalTo(sv.mas_left).with.offset(padding1);

make.right.equalTo(sv3.mas_left).with.offset(-padding1);

make.height.mas_equalTo(@150);

make.width.equalTo(sv3);

}];

[sv3 mas_makeConstraints:^(MASConstraintMaker *make) {

make.centerY.mas_equalTo(sv.mas_centerY);

make.left.equalTo(sv2.mas_right).with.offset(padding1);

make.right.equalTo(sv.mas_right).with.offset(-padding1);

make.height.mas_equalTo(@150);

make.width.equalTo(sv2);

}];

iOS —— Masonry的Autolayout

4. UIScrollView顺序排列一些view并自动计算contentSize

UIScrollView *scrollView = [UIScrollView new];

scrollView.backgroundColor = [UIColor whiteColor];

[sv addSubview:scrollView];

[scrollView mas_makeConstraints:^(MASConstraintMaker *make) {

make.edges.equalTo(sv).with.insets(UIEdgeInsetsMake(5,5,5,5));

}];

UIView *container = [UIView new];

[scrollView addSubview:container];

[container mas_makeConstraints:^(MASConstraintMaker *make) {

make.edges.equalTo(scrollView);

make.width.equalTo(scrollView);

}];

int count = 10;

UIView *lastView = nil;

for ( int i = 1 ; i <= count ; ++i )

{

UIView *subv = [UIView new];

[container addSubview:subv];

subv.backgroundColor = [UIColor colorWithHue:( arc4random() % 256 / 256.0 )

saturation:( arc4random() % 128 / 256.0 ) + 0.5

brightness:( arc4random() % 128 / 256.0 ) + 0.5

alpha:1];

[subv mas_makeConstraints:^(MASConstraintMaker *make) {

make.left.and.right.equalTo(container);

make.height.mas_equalTo(@(20*i));

if ( lastView ) {

make.top.mas_equalTo(lastView.mas_bottom);

} else {

make.top.mas_equalTo(container.mas_top);

}

}];

lastView = subv;

}

[container mas_makeConstraints:^(MASConstraintMaker *make) {

make.bottom.equalTo(lastView.mas_bottom);

}];

头部

iOS —— Masonry的Autolayout

尾部

iOS —— Masonry的Autolayout

这里的关键就在于container这个view起到了一个中间层的作用能够自动的计算uiscrollView的contentSize

5. 横向或者纵向等间隙的排列一组view

很遗憾 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)

@implementation UIView(Masonry_LJC)

- (void) distributeSpacingHorizontallyWith:(NSArray*)views

{

NSMutableArray *spaces = [NSMutableArray arrayWithCapacity:views.count+1];

for ( int i = 0 ; i < views.count+1 ; ++i )

{

UIView *v = [UIView new];

[spaces addObject:v];

[self addSubview:v];

[v mas_makeConstraints:^(MASConstraintMaker *make) {

make.width.equalTo(v.mas_height);

}];

}

UIView *v0 = spaces[0];

__weak __typeof(&*self)ws = self;

[v0 mas_makeConstraints:^(MASConstraintMaker *make) {

make.left.equalTo(ws.mas_left);

make.centerY.equalTo(((UIView*)views[0]).mas_centerY);

}];

UIView *lastSpace = v0;

for ( int i = 0 ; i < views.count; ++i )

{

UIView *obj = views[i];

UIView *space = spaces[i+1];

[obj mas_makeConstraints:^(MASConstraintMaker *make) {

make.left.equalTo(lastSpace.mas_right);

}];

[space mas_makeConstraints:^(MASConstraintMaker *make) {

make.left.equalTo(obj.mas_right);

make.centerY.equalTo(obj.mas_centerY);

make.width.equalTo(v0);

}];

lastSpace = space;

}

[lastSpace mas_makeConstraints:^(MASConstraintMaker *make) {

make.right.equalTo(ws.mas_right);

}];

}

- (void) distributeSpacingVerticallyWith:(NSArray*)views

{

NSMutableArray *spaces = [NSMutableArray arrayWithCapacity:views.count+1];

for ( int i = 0 ; i < views.count+1 ; ++i )

{

UIView *v = [UIView new];

[spaces addObject:v];

[self addSubview:v];

[v mas_makeConstraints:^(MASConstraintMaker *make) {

make.width.equalTo(v.mas_height);

}];

}

UIView *v0 = spaces[0];

__weak __typeof(&*self)ws = self;

[v0 mas_makeConstraints:^(MASConstraintMaker *make) {

make.top.equalTo(ws.mas_top);

make.centerX.equalTo(((UIView*)views[0]).mas_centerX);

}];

UIView *lastSpace = v0;

for ( int i = 0 ; i < views.count; ++i )

{

UIView *obj = views[i];

UIView *space = spaces[i+1];

[obj mas_makeConstraints:^(MASConstraintMaker *make) {

make.top.equalTo(lastSpace.mas_bottom);

}];

[space mas_makeConstraints:^(MASConstraintMaker *make) {

make.top.equalTo(obj.mas_bottom);

make.centerX.equalTo(obj.mas_centerX);

make.height.equalTo(v0);

}];

lastSpace = space;

}

[lastSpace mas_makeConstraints:^(MASConstraintMaker *make) {

make.bottom.equalTo(ws.mas_bottom);

}];

}

@end

简单的来测试一下

UIView *sv11 = [UIView new];

UIView *sv12 = [UIView new];

UIView *sv13 = [UIView new];

UIView *sv21 = [UIView new];

UIView *sv31 = [UIView new];

sv11.backgroundColor = [UIColor redColor];

sv12.backgroundColor = [UIColor redColor];

sv13.backgroundColor = [UIColor redColor];

sv21.backgroundColor = [UIColor redColor];

sv31.backgroundColor = [UIColor redColor];

[sv addSubview:sv11];

[sv addSubview:sv12];

[sv addSubview:sv13];

[sv addSubview:sv21];

[sv addSubview:sv31];

//给予不同的大小测试效果

[sv11 mas_makeConstraints:^(MASConstraintMaker *make) {

make.centerY.equalTo(@[sv12,sv13]);

make.centerX.equalTo(@[sv21,sv31]);

make.size.mas_equalTo(CGSizeMake(40, 40));

}];

[sv12 mas_makeConstraints:^(MASConstraintMaker *make) {

make.size.mas_equalTo(CGSizeMake(70, 20));

}];

[sv13 mas_makeConstraints:^(MASConstraintMaker *make) {

make.size.mas_equalTo(CGSizeMake(50, 50));

}];

[sv21 mas_makeConstraints:^(MASConstraintMaker *make) {

make.size.mas_equalTo(CGSizeMake(50, 20));

}];

[sv31 mas_makeConstraints:^(MASConstraintMaker *make) {

make.size.mas_equalTo(CGSizeMake(40, 60));

}];

[sv distributeSpacingHorizontallyWith:@[sv11,sv12,sv13]];

[sv distributeSpacingVerticallyWith:@[sv11,sv21,sv31]];

[sv showPlaceHolderWithAllSubviews];

[sv hidePlaceHolder];

效果

iOS —— Masonry的Autolayout

技巧就是使用空白的占位view来填充我们目标view的旁边这点通过图上的空白标注可以看出来。

觉得意犹未尽呢，请下载官方的demo学习。

(来自:里脊串)

iOS —— Masonry的Autolayout

继续阅读

iOS 8 AutoLayOut入门

使用系统自带方法代码,VFL, Masonry实现Autolayout

AutoLayout下代码更新contraints的实现

iOS autoresizingMask与autoLayout

Autolayout 描述约束（constraint）语法

Storyboard使用技巧：使用比例方式布局

屏幕适配、Autoresizing、Autolayout屏幕适配、Autoresizing、Autolayout、

Masonry 解析Masonry 解析

Masonry布局框架的使用

iOS 第三方框架－Masonry的使用Masonry配置Masonry使用讲解Masonry实例

iOS_无限滚动

iOS开发之进阶篇（12）—— 屏幕适配1. layoutSubviews2. Constrain to margins3. Constraints4. safeAreaLayoutGuide5. Masonry6. SnapKit

使用编码添加约束的规则

Auto LayoutAuto Layout的由来Auto Layout的约束(Constraint)

iOS开发——线性布局神器UIStackView

第一次使用Masonry，一运行就奔溃。。。