iOS —— Masonry的Autolayout

頁面布局純寫代碼的三個時期

MagicNumber -> autoresizingMask -> autolayout

Masonry是一個輕量級的布局架構，擁有自己的描述文法，采用更優雅的鍊式文法封裝自動布局，簡潔明了，并具有高可讀性，而且同時支援 iOS 和 Max OS X。

AutoLayout和Autoresizing Mask的差別　　

•在iOS6之前，關于螢幕旋轉的适配和iPhone，iPad螢幕的自動适配，基本都是由Autoresizing Mask來完成的。但是随着大家對iOS App的要求越來越高，以及今後可能出現的多種螢幕和分辨率的裝置，Autoresizing Mask顯得有些落伍和遲鈍了。AutoLayout可以完成所有原來Autoresizing Mask能完成的工作，同時還能勝任一些原來無法完成的任務，其中包括：

•AutoLayout可以指定任意兩個view的相對位置，而不需要像Autoresizing Mask那樣需要兩個view在直系的view hierarchy中

•AutoLayout不必須指定相等關系的限制，它可以指定非相等限制（大于或者小于等）；而Autoresizing Mask所能做的布局隻能是相等條件的

•AutoLayout可以指定限制的優先級，計算frame時将優先按照滿足優先級高的條件進行計算

官方的sample code下Masonry

[view1 mas_makeConstraints:^(MASConstraintMaker *make) {

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

}];

Masonry支援的屬性

@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;

這些屬性與NSLayoutAttrubute的對照表

iOS —— Masonry的Autolayout

其中leading與left trailing與right 在正常情況下是等價的，但是當一些布局是從右至左時(比如阿拉伯文?沒有類似的經驗) 則會對調，換句話說就是基本可以不理不用，用left和right就好了。

在ios8釋出後，又新增了一堆奇奇怪怪的屬性(有興趣的朋友可以去瞅瞅)， Masonry暫時還不支援(不過你要支援ios6,ios7 就沒必要去管那麼多了) 。

MACRO

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

superView都是一個size為(300,300)的UIView)

1.居中顯示一個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限制有三個函數：

- (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的差別： mas_equalTo是一個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隻是對其參數進行了BOX操作(裝箱) MASBoxValue的定義具體可以看看源代碼

所支援的類型除了NSNumber支援的那些數值類型之外就隻支援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 其實就是top,left,bottom,right的一個簡化分開寫也可以一句話更省事

那麼為什麼bottom和right裡的offset是負數呢? 因為這裡計算的是絕對的數值計算的bottom需要小魚sv的底部高度是以要-10 同理用于right

這裡有意思的地方是and和with 其實這兩個函數什麼事情都沒做

- (MASConstraint *)with {

return self;

}

- (MASConstraint *)and {

return self;

}

3. 兩個高度為150的view垂直居中且等寬且等間隔排列間隔為10(自動計算其寬度)

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順序排列一些view并自動計算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);

}];

頭部

iOS —— Masonry的Autolayout

尾部

iOS —— Masonry的Autolayout

這裡的關鍵就在于container這個view起到了一個中間層的作用能夠自動的計算uiscrollView的contentSize

5. 橫向或者縱向等間隙的排列一組view

很遺憾 autoLayout并沒有直接提供等間隙排列的方法(Masonry的官方demo中也沒有對應的案例)

@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

簡單的來測試一下

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];

//給予不同的大小測試效果

[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來填充我們目标view的旁邊這點通過圖上的空白标注可以看出來。

覺得意猶未盡呢，請下載下傳官方的demo學習。

(來自:裡脊串)

iOS —— Masonry的Autolayout

繼續閱讀

iOS 8 AutoLayOut入門

使用系統自帶方法代碼,VFL, Masonry實作Autolayout

AutoLayout下代碼更新contraints的實作

iOS autoresizingMask與autoLayout

Autolayout 描述限制（constraint）文法

Storyboard使用技巧：使用比例方式布局

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使用編碼添加限制的規則

Auto LayoutAuto Layout的由來Auto Layout的限制(Constraint)

iOS開發——線性布局神器UIStackView

第一次使用Masonry，一運作就奔潰。。。