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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
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
mas_remakeConstraints 则会清除之前的所有约束 仅保留最新的约束
equalTo 和 mas_equalTo的区别在哪里呢? 其实 mas_equalTo是一个MACRO,比较的是值，equalTo比较的是view。
1. [基础] 居中显示一个view
- (void)viewDidLoad{ [super viewDidLoad]; // Do any additional setup after loading the view. 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(300, 300)); }]; }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)); /* 等价于 make.top.equalTo(sv).with.offset(10); make.left.equalTo(sv).with.offset(10); make.bottom.equalTo(sv).with.offset(-10); make.right.equalTo(sv).with.offset(-10); */ /* 也等价于 make.top.left.bottom.and.right.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10)); */}];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);}];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);}];@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); }];}@endUIView *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];
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原文地址：http://www.cnblogs.com/hualuoshuijia/p/5007708.html
