Masonry是一個輕量級的布局框架，采用更好的語法封裝自動布局，它有自己的布局DSL。簡潔明了并具有高可讀性 而且同時支持 iOS 和 Max OS X。
下載
NSLayoutConstraints的缺點
NSLayoutConstraints是一個強大且靈活的自動布局架構(gòu)，可是通過代碼創(chuàng)建的約束是十分冗余，下面我們通過一段代碼來實現(xiàn)你想要一個視圖鋪滿它的父視圖。但是邊距為10.
UIView *superview = self;
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],
]
];
即使一個簡單的例子所需的代碼都相當(dāng)冗長，當(dāng)你有超過 2 或 3 視圖時變得不可讀，另一種選擇是使用可視化格式語言 (VFL)，有點不太冗長。然而，ASCII 類型語法上有它自己的陷阱并且作為 NSLayoutConstraint constraintsWithVisualFormat: 添加動畫效果 返回一個數(shù)組也有點難。
Masonry的優(yōu)點
下面是使用MASConstraintMaker創(chuàng)建同樣的約束
UIEdgeInsets padding = UIEdgeInsetsMake(10, 10, 10, 10);
[self.subview mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(self.view.mas_top).with.offset(padding.top);
make.left.equalTo(self.view.mas_left).with.offset(padding.left);
make.bottom.equalTo(self.view.mas_bottom).with.offset(-padding.bottom);
make.right.equalTo(self.view.mas_right).with.offset(-padding.right);
}];
更短代碼實現(xiàn)
[self.subview mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(self.view).with.insets(padding);
}];
此外還需注意使用NSLayoutConstraints時調(diào)用了[superview addConstraints:... ] 方法，在Masonry庫中是自動向當(dāng)前視圖添加約束的，我們也可以通過
self.subview.translatesAutoresizingMaskIntoConstraints = NO
來手動設(shè)置。
并不是所有創(chuàng)建都一樣
.equalTo 等價于 NSLayoutRelationEqual
.lessThanOrEqualTo 等價于 NSLayoutRelationLessThanOrEqual
.greaterThanOrEqualTo 等價于 NSLayoutRelationGreaterThanOrEqual
這些三個等式約束可以是下列任一操作作為一個參數(shù)
1. MASViewAttribute
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
-
UIView/NSView
如果你想要view.left大于或等于label.left可以make.left.greaterThanOrEqualTo(label); make.left.greaterThanOrEqualTo(label.mas_left); -
NSNumber
自動布局允許寬度和高度設(shè)置為常量值。如果你想要將視圖具有最小值和最大寬度設(shè)置你可以//width >= 200 && width <= 400 make.width.greaterThanOrEqualTo(@200); make.width.lessThanOrEqualTo(@400);
然而自動布局不允許對齊屬性如左對齊、 右對齊，centerY等將設(shè)置為常量值
//creates
view.left= view.superview.left + 10make.left.lessThanOrEqualTo(@10)
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));
您可以使用基元和結(jié)構(gòu)打造你的約束替代 NSNumber。默認情況下，支持自動裝箱的宏均以 mas_ 作為前綴。沒有前綴的版本均可通過導(dǎo)入之前定義 MAS_SHORTHAND_GLOBALS。
-
NSArray
make.height.equalTo(@[view1.mas_height, view2.mas_height]);make.height.equalTo(@[view1, view2]); make.left.equalTo(@[view1, @100, view3.right]);
優(yōu)先原則
.priority 允許你指定優(yōu)先級
.priorityHigh等價于 UILayoutPriorityDefaultHigh高優(yōu)先級
.priorityMedium 中等優(yōu)先級
.priorityLow 等價于 UILayoutPriorityDefaultLow
make.left.greaterThanOrEqualTo(label.mas_left).with.priorityLow();
make.top.equalTo(label.mas_top).with.priority(600);
組成
Masonry也提供了幾個方便的方法，同時創(chuàng)建多個約束，被稱為 MASCompositeConstraints。
edges
// make top, left, bottom, right equal view2make.edges.equalTo(view2);
// make top = superview.top + 5, left = superview.left + 10,
// bottom = superview.bottom - 15, right = superview.right - 20make.edges.equalTo(superview).insets(UIEdgeInsetsMake(5, 10, 15, 20))
center
// make centerX and centerY = button1make.center.equalTo(button1)
// make centerX = superview.centerX - 5, centerY = superview.centerY + 10make.center.equalTo(superview).centerOffset(CGPointMake(-5, 10))
// All edges but the top should equal those of the superviewmake.left.right.and.bottom.equalTo(superview);make.top.equalTo(otherView);