Masonry 布局

转自：http://www.cocoachina.com/ios/20141219/10702.html 用作笔记，多谢作者！么么哒

1418956465427751.jpg

提供的方法：
//新增约束

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

//更新约束

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

//清楚之前的所有约束,只会保留最新的约束

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

合理的利用这个3个函数，基本上可以应对任何情况了

下面这些是基本的设置属性
**
1.尺寸：width、height、size
2.边界：left、leading、right、trailing、top、bottom
3.中心点：center、centerX、centerY
4.边界：edges
5.偏移量：offset、insets、sizeOffset、centerOffset
6.priority()约束优先级（0~1000），multipler乘因数, dividedBy除因数
*/

有三种关系：等于，小于，大于
.equalTo
.lessThanOrEqualTo
.greaterThanOrEqualTo

示例代码：
//从此以后基本可以抛弃CGRectMake了
UIView *sv = [UIView new];
//在做autoLayout之前 一定要先将view添加到superview上 否则会报错
[self.view addSubview:sv];
//mas_makeConstraints就是Masonry的autolayout添加函数 将所需的约束添加到block中行了
[sv mas_makeConstraints:^(MASConstraintMaker *make) {
//将sv居中(很容易理解吧?)
make.center.equalTo(ws.view);

//将size设置成(300,300)
make.size.mas_equalTo(CGSizeMake(300, 300));

}];

[初级] 让一个view略小于其superView(边距为10)

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));
*/

}];
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

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);
}];

[中级] 在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);
}];