关于ios布局自动iphone6之后就是autolayout，autolayout固然非常好用，不过有时候我们需要在页面手动进行页面布局，vfl算是一种选择，而且vfl不复杂，理解起来很容易，实际开发中用的特别熟还好，要是第一次看估计要花点功夫才能搞定。masonry算是vfl的简化版，用的人比较多，之前项目中用过一次，对手动写页面的开发来说算是福利。
基础知识
首先我们看一个常见的问题将一个子view放在的uiviewcontroller的某个位置，通过设置边距来实现，效果如下:
如果通过vfl我们代码会是这样的:
uiview *superview = self.view; uiview *view1 = [[uiview alloc] init]; view1.translatesautoresizingmaskintoconstraints = no; view1.backgroundcolor = [uicolor redcolor]; [superview addsubview:view1]; uiedgeinsets padding = uiedgeinsetsmake(200, 50, 200, 50); [superview addconstraints:@[ //约束 [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], ]];
只是简单的设置了一个边距，如果视图的关系比较复杂，维护起来会是一个很痛苦的事情，我们看一下masonry是如何实现的，导入masonry.h头文件，约束的代码:
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uiview *childview=[uiview new];
[childview setbackgroundcolor:[uicolor redcolor]];
//先将子view加入在父视图中
[self.view addsubview:childview];
__weak typeof(self) weakself = self;
uiedgeinsets padding = uiedgeinsetsmake(200, 50, 200, 50);
[childview mas_makeconstraints:^(masconstraintmaker *make) {
make.edges.equalto(weakself.view).with.insets(padding);
}];
通过mas_makeconstraints设置边距有种鸟枪换炮的感觉，我们即将开启一段新的旅程，可以紧接着看下面比较实用的功能~
实用知识
1.view设置大小
uiview *childview=[uiview new];
[childview setbackgroundcolor:[uicolor redcolor]];
//先将子view加入在父视图中
[self.view addsubview:childview];
__weak typeof(self) weakself = self;
[childview mas_makeconstraints:^(masconstraintmaker *make) {
//设置大小
make.size.mas_equalto(cgsizemake(100, 100));
//居中
make.center.equalto(weakself.view);
}];
效果如下:
这里友情其实一个小内容，目前我们设置约束都是通过mas_makeconstraints用来创建约束,mas_updateconstraints用来更新约束，mas_remakeconstraints重置约束，清除之前的约束，保留最新的约束,如果想深入解释下，可以阅读下面的英文解释~
/** * creates a masconstraintmaker with the callee view. * any constraints defined are added to the view or the appropriate superview once the block has finished executing * * @param block scope within which you can build up the constraints which you wish to apply to the view. * * @return array of created masconstraints */ - (nsarray *)mas_makeconstraints:(void(^)(masconstraintmaker *make))block; /** * creates a masconstraintmaker with the callee view. * any constraints defined are added to the view or the appropriate superview once the block has finished executing. * if an existing constraint exists then it will be updated instead. * * @param block scope within which you can build up the constraints which you wish to apply to the view. * * @return array of created/updated masconstraints */ - (nsarray *)mas_updateconstraints:(void(^)(masconstraintmaker *make))block; /** * creates a masconstraintmaker with the callee view. * any constraints defined are added to the view or the appropriate superview once the block has finished executing. * all constraints previously installed for the view will be removed. * * @param block scope within which you can build up the constraints which you wish to apply to the view. * * @return array of created/updated masconstraints */ - (nsarray *)mas_remakeconstraints:(void(^)(masconstraintmaker *make))block;
2.设置高度，这里设置左右边距，因此不设置宽度，如果想单独设置width可参考高度的设置方式:
uiview *childview=[uiview new];
[childview setbackgroundcolor:[uicolor greencolor]];
//先将子view加入在父视图中
[self.view addsubview:childview];
__weak typeof(self) weakself = self;
[childview mas_makeconstraints:^(masconstraintmaker *make) {
//距离顶部44
make.top.equalto(weakself.view.mas_top).with.offset(44);
//距离左边30
make.left.equalto(weakself.view.mas_left).with.offset(30);
//距离右边30，注意是负数
make.right.equalto(weakself.view.mas_right).with.offset(-30);
//高度150
make.height.mas_equalto(@150);
}];
3.子视图之间的位置设置:
uiview *childview=[uiview new];
[childview setbackgroundcolor:[uicolor greencolor]];
//先将子view加入在父视图中
[self.view addsubview:childview];
__weak typeof(self) weakself = self;
[childview mas_makeconstraints:^(masconstraintmaker *make) {
//距离顶部44
make.top.equalto(weakself.view.mas_top).with.offset(44);
//距离左边30
make.left.equalto(weakself.view.mas_left).with.offset(30);
//距离右边30，注意是负数
make.right.equalto(weakself.view.mas_right).with.offset(-30);
//高度150
make.height.mas_equalto(@150);
}];
//地址:http://www.cnblogs.com/xiaofeixiang/
uiview *nextview=[uiview new];
[nextview setbackgroundcolor:[uicolor redcolor]];
[self.view addsubview:nextview];
[nextview mas_makeconstraints:^(masconstraintmaker *make) {
make.top.equalto(childview.mas_bottom).with.offset(30);
make.right.equalto(childview.mas_right).with.offset(-30);
make.width.mas_equalto(@100);
make.height.mas_equalto(@100);
}];
4.链式写法，算是一个便利的写法:
uiview *childview=[uiview new];
[childview setbackgroundcolor:[uicolor greencolor]];
//先将子view加入在父视图中
[self.view addsubview:childview];
__weak typeof(self) weakself = self;
[childview mas_makeconstraints:^(masconstraintmaker *make) {
make.top.and.left.mas_equalto(weakself.view).with.offset(100);
make.bottom.and.right.mas_equalto(weakself.view).with.offset(-100);
//第二种写法更简单，相对于就是父视图
// make.top.and.left.mas_equalto(100);
// make.bottom.and.right.mas_equalto(-100);
}];
uilabel *label=[uilabel new];
[label settext:@"博客园-flyelephant"];
[label settextcolor:[uicolor redcolor]];
[label settextalignment:nstextalignmentcenter];
[self.view addsubview:label];
[label mas_makeconstraints:^(masconstraintmaker *make) {
make.left.mas_equalto(weakself.view).with.offset(10);
make.height.mas_equalto(20);
make.right.mas_equalto(weakself.view).with.offset(-10);
make.bottom.mas_equalto(weakself.view).with.offset(-50);
}];
网上关于masonry的教程很多，给的例子的也很多，这几种情况基本上满足了开发中的需求，不会有太多的出入，算是一个简易版的教程，masonry的中属性和ios中的属性是有对应的关系，不过因为很简单，基本上没怎么看，下图是一个对照关系:
总结：
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