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，如果对VFL不是很熟悉可以参考 iOS开发-VFL(Visual format language)和Autolayout 。 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:

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: