IOS自适配利器Masonry使用指南

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:

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：

1. 可以给控件添加left/right/top/bottom/size/height/width/insert约束；
2. 库提供了三个方法，mas_makeconstraints添加约束，mas_updateconstraints修改约束，mas_remakeconstraints清除以前约束并添加新约束；
3. 可以通过view.mas_bottom获得view的某个约束；
4. 在约束的block中，使用make来给当前控件添加约束。