第三方框架Masonry的基本使用

1.Masonry支持的屬性

@property (nonatomic, strong, readonly) MASConstraint *left;
@property (nonatomic, strong, readonly) MASConstraint *top;
@property (nonatomic, strong, readonly) MASConstraint *right;
@property (nonatomic, strong, readonly) MASConstraint *bottom;
@property (nonatomic, strong, readonly) MASConstraint *leading;
@property (nonatomic, strong, readonly) MASConstraint *trailing;
@property (nonatomic, strong, readonly) MASConstraint *width;
@property (nonatomic, strong, readonly) MASConstraint *height;
@property (nonatomic, strong, readonly) MASConstraint *centerX;
@property (nonatomic, strong, readonly) MASConstraint *centerY;
@property (nonatomic, strong, readonly) MASConstraint *baseline;

這些屬性與NSLayoutAttrubute的對照表如下

2.通過一些簡單的實例來簡單介紹如何輕鬆愉快的使用Masonry:

在Masonry中能夠添加autolayout約束有三個函數

- (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block;
- (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block;
- (NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block;
/*
mas_makeConstraints 只負責新增約束 Autolayout不能同時存在兩條針對於同一對象的約束 否則會報錯 
mas_updateConstraints 針對上面的情況 會更新在block中出現的約束 不會導致出現兩個相同約束的情況
mas_remakeConstraints 則會清除之前的所有約束 僅保留最新的約束
三種函數善加利用 就可以應對各種情況了
*/

(1）居中顯示一個view

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
     
    WS(ws);
     
    UIView *sv = [UIView new];
    [sv showPlaceHolder];
    sv.backgroundColor = [UIColor blackColor];
    [self.view addSubview:sv];
    [sv mas_makeConstraints:^(MASConstraintMaker *make) {
        make.center.equalTo(ws.view);
        make.size.mas_equalTo(CGSizeMake(300, 300));
    }];
     
}

代碼效果

（2）讓一個view略小於其superView(邊距爲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));
     
    /* 等價於
    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);
    */
     
    /* 也等價於
    make.top.left.bottom.and.right.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10));
    */
}];

代碼效果

可以看到 edges 其實就是top,left,bottom,right的一個簡化 分開寫也可以 一句話更省事，注意and和with 其實這兩個函數什麼事情都沒做。

(3） 讓兩個高度爲150的view垂直居中且等寬且等間隔排列 間隔爲10(自動計算其寬度)

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);
}];

代碼效果