PureLayout下載地址

https://github.com/PureLayout/PureLayout

PureLayout布局使用

    UIView *myview=[[UIView alloc]init];
    UILabel *label=[[UILabel alloc]init];
    UIButton *btn=[[UIButton alloc]init];
    myview.translatesAutoresizingMaskIntoConstraints=NO;
    label.translatesAutoresizingMaskIntoConstraints=NO;
    btn.translatesAutoresizingMaskIntoConstraints=NO;
    [self.view addSubview:myview];
    [self.view addSubview:label];
    [self.view addSubview:btn];

接下來我們就來看看purelayout封裝了哪些好用的布局方法：

 // myview左邊距離父視圖左邊 10 點.
    [myview autoPinEdgeToSuperviewEdge:ALEdgeLeading withInset:10.f];
    
    // myview1頂邊距離父視圖頂部 10 點.
    [myview autoPinEdgeToSuperviewEdge:ALEdgeTop withInset:10.f];
    
    // myview的左邊位于btn的右邊 10 點的地方.
    [myview autoPinEdge:ALEdgeLeading toEdge:ALEdgeTrailing ofView:btn withOffset:10.f];
    
    // myview的右邊位于btn左邊 -10 點的地方, 從右往左、從下往上布局時數(shù)值都是負的。
    [myview autoPinEdge:ALEdgeTrailing toEdge:ALEdgeLeading ofView:btn withOffset:-10.f];
    
    // 根據(jù)label的固有內(nèi)容尺寸設(shè)置它的尺寸
    [label autoSetDimensionsToSize:CGSizeMake(10.f, 10.f)];
    
    // myview、label、btn水平對齊。（意思就是說只需要設(shè)置其中一個的垂直約束（y）即可）（這個可以設(shè)置多個view水平對齊）
    [@[myview, label, btn] autoAlignViewsToAxis:ALAxisHorizontal];

    //myview，label水平對齊（這個是針對兩個view的水平對齊）
    [myview autoAlignAxis:ALAxisHorizontal toSameAxisOfView:label];
    
    // myview頂部距離label的底部 10 點.
    [myview autoPinEdge:ALEdgeTop toEdge:ALEdgeBottom ofView:label withOffset:10.f];
    
    // myview左邊緊貼父視圖左邊
    [myview autoPinEdgeToSuperviewEdge:ALEdgeLeading];
    
    // myview的寬度等于父視圖的寬度
    [myview autoMatchDimension:ALDimensionWidth toDimension:ALDimensionWidth ofView:self.view];
    
    // myview的寬度設(shè)置為50
    [myview autoSetDimension:ALDimensionWidth toSize:30];
    
    // myview與label左對齊
    [myview autoPinEdge:ALEdgeLeading toEdge:ALEdgeLeading ofView:label];
    
    // myview與label水平對齊
    [myview autoAlignAxis:ALAxisHorizontal toSameAxisOfView:label];
    
    //myview右邊雨label左邊的距離大于等于20
    [myview autoPinEdge:ALEdgeTrailing toEdge:ALEdgeLeading ofView:label withOffset:20.f relation:NSLayoutRelationGreaterThanOrEqual];

    //myview和btn同寬(同高也一樣)
    [@[myview,btn] autoMatchViewsDimension:ALDimensionWidth];//這種可以設(shè)置多個view同寬
    [myview autoMatchDimension:ALDimensionWidth toDimension:ALDimensionWidth ofView:btn];//這種只能設(shè)置兩個view同寬

注意：這里我主要講一下NSLayoutAttributeLeft ,NSLayoutAttributeRight,和NSLayoutAttributeLeading,NSLayoutAttributeTrailing之間的區(qū)別。
其實在中國， NSLayoutAttributeLeft 和 NSLayoutAttributeLeading 是一個效果的，因為我們布局習慣從左到右。但在有些國家地區(qū)，NSLayoutAttributeRight和NSLayoutAttributeLeading 是一個效果，布局習慣從右往左。這點我們大可放心，建議大家還是使用NSLayoutAttributeLeading,NSLayoutAttributeTrailing來表示左和右。

PureLayout更改約束

我們點擊它的方法進去先看一下：

- (NSLayoutConstraint *)autoAlignAxisToSuperviewMarginAxis:(ALAxis)axis
{
    self.translatesAutoresizingMaskIntoConstraints = NO;
    ALView *superview = self.superview;
    NSAssert(superview, @"View's superview must not be nil.\nView: %@", self);
    ALMarginAxis marginAxis = [NSLayoutConstraint al_marginAxisForAxis:axis];
    return [self autoConstrainAttribute:(ALAttribute)axis toAttribute:(ALAttribute)marginAxis ofView:superview];
}

#endif /* __PureLayout_MinBaseSDK_iOS_8_0 */


#pragma mark Pin Edges to Superview

/**
 Pins the given edge of the view to the same edge of its superview.
 
 @param edge The edge of this view and its superview to pin.
 @return The constraint added.
 */
- (NSLayoutConstraint *)autoPinEdgeToSuperviewEdge:(ALEdge)edge
{
    return [self autoPinEdgeToSuperviewEdge:edge withInset:0.0];
}

/**
 Pins the given edge of the view to the same edge of its superview with an inset.
 
 @param edge The edge of this view and its superview to pin.
 @param inset The amount to inset this view's edge from the superview's edge.
 @return The constraint added.
 */
- (NSLayoutConstraint *)autoPinEdgeToSuperviewEdge:(ALEdge)edge withInset:(CGFloat)inset
{
    return [self autoPinEdgeToSuperviewEdge:edge withInset:inset relation:NSLayoutRelationEqual];
}

發(fā)現(xiàn)這些方法都會返回一個NSLayoutConstraint。那么更新就好辦了

//首先定義好一個NSLayoutConstraint屬性
@property (nonatomic, strong)NSLayoutConstraint *myyueshu;
//如果我們點擊按鈕需要更改某個view的高度從100到200
    UIView *myview = [[UIView alloc]init];
    self.myview = myview;
    [self.view addSubview:myview];
    myview.backgroundColor = [UIColor redColor];
    [self.view addSubview:myview];
    myview.translatesAutoresizingMaskIntoConstraints = NO;
    [myview autoPinEdgeToSuperviewEdge:ALEdgeLeading];
    [myview autoPinEdgeToSuperviewEdge:ALEdgeTrailing];
    [myview autoPinEdgeToSuperviewEdge:ALEdgeTop];
//    [myview autoSetDimension:ALDimensionHeight toSize:100];
    self.myyueshu =  [myview autoSetDimension:ALDimensionHeight toSize:100];

    UIButton *btn = [[UIButton alloc]init];
    [self.view addSubview:btn];
    btn.frame = CGRectMake(10, 400, 40, 40);
    btn.backgroundColor = [UIColor redColor];
    [btn addTarget:self action:@selector(btnclick) forControlEvents:UIControlEventTouchUpInside];

把設(shè)置高度從原先的100變?yōu)?00，我們直接改變了它的約束數(shù)值

- (void)btnclick{
    self.myyueshu.constant = 200;
    
}

或者先把原先的那個約束移除，然后重新添加新的約束。

- (void)btnclick{
    
    [self.myyueshu autoRemove];
    self.myyueshu = [self.myview autoSetDimension:ALDimensionHeight toSize:200];
}

如果我們需要把所有約束都重寫，以上代碼也可以做到，只是要定義4個約束屬性，然后各個移除而已。當然我們也可以用別的方法

//首先定義好一個數(shù)組NSArray
@property (nonatomic, strong) NSArray *contentConstrains;
//接著在viewDidLoad中實現(xiàn)以下代碼：
    UIView *myview = [[UIView alloc]init];
    self.myview = myview;
    [self.view addSubview:myview];
    myview.backgroundColor = [UIColor redColor];
    [self.view addSubview:myview];
    myview.translatesAutoresizingMaskIntoConstraints = NO;
    NSLayoutConstraint *s1 = [myview autoPinEdgeToSuperviewEdge:ALEdgeLeading];
    NSLayoutConstraint *s2 = [myview autoPinEdgeToSuperviewEdge:ALEdgeTrailing];
    NSLayoutConstraint *s3 = [myview autoPinEdgeToSuperviewEdge:ALEdgeTop];
    NSLayoutConstraint *s4 = [myview autoSetDimension:ALDimensionHeight toSize:100];
    self.contentConstrains = [NSArray arrayWithObjects:s1,s2,s3,s4, nil];
    
    UIButton *btn = [[UIButton alloc]init];
    [self.view addSubview:btn];
    btn.frame = CGRectMake(10, 400, 40, 40);
    btn.backgroundColor = [UIColor redColor];
    [btn addTarget:self action:@selector(btnclick) forControlEvents:UIControlEventTouchUpInside];

這樣也可以實現(xiàn)整體更改約束。

- (void)btnclick{
    
    if(self.contentConstrains != nil){
        [self.contentConstrains autoRemoveConstraints];
    }
    
    [self.myview autoPinEdgeToSuperviewEdge:ALEdgeLeading];
    [self.myview autoPinEdgeToSuperviewEdge:ALEdgeTrailing];
    [self.myview autoPinEdgeToSuperviewEdge:ALEdgeTop withInset:30];
    [self.myview autoSetDimension:ALDimensionHeight toSize:200];
   
}