AutoLayout-代码布局添加动画

    开始之前先推荐老外封装好的开源库Masonry，Masonry是一个轻量级的布局框架,拥有自己的描述语法,简洁明了并具有高可读性。下面得例子用系统API实现一个和Masonry一样得布局，点击一个Button改变尺寸，Button尺寸不能超过VC界面；

添加一个button在VC中心

@interface PPBUpdateVC()
@property (nonatomic,strong) UIButton *growingButton;
@property (nonatomic,strong) NSLayoutConstraint *layoutWith;
@property (nonatomic,strong) NSLayoutConstraint *layoutHeight;
@end

添加button

self.growingButton = [UIButton buttonWithType:UIButtonTypeSystem];
    [self.growingButton setTitle:@"Grow Me!" forState:UIControlStateNormal];
    self.growingButton.layer.borderColor = UIColor.greenColor.CGColor;
    self.growingButton.layer.borderWidth = 3;
    self.growingButton.translatesAutoresizingMaskIntoConstraints = NO;
    [self.growingButton addTarget:self action:@selector(didTapGrowButton:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.growingButton];

添加宽度约束

self.layoutWith = [NSLayoutConstraint
                       constraintWithItem:self.growingButton
                       attribute:NSLayoutAttributeWidth
                       relatedBy:NSLayoutRelationEqual
                       toItem:nil
                       attribute:NSLayoutAttributeNotAnAttribute
                       multiplier:1.0
                       constant:100];
    self.layoutWith.priority = UILayoutPriorityDefaultHigh;
    [self.growingButton addConstraint:self.layoutWith];  

添加高度约束

self.layoutHeight = [NSLayoutConstraint
                       constraintWithItem:self.growingButton
                       attribute:NSLayoutAttributeHeight
                       relatedBy:NSLayoutRelationEqual
                       toItem:nil
                       attribute:NSLayoutAttributeNotAnAttribute
                       multiplier:1.0
                       constant:100];
    self.layoutHeight.priority = UILayoutPriorityDefaultHigh;
    [self.growingButton addConstraint:self.layoutHeight];

添加中心点约束

NSLayoutConstraint *centerX = [NSLayoutConstraint constraintWithItem:self.growingButton attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0];
    NSLayoutConstraint *centerY = [NSLayoutConstraint constraintWithItem:self.growingButton attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0];
    [self.view addConstraint:centerX];
    [self.view addConstraint:centerY];

添加button的最大宽度和高度，这里要注意的是，对同一个属性添加多个约束要设置优先级，否则会报错。

self.layoutWith.priority = UILayoutPriorityDefaultHigh;

NSLayoutConstraint *maxWidth = [NSLayoutConstraint constraintWithItem:self.growingButton
                                 attribute:NSLayoutAttributeWidth
                                 relatedBy:NSLayoutRelationLessThanOrEqual
                                    toItem:self.view
                                 attribute:NSLayoutAttributeWidth
                                multiplier:1.0
                                  constant:0];
    [self.view addConstraint:maxWidth];
    
    [self.view addConstraint:
     [NSLayoutConstraint constraintWithItem:self.growingButton
                                  attribute:NSLayoutAttributeHeight
                                  relatedBy:NSLayoutRelationLessThanOrEqual
                                     toItem:self.view
                                  attribute:NSLayoutAttributeHeight
                                 multiplier:1.0 constant:0]];

}

button点击事件

- (void)didTapGrowButton:(UIButton *)button {
    self.layoutHeight.constant = self.layoutHeight.constant * 1.3;
    self.layoutWith.constant   = self.layoutWith.constant * 1.3;
    [UIView animateWithDuration:0.4 animations:^{
        [self.growingButton layoutIfNeeded];
    }];
}

附源代码  https://github.com/p-p-b/AutoLayoutDemo    

来源：oschina

链接：https://my.oschina.net/u/2312766/blog/418978