AutoLayout-代碼佈局添加動畫

    開始以前先推薦老外封裝好的開源庫Masonry，Masonry是一個輕量級的佈局框架,擁有本身的描述語法,簡潔明瞭並具備高可讀性。下面得例子用系統API實現一個和Masonry同樣得佈局，點擊一個Button改變尺寸，Button尺寸不能超過VC界面；

添加一個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];

添加寬度約束

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];  

添加高度約束

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];

添加中心點約束

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的最大寬度和高度，這裏要注意的是，對同一個屬性添加多個約束要設置優先級，不然會報錯。

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點擊事件

- (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];
    }];
}

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