Masonry布局约束的UIView动画使用方法

在没有自动布局之前我们都是用Frame去布局view，然后可以对view 做各种动画

• 大小变化(frame)
• 拉伸变化(bounds)
• 中心位置(center)
• 旋转(transform)
• 透明度(alpha)
• 背景颜色(backgroundColor)
• 拉伸内容(contentStretch)

但是有了自动布局之后，之前的方法稍微有所不同, 具体实现如下：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    UIView *tview = [[UIView alloc] init];
    tview.backgroundColor = [UIColor redColor];
    [self.view addSubview:tview];
    
    [tview mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(tview.superview).offset(200);
        make.left.equalTo(tview.superview).offset(50);
        make.right.equalTo(tview.superview).offset(-100);
        make.height.equalTo(80);
    }];

    self.testView = tview;
    
    [self performSelector:@selector(startAnimation) withObject:nil afterDelay:1];
}


- (void)startAnimation{
    //重点
    [self.testView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.testView.superview).offset(300);
    }];

    [UIView animateWithDuration:0.66 delay:0.0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
         //重点
        [self.testView.superview layoutIfNeeded];
    } completion:^(BOOL finished) {
        
    }];
}

从最终效果来看好像没有什么问题，但是注意我们对top用了mas_updateConstraints，但是没有uninstall，这样的话有时候会有约束冲突，保险的是先[self.testViewTop uninstall]，然后mas_updateConstraints，具体实现如下：

@property (nonatomic, strong) MASConstraint *testViewTopConst;

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    UIView *tview = [[UIView alloc] init];
    tview.backgroundColor = [UIColor redColor];
    [self.view addSubview:tview];
    
    [tview mas_makeConstraints:^(MASConstraintMaker *make) {
        self.testViewTopConst = make.top.equalTo(tview.superview).offset(200);//重点
        make.left.equalTo(tview.superview).offset(50);
        make.right.equalTo(tview.superview).offset(-100);
        make.height.equalTo(80);
    }];

    self.testView = tview;
    
    [self performSelector:@selector(startAnimation) withObject:nil afterDelay:1];
}


- (void)startAnimation{
    [self.testViewTopConst uninstall];//重点
    [self.testView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.testView.superview).offset(300);
    }];

    [UIView animateWithDuration:0.66 delay:0.0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        [self.testView.superview layoutIfNeeded];
    } completion:^(BOOL finished) {
        
    }];
}

除过这个方法还有一种更简单，安全的，就是我们把我们需要改变的约束用系统的NSLayoutConstraint来添加约束，最终只要修改constant值就行，具体如下：

@property (nonatomic, strong) NSLayoutConstraint *topConst;//重点

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    UIView *tview = [[UIView alloc] init];
    tview.backgroundColor = [UIColor redColor];
    [self.view addSubview:tview];
    
    [tview mas_makeConstraints:^(MASConstraintMaker *make) {
        //make.top.equalTo(tview.superview).offset(200);
        make.left.equalTo(tview.superview).offset(50);
        make.right.equalTo(tview.superview).offset(-100);
        make.height.equalTo(80);
    }];
    
    
    NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:tview
                                                                     attribute:NSLayoutAttributeTop
                                                                     relatedBy:NSLayoutRelationEqual
                                                                        toItem:tview.superview
                                                                     attribute:NSLayoutAttributeTop
                                                                    multiplier:1
                                                                      constant:50];


    
    [self.view addConstraint:topConstraint];//重点
    self.topConst = topConstraint;//重点
    
    self.testView = tview;
    
    [self performSelector:@selector(startAnimation) withObject:nil afterDelay:1];
}


- (void)startAnimation{
    self.topConst.constant = 300;//重点
    [UIView animateWithDuration:0.66 delay:0.0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        [self.testView.superview layoutIfNeeded];
    } completion:^(BOOL finished) {
        
    }];
}

总结：

• 方法一：直接用 mas_updateConstraints
• 方法二：先uninstall，然后mas_updateConstraints
• 方法三； 用系统的NSLayoutConstraint添加约束，然后修改constant值。

建议使用第三种简单，安全