xib中控件的动画的添加

@property (nonatomic,strong) MASConstraint *topConstraint; // 创建view1居上距离属性
@property (nonatomic,strong) UIView *view1;

self.view1 = [[UIView alloc] init];
    self.view1.translatesAutoresizingMaskIntoConstraints = NO; // 要先赋值为NO
    self.view1.backgroundColor = [UIColor greenColor];
#pragma mark 注：要使用autoLayout，必须先将页面addSubview，否则报错
    [self.view addSubview:self.view1];

// 屏宽、高30、居父类左0上10
    [self.view1 mas_makeConstraints:^(MASConstraintMaker *make) {
        make.width.equalTo(self.view1.superview.mas_width);
        make.height.equalTo(@30);
        make.left.equalTo(self.view1.superview.mas_left).with.offset(0);
        // view1居上距离属性赋值
        self.topConstraint = make.top.equalTo(self.view1.superview.mas_top).with.offset(50);
    }];

#pragma mark 点击按钮，执行动画
- (void)buttonClick:(UIButton *)sender {

    [UIView animateWithDuration:2 animations:^{
        self.topConstraint.offset = 100; // 从新设置view1的居上的偏移量，使其等于100
        [self.view layoutIfNeeded]; // 只有添加了这个方法，才能有动画
    }];
}