IOS学习 autolayout 动画 与文件夹拖拽截图

@interface ViewController ()

@property (weak,nonatomic) IBOutletUIView *redView;

@property (weak,nonatomic) IBOutletNSLayoutConstraint *redTop; //绑定约束

@end

@implementation ViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

    //只是修改约束

    self.redTop.constant +=50;

    [UIViewanimateWithDuration:0.5animations:^{

        //调用这个方法，可以刷新View上所有约束

        [self.viewlayoutIfNeeded];

    }];

}