iOS使用约束实现动画效果

我知道的方法有两种&＃xff1a;

1.在改变完约束后&＃xff0c;在动画块内&＃xff0c;使用方法layoutIfNeeded&＃xff0c;可以实现一般普通的动画效果。

2.使用Facebook的pop框架&＃xff0c;给约束加动画&＃xff0c;实例代码如下&＃xff08;pop详情见&＃xff1a;http://www.jianshu.com/p/1172578c96e1&＃xff09;。

#import "ViewController.h"

#import "Masonry.h"

#import "POP.h"

&＃64;interface ViewController ()

/*!*/

&＃64;property (nonatomic,strong) UILabel *label;

&＃64;end

&＃64;implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

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

    [self label];

}

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

    [super touchesEnded:touches withEvent:event];

    NSLayoutConstraint *leftConstraint &＃61; nil;

//    POPSpringAnimation *positionAnimation &＃61; [POPSpringAnimation animationWithPropertyNamed:kPOPLayoutConstraintConstant];//kPOPLayerPositionY

    POPBasicAnimation *positionAnimation &＃61; [POPBasicAnimation animationWithPropertyNamed:kPOPLayoutConstraintConstant];

    for (NSLayoutConstraint *constraint in self.view.constraints) {

        if (constraint.firstItem &＃61;&＃61; self.label && constraint.firstAttribute &＃61;&＃61; NSLayoutAttributeLeft) {

            leftConstraint &＃61; constraint;

            break;

        }

    }

    positionAnimation.duration &＃61; 1;

    positionAnimation.fromValue &＃61; &＃64;(leftConstraint.constant);

    positionAnimation.toValue &＃61; &＃64;(0);

//    positionAnimation.springBounciness &＃61; 10;

    [positionAnimation setCompletionBlock:^(POPAnimation *anim, BOOL finished) {

        [_label mas_updateConstraints:^(MASConstraintMaker *make) {

            make.left.equalTo(self.view).offset(100);

        }];

    }];

    [leftConstraint pop_addAnimation:positionAnimation forKey:&＃64;"constantAnimation"];

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

#pragma mark - Getter

- (UILabel *)label {

    if (! _label) {

        _label &＃61; [[UILabel alloc]init];

        _label.backgroundColor &＃61; [UIColor cyanColor];

        _label.text &＃61; &＃64;"what test123";

        [self.view addSubview:_label];

        [_label mas_makeConstraints:^(MASConstraintMaker *make) {

            make.left.equalTo(self.view).offset(300);

            make.top.equalTo(self.view).offset(100);

        }];

    }

    return _label;

}

&＃64;end