在 iOS 中使用 Objective C 对 UlLabel 帧周围的边框进行动画处理

Question

我正在使用Objective C开发iPhone应用程序，我需要为UILabel制作边框动画。

我尝试了以下代码使用CABasicAnimation：

CABasicAnimation* borderAnimation = [CABasicAnimation animationWithKeyPath:@"borderWidth"];
[borderAnimation setFromValue:[NSNumber numberWithFloat:4.0f]];
[borderAnimation setToValue:[NSNumber numberWithFloat:0.0f]];
[borderAnimation setRepeatCount:1.0];
[borderAnimation setAutoreverses:NO];
[borderAnimation setDuration:0.7f];
[focusScannerView.layer addAnimation:borderAnimation forKey:@"animateBorder"];

但是边框动画并不完美。有人知道我会怎么做吗？提前谢谢你。

Answer 1

#import "ViewController.h"
@interface ViewController ()
{
UIBezierPath *path;
CAShapeLayer *shapeLayer;
int lineNo;
}
@property (nonatomic, weak) IBOutlet UILabel *textLabel;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
path = [UIBezierPath bezierPath];
shapeLayer = [CAShapeLayer layer];
shapeLayer.strokeColor = [[UIColor blueColor] CGColor];
shapeLayer.lineWidth = 3.0;
shapeLayer.fillColor = [[UIColor clearColor] CGColor];
[_textLabel addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(startAnimation)]];
// Do any additional setup after loading the view, typically from a nib.
}
-(void)startAnimation{
lineNo = 0;
[self drawLine:lineNo];
}
-(void)drawLine:(int)line{
CGPoint startPoint;
CGPoint endPoint;
switch (line) {
case 0:
startPoint = CGPointMake(self.textLabel.frame.origin.x, self.textLabel.frame.origin.y);
endPoint = CGPointMake(CGRectGetMaxX(self.textLabel.frame), self.textLabel.frame.origin.y);
break;
case 1:
startPoint = CGPointMake(CGRectGetMaxX(self.textLabel.frame), self.textLabel.frame.origin.y);
endPoint = CGPointMake(CGRectGetMaxX(self.textLabel.frame), CGRectGetMaxY(self.textLabel.frame));
break;
case 2:
startPoint = CGPointMake(CGRectGetMaxX(self.textLabel.frame), CGRectGetMaxY(self.textLabel.frame));
endPoint = CGPointMake(self.textLabel.frame.origin.x, CGRectGetMaxY(self.textLabel.frame));
break;
case 3:
startPoint = CGPointMake(self.textLabel.frame.origin.x, CGRectGetMaxY(self.textLabel.frame));
endPoint = CGPointMake(self.textLabel.frame.origin.x, self.textLabel.frame.origin.y);
break;
default:
return;
}
[self animateStartPoint:startPoint andEndPoint:endPoint];
}
-(void)animateStartPoint:(CGPoint) startPoint andEndPoint:(CGPoint)endPoint{
[path moveToPoint:startPoint];
[path addLineToPoint:endPoint];
shapeLayer.path = [path CGPath];
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
animation.duration = 5;
animation.removedOnCompletion = NO;
animation.fromValue = @(0);
animation.toValue = @(1);
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
[shapeLayer addAnimation:animation forKey:@"drawLineAnimation"];
[self.view.layer addSublayer:shapeLayer];
lineNo++;
[self drawLine:lineNo];
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end