问iOS 7.1幻灯片可解锁文本动画

EN

CALayer *maskLayer = [CALayer layer];
// Mask image ends with 0.15 opacity on both sides. Set the background color of the         layer
// to the same value so the layer can extend the mask image.
maskLayer.backgroundColor = [[UIColor colorWithRed:0.0f green:0.0f blue:0.0f  alpha:0.15f] CGColor];
maskLayer.contents = (id)[[UIImage imageNamed:@"Mask.png"] CGImage];

// Center the mask image on twice the width of the text layer, so it starts to the left
// of the text layer and moves to its right when we translate it by width.
maskLayer.contentsGravity = kCAGravityCenter;
maskLayer.frame = CGRectMake(myLabel.frame.size.width * -1, 0.0f,   myLabel.frame.size.width * 2, myLabel.frame.size.height);
// Animate the mask layer's horizontal position
CABasicAnimation *maskAnim = [CABasicAnimation animationWithKeyPath:@"position.x"];
maskAnim.byValue = [NSNumber numberWithFloat:myLabel.frame.size.width];
maskAnim.repeatCount = 1e100f;
maskAnim.duration = 1.5f;
[maskLayer addAnimation:maskAnim forKey:@"slideAnim"];
myLabel.layer.mask = maskLayer;