iPhone “slide to unlock” animation

Question

Any ideas as to how Apple implemented the \"slide to unlock\" (also, \"slide to power off\" is another identical example) animation?

I thought about some sort of ani

Answer 1

I took the best from above solutions and created a neat method that does all for you:

- (void)createSlideToUnlockViewWithText:(NSString *)text
{
    UILabel *label = [[UILabel alloc] init];
    label.text = text;
    [label sizeToFit];
    label.textColor = [UIColor whiteColor];

    //Create an image from the label
    UIGraphicsBeginImageContextWithOptions(label.bounds.size, NO, 0.0);
    [[label layer] renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *textImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    CGFloat textWidth = textImage.size.width;
    CGFloat textHeight = textImage.size.height;

    CALayer *textLayer = [CALayer layer];
    textLayer.contents = (id)[textImage CGImage];
    textLayer.frame = CGRectMake(self.view.frame.size.width / 2 - textWidth / 2, self.view.frame.size.height / 2 - textHeight / 2, textWidth, textHeight);

    UIImage *maskImage = [UIImage imageNamed:@"Mask.png"];
    CALayer *maskLayer = [CALayer layer];
    maskLayer.backgroundColor = [[UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.15] CGColor];
    maskLayer.contents = (id)maskImage.CGImage;
    maskLayer.contentsGravity = kCAGravityCenter;
    maskLayer.frame = CGRectMake(-textWidth - maskImage.size.width, 0.0, (textWidth * 2) + maskImage.size.width, textHeight);

    CABasicAnimation *maskAnimation = [CABasicAnimation animationWithKeyPath:@"position.x"];
    maskAnimation.byValue = [NSNumber numberWithFloat:textWidth + maskImage.size.width];
    maskAnimation.repeatCount = HUGE_VALF;
    maskAnimation.duration = 2.0;
    maskAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    [maskLayer addAnimation:maskAnimation forKey:@"slideAnimation"];

    textLayer.mask = maskLayer;
    self.slideToUnlockLayer = textLayer;
    [self.view.layer addSublayer:self.slideToUnlockLayer];
}