Sliding Animation of UILabel like "Telop" or news texts on Social Game 　スライドインするテロップ的なアニメーション

animationOnTelop

- (void)viewDidLoad
{
    _newsLabel.text = @"abcdefgh.......";
    [self startSlideNewsAnimation];
}

- (void)startSlideNewsAnimation
{
    NSString *news = _newsLabel.text;
    
    UIFont *font = [UIFont boldSystemFontOfSize:FONT_SIZE_L];
    NSDictionary *attribute = @{NSFontAttributeName:font};
    CGSize size;
    if([SNUtil osVersion]>=7.0f){
        size = [news boundingRectWithSize:CGSizeMake(640, 20)
                                  options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                               attributes:attribute
                                  context:nil].size;
    }else{
        size = [news sizeWithFont:font constrainedToSize:CGSizeMake(640.0, 20.0) lineBreakMode:NSLineBreakByWordWrapping];
    }
    
    CGRect newRect = _newsLabel.frame;
    newRect.size.width = size.width;
    _newsLabel.frame = newRect;
    
    
    static int MAX_LENGTH = 17;
    static float SEC_PER_CHAR = 0.9f;
    
    CGFloat sec = news.length * SEC_PER_CHAR;
    if(sec < MAX_LENGTH*SEC_PER_CHAR){
        sec = MAX_LENGTH*SEC_PER_CHAR;
    }
    
    [UIView animateWithDuration:sec
                          delay:0.5f
                        options:UIViewAnimationOptionCurveLinear
                     animations:^{
                         CGRect frame = _newsLabel.frame;
                         frame.origin.x = frame.origin.x - frame.size.width;
                         _newsLabel.frame = frame;
                     } completion:^(BOOL finished) {
                         [self startSlideNewsToStartPointAnimation];
                         
                     }];
}


- (void)startSlideNewsToStartPointAnimation
{
    CGRect newRect = _newsLabel.frame;
    newRect.origin.x = 320;
    _newsLabel.frame = newRect;
    
    [UIView animateWithDuration:0.8f
                          delay:0.0f
                        options:UIViewAnimationOptionCurveLinear
                     animations:^{
                         CGRect frame = _newsLabel.frame;
                         frame.origin.x = 128.0f;
                         _newsLabel.frame = frame;
                     } completion:^(BOOL finished) {
                         DEBUGLOG(@"second-slide Complete!!");
                         [self startSlideNewsAnimation];
                     }];
}