UILabel: multiple lines of text animation fade line by line - ios

Question

for example:
label.text = #"I \n love \n stackoverflow ";
how to show those three lines just like first animation fade show "I" , then after animation during time animation fade show "love" finally after animation during time animation fade show "stackoverflow"?

Answer 1

I have created a function for your request. Make sure your label have dynamic height, numberOfLines = 0 and try it ;)
- (void)animateLabel:(UILabel*)label withString:(NSString*)string duration:(NSTimeInterval)duration {
NSUInteger length = [string length];
NSUInteger paraStart = 0, paraEnd = 0, contentsEnd = 0;
NSMutableArray *displayedStringArray = [NSMutableArray array];
NSRange currentRange;
while (paraEnd < length) {
[string getParagraphStart:&paraStart end:&paraEnd
contentsEnd:&contentsEnd forRange:NSMakeRange(paraEnd, 0)];
currentRange = NSMakeRange(0, contentsEnd);
[displayedStringArray addObject:[string substringWithRange:currentRange]];
}
CATransition *animation = [CATransition animation];
animation.duration = duration;
animation.type = kCATransitionFade;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
__block void (^animationBlock) (int lineNumber);
__block void (^weakAnimationBlock) (int lineNumber);
animationBlock = ^void(int lineNumber){
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(duration * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[label.layer addAnimation:animation forKey:#"changeTextTransition"];
label.text = displayedStringArray[lineNumber];
weakAnimationBlock = animationBlock;
__block int nextLine = lineNumber + 1;
if (nextLine < displayedStringArray.count) {
weakAnimationBlock(nextLine);
}
});
};
animationBlock(0);
}
Simply call
[YOUR_CLASS animateLabel:label withString:#"I\nLove\nStackOverFlow" duration:YOUR_DURATION];]