Zoran Simic Zoran Simic - 3 months ago 14
iOS Question

How to make a blinking (or flashing) cursor on iphone?

I'm trying to create a custom "blinking cursor" in UIKit, I've tried as shown below, having 2 functions that basically keep calling each other until the cursor is hidden. But this leads to a nice infinite recursion... for some reason the functions call each other right away, not each half-second as expected.

I tried returning if the 'finished' parameter is not YES (by uncommenting the 'if (!ok)' line), but that leads to no animation at all...

Any better idea? Did I miss something, is there a much-easier way to make a "blinking cursor"?

- (void)onBlinkIn:(NSString *)animationID finished:(BOOL)ok context:(void *)ctx {
if (cursorView.hidden) return;
//if (!ok) return;
[UIView beginAnimations:nil context:UIGraphicsGetCurrentContext()];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:0.5f];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(onBlinkOut:finished:context:)];
cursorView.textColor = [UIColor grayColor];
[UIView commitAnimations];
}

- (void)onBlinkOut:(NSString *)animationID finished:(BOOL)ok context:(void *)ctx {
if (cursorView.hidden) return;
[UIView beginAnimations:nil context:UIGraphicsGetCurrentContext()];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:0.5f];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(onBlinkIn:finished:context:)];
cursorView.textColor = [UIColor clearColor];
[UIView commitAnimations];
}

Answer

On the delegate:

- (void)blinkAnimation:(NSString *)animationId finished:(BOOL)finished target:(UIView *)target
{
    if (shouldContinueBlinking) {
        [UIView beginAnimations:animationId context:target];
        [UIView setAnimationDuration:0.5f];
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(blinkAnimation:finished:target:)];
        if ([target alpha] == 1.0f)
            [target setAlpha:0.0f];
        else
            [target setAlpha:1.0f];
        [UIView commitAnimations];
    }
}

And to start the animation:

shouldContinueBlinking = YES;
[self blinkAnimation:@"blinkAnimation" finished:YES target:cursorView];

Also, ensure your class has a shouldContinueBlinking instance variable