How to create auto scrolling UITextView in the Xcode - ios

Question

I try to create a UITexView with auto scrolling when press button start. And have a button stop, when pressed it will stop scrolling. Pressing button start again and it will continues to scroll down. How to handle this function.
I have research some code that this code below work with me.
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSLog(#"%f %f",_txvSentence.contentSize.width , _txvSentence.contentSize.height);
if (scrollingTimer == nil) {
scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:(35.0/1000.0)
target:self
selector:#selector(autoscrollTimerFired:)
userInfo:nil
repeats:YES];
NSLog(#"%#",scrollingTimer);
}
}
- (void)autoscrollTimerFired:(NSTimer*)timer {
CGPoint scrollPoint = self.txvSentence.contentOffset;
//scrollPoint = CGPointMake(scrollPoint.x, scrollPoint.y + 1);
scrollPoint = _txvSentence.contentOffset;
scrollPoint.y= scrollPoint.y+1;
[_txvSentence setContentOffset:scrollPoint animated:NO];
//[self.txvSentence setContentOffset:scrollPoint animated:NO];
}
But i cannot stop this animation. And how to set dynamic duration such as when come to the end of text it automatically stop.
Sorry because my bad english. If not understand please tell me where I will explain it clearly.

Answer 1

Try this:
self.scrollView.scrollEnabled = NO;
CGFloat scrollHeight = 100;
//===
- (void) spinWithOptions: (UIViewAnimationOptions) options {
// this spin completes 360 degrees every 2 seconds
[UIView animateWithDuration:10
delay:0
options:options
animations:^{
self.scrollView.contentOffset = CGPointMake(0, scrollHeight);
}
completion:^(BOOL finished) {
if (finished) {
if (animating) {
// if flag still set, keep spinning with constant speed
[self spinWithOptions: UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction];
} else if (options != UIViewAnimationOptionCurveEaseOut) {
// one last spin, with deceleration
[self spinWithOptions: UIViewAnimationOptionCurveEaseOut];
}
}
}];
}
- (void) startAnimating {
if (!animating) {
animating = YES;
[self spinWithOptions: UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction];
}
}
- (void) stopAnimating {
// set the flag to stop spinning after one last 90 degree increment
animating = NO;
}

Answer 2

You can use NSTimer.
// Global var
CGFloat scrollHeight = MAX_HEIGHT;
CGFloat currentOffsetY = 0.0f;
NSTimer *timer;
self.timer = [NSTimer scheduledTimerWithTimeInterval:YOUR_TIME_INTERVAL target:self selector:#selector(scrollText:) userInfo:nil repeats:YES];
- (void)scrollText:(NSTimer *)timer {
currentOffsetY++;
if (currentOffsetY >= MAX_HEIGHT) {
[self.timer invalide];
}
self.scrollView.contentOffset = CGPointMake(0, currentOffsetY);
}
// Your button action
- (void)stopAnimation:(UIButton *)button {
[self.timer invalide];
}