Making uitextview scroll programmatically

问题:

I want to make my uitextview to scroll automatically whenever the application is launched. Can anyone help me with a detailed code? I am new to iPhone SDK.

回答1:

.h file

@interface Credits : UIViewController 
{
    NSTimer *scrollingTimer;

    IBOutlet UITextView *textView;


}
@property (nonatomic , retain) IBOutlet UITextView *textView;

- (IBAction) buttonClicked ;

- (void) autoscrollTimerFired;

@end

.m file

- (void) viewDidLoad
{       
    // it prints the initial position of text view 
    NSLog(@"%f %f",textView.contentSize.width , textView.contentSize.height);

    if (scrollingTimer == nil)
    {
        // A timer that updates the content off set after some time so it can scroll 
        // you can change time interval according to your need (0.06)
        // autoscrollTimerFired is the method that will be called after specified time interval. This method will change the content off set of text view
        scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:(0.06)
                         target:self selector:@selector(autoscrollTimerFired) userInfo:nil repeats:YES];        
    }
}

- (void) autoscrollTimerFired
{
    CGPoint scrollPoint = self.textView.contentOffset; // initial and after update
    NSLog(@"%.2f %.2f",scrollPoint.x,scrollPoint.y);
    if (scrollPoint.y == 583) // to stop at specific position 
    {
        [scrollingTimer invalidate];
        scrollingTimer = nil;
    }
    scrollPoint = CGPointMake(scrollPoint.x, scrollPoint.y + 1); // makes scroll
    [self.textView setContentOffset:scrollPoint animated:NO];
    NSLog(@"%f %f",textView.contentSize.width , textView.contentSize.height);

}

Hope it helps you....

回答2:

UITextView derives from UIScrollview so you can set the scrolling position using -setContentOffset:animated:.

Assuming you want to scroll smoothly at the speed of 10 points per second, you'd do something like that.

- (void) scrollStepAnimated:(NSTimer *)timer {
    CGFloat scrollingSpeed = 10.0; // 10 points per second
    NSTimeInterval repeatInterval = [timer timeInterval]; // ideally, something like 1/30 or 1/10 for a smooth animation

    CGPoint newContentOffset = CGPointMake(self.textView.contentOffset.x, self.textView.contentOffset.y + scrollingSpeed * repeatInterval);
    [self.textView setContentOffset:newContentOffset animated:YES];
}

Of course you have to setup the timer and be sure to cancel the scrolling when the view disappears and so on.