Detect UITextView scroll location

问题

I am trying to implement a form of a Terms & Conditions page where the "Proceed" button is only enabled once the user has scrolled to the bottom of a UITextView. So far I have set my class as a UIScrollView delegate & have implemented the method below:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    NSLog(@"Checking if at bottom of UITextView");
    CGPoint bottomOffset = CGPointMake(0,self.warningTextView.frame.size.height);
    //if ([[self.warningTextView contentOffset] isEqualTO:bottomOffset])
    {
    }    
}

I have commented the if statement because I am not sure how to check if the UITextView is at the bottom.

回答1:

UITextView is a UIScrollView subclass. Therefore the UIScrollView delegate method you are using is also available when using UITextView.

Instead of using scrollViewDidEndDecelerating, you should use scrollViewDidScroll, as the scrollview may stop scrolling without deceleration.

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (scrollView.contentOffset.y >= scrollView.contentSize.height - scrollView.frame.size.height)
    {
        NSLog(@"at bottom");
    }
}

回答2:

A Swift version for this question:

func scrollViewDidScroll(_ scrollView: UIScrollView) {

    if scrollView.contentOffset.y >= scrollView.contentSize.height - scrollView.frame.size.height {

        print( "View scrolled to the bottom" )

    }
}

回答3:

This should solve it. It works. I am using it.

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView 
{
    float bottomEdge = scrollView.contentOffset.y + scrollView.frame.size.height;
    if (bottomEdge >= scrollView.contentSize.height) 
    {
        // we are at the end
    }
}

来源：https://stackoverflow.com/questions/13969970/detect-uitextview-scroll-location