我正在尝试实现方法scrollViewWillBeginDragging。 调用此方法时,我检查用户是否选择了滚动视图中的按钮之一处于状态:已选择。如果没有,那么我会显示一个 UIAlert 来通知用户。
我的问题是,如果用户从右向左滚动(从右侧拉下一个视图),我只想调用按钮选择(NextQuestion )方法。但是,如果他们从左到右滚动,那么我希望它正常滚动。
目前,无论用户向哪个方向滚动都会调用 checker 方法。我怎样才能只在他们从Right To Left滚动时调用一个方法?
这是我目前实现它的方式:
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
[self NextQuestion:scrollView];
}
-(IBAction)NextQuestion:(id)sender
{
CGFloat pageWidth = scrollView.frame.size.width;
int page = floor((scrollView.contentOffset.x - pageWidth) / pageWidth) + 1;
NSInteger npage = 0;
CGRect frame = scrollView.frame;
// Check to see if the question has been answered. Call method from another class.
if([QuestionControl CheckQuestionWasAnswered:page])
{
pageNumber++;
NSLog(@"Proceed");
if(([loadedQuestionnaire count] - 1) != page)
{
[self loadScrollViewWithPage:page - 1];
[self loadScrollViewWithPage:page];
[self loadScrollViewWithPage:page + 1];
}
// update the scroll view to the appropriate page
frame = scrollView.frame;
frame.origin.x = (frame.size.width * page) + frame.size.width;
frame.origin.y = 0;
[self.scrollView scrollRectToVisible:frame animated:YES];
}
// If question has not been answered show a UIAlert with instructions.
else
{
UIAlertView *alertNotAnswered = [[UIAlertView alloc] initWithTitle:@"Question Not Answered"
message:@"You must answer this question to continue the questionnaire."
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
[alertNotAnswered show];
}
}
解决方案 1 的代码:
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
NSLog(@"%f",scrollView.contentOffset.x);
if (scrollView.contentOffset.x < lastOffset) // has scrolled left..
{
lastOffset = scrollView.contentOffset.x;
[self NextQuestion:scrollView];
}
}