在ScrollView中找到用户将手指拖到的位置的X位置

Question

I have a scrollview and I'm watching user input. I would like to know where their finger currently is on the X plane. Is this possible through the ScrollView and/or its delegate or do I have to override touchesBegan , etc?

Answer 1

I'm assuming you set up your scroll view delegate. If you did, then you only need to implement the scrollViewDidScroll: method from the UIScrollViewDelegate protocol...

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGPoint touchPoint = [scrollView.panGestureRecognizer locationInView:scrollView];
    NSLog(@"Touch point: (%f, %f)", touchPoint.x, touchPoint.y);
}

This will update while the user is scrolling.

Additional info: Note that if you have something like a UIPageControl , that your scroll view is navigating between, you may have to calculate the x position based on the number of pages (ie if each page is 100 pixels wide, page 0 will start at point 0, page one at point 100, etc..).

Answer 2

CGPoint touchPoint = [scrollView.panGestureRecognizer locationInView:scrollView];
CGFloat x = touchPoint.x;

Answer 3

CGPoint point = [_scrollView locationOfTouch:touchIndex inView:_scrollView];

touchindex: 0 for first touch and 1, 2,3 so on

if inview:nil then point will be in the window base coordinate sysytem

CGFloat x = point.x;
CGFloat y  = point.y

Answer 4

I use the panGesture of the scrollView because it's more accurate if you want to know the position of the x plane when you have only vertical scroll.

[self.scrollView.panGestureRecognizer addTarget:self action:@selector(handlePanForScrollView:)];

and then:

- (void)handlePanForScrollView:(UIPanGestureRecognizer *)gesture {
    CGPoint positionInView = [gesture locationInView:self.scrollView];

}