Question

My project needs to add and delete a uiwebview to uiscrollview at runtime. Means, when we scroll it horizontally (left or right) when paging is enabled, then a new view get added to the uiscrollview and it traverse to it.

Is it possible to detect the left or right scrolling in uiscrollview?

Plz tell me the best possible solution, sample code or any tutorial.

Thanks in advance

Answer 1

In such cases, we should have paging enabled in our scroll view.

Lets say you have scroll view of size 320×480, and it is supposed to show 10 pages, where size of each page is 320×480, making content size of scroll view as 320*10 x 480.

The best way to determine the current page is by using the content offset value of the scroll view.
So, in the beginning, when scrollview is showing 1st page, its content offset would be x=0, y=0.

For 2nd page x=320, y=0.
Thus we can get the current page value by dividing the contentOffset.x by page-width.
Thus, 0/320 = 0, means 1st page. 320/320 = 1, means 2nd page, and so on.

Thus, if we have current page value with us, we can determine in which direction the scroll view is moving, as follows:

-(void) scrollViewDidScroll:(UIScrollView *)scrollView{

    int currentPageOffset = currentPage * PAGE_WIDTH;
    if (self.pageScrollView.contentOffset.x >= currentPageOffset + PAGE_WIDTH) {
        // Scroll in right direction. Reached the next page offset.
        // Settings for loading the next page.
        currentPage = self.pageScrollView.contentOffset.x/PAGE_WIDTH;
    }else if (self.pageScrollView.contentOffset.x <= currentPageOffset - PAGE_WIDTH) {
        // Scroll in left direction. Reached the previous page offset.
        // Setting for loading the previous page.
        currentPage = self.pageScrollView.contentOffset.x/PAGE_WIDTH;
    }

}