UIPageControl UIControlEventValueChanged - how do I know previous value?

Question

I've got a UIPageControl object working great in my app, except that I am not handling the default 'tap to advance/decrement' behavior.

I need to:

• handle it in my app
• know what the current and previous values of the UIPageControl is.

I know I can capture the 'new' value on UIControlEventValueChanged, but how would I know the 'old'? I manually setCurrentPage in several places in my code, but saving the old state somewhere there could lead to bugs and is sort of a hack I think.

Answer 1

I don't think there is a property to keep the previous page, but why not define one? You can keep all the previous page numbers in an NSMutableArray object and;

• When you are about to go to a new page, add the current one to the array before you go,

• Whenever you want to come back a previous page, get the lastObject of you array and remove it.

  - (NSInteger)previousPageNumber
  {
      NSInteger pageNumber = 0;
      if(self.previousPagesArray.count > 0)
      {
          pageNumber = [[self.previousPagesArray lastObject] intValue];
          [self.previousPagesArray removeLastObject];
      }
  
      return pageNumber;
  }
  

and

-(void)goToNextPage
{
    NSNumber *pageNumber = [NSNumber numberWithInt:self.pageControl.currentPage];
    [self.previousPagesArray addObject:pageNumber];
    //go to next page
}