How should i code this paging?

问题

I've been struggling with some code for a paging for a couple of days (YES! days) now but can't get it to work properly, probably because I don't have any experience on this kind of problems yet.

the paging I'm trying to do should look something like this:

1 2 3 4 5 6 ... 101

When i click on number 5 i would like it to display the numbers like this:

1 ... 3 4 5 6 7 ... 101

when I'm at the last couple of pages i want it to look similar to the first one:

1 ... 96 97 98 99 100 101

The bold number is the page that you're currently viewing.

I want the dots to appear only when there is more than 7 pages available, if not it should look like a normal paging would look like:

1 2 3 4 5 6 7

Right now i want to display 10 items per page.

The language i want to use is C# (ASP.NET) and would like to, later on make this a usercontrol (Where i should set the properties TotalNumberOfItems, ItemsPerPage and so on).

The question: How do i write the code to loop out the numbers on the correct places? :)

回答1:

How about (Make it Bold is somewhat psuedoCode cause I don't know what UI you're in...)

   private static string BuildPaging(int pageNo, int pageCount)
   {
      StringBuilder sb = new StringBuilder();

      for(int i = 1; i < pageCount; i++)
      {
         if (i == pageNo) 
             sb.Append([Make it Bold] + i.ToString("0") + [Make it not Bold]);
         else if (1 > pageNo - 3 && i < pageNo + 3)
             sb.Append(i.ToString("0"));
         else if ((i == 2 && pageNo > 4) ||        
                  (i == PageCount - 1 && pageNo < PageCount - 2))
             sb.Append("...");
      }
      return sb.ToString();
   }

Only thing is how to make it bold (Depends on whether you're in WinForms or ASP.Net... ... And add stuff to make it a clickable link...

回答2:

You need maximum pager inner list size (those between dots), page size, documents counter and current page index. Then you can use algorithm like this:

_pagesTotal = DocumentsTotal / DocumentsPerPage;
if ( DocumentsTotal % DocumentsPerPage > 0 )
{
    _pagesTotal++;
}
// we want current page in the middle
// PageBlockMaxSize is the size of those dotted out pages
int halfBlock = PageBlockMaxSize / 2;
if ( CurrentPageIndex > PageBlockMaxSize )
{
    // add some code here to show first page link and following dots
    // ...    
    _firstPageInBlockIndex = CurrentPageIndex - halfBlock;
}
else
{
    // we don't need any dots here
_firstPageInBlockIndex = 1;
}

if ( _pagesTotal - CurrentPageIndex > PageBlockMaxSize )
{
    // here show last page link and preceeding dots. you can use _pagesTotal as it's text
    // ...    
    _lastPageInBlockIndex = CurrentPageIndex + halfBlock;
}
else
{
    // we don't need any dots here
    _lastPageInBlockIndex = _pagesTotal;
}

// hide next-previous buttons if they are not needed
if ( CurrentPageIndex == 1 )
{
    spanPrev.Visible = false;
}
else if ( CurrentPageIndex == _pagesTotal )
{
    spanNext.Visible = false;
}

// and when we are ready we build list of page counters
var pages = new List<int>();
for ( int page = _firstPageInBlockIndex;
      page <= _lastPageInBlockIndex;
      page++ )
{
    pages.Add( page );
}

and then we can databind this list to some repeater or use it some other way to display common links between those dots (or without them).

回答3:

I've done something like that. It has a few that are different from what you want exactly, but should be helpful. This was a quick and dirty solution to a problem and has a number of efficiency issues, but it's a good start.

public class PagingHelper
{
    public IEnumerable<int> GetListOfPages(int currentPage, int pagesAroundCurrent, int totalPages)
    {
        var pages = new Dictionary<int, int>();
        double powerOfTenTotalPages = Math.Floor(Math.Log10(totalPages));
        if ((int)powerOfTenTotalPages == 0)
        {
            powerOfTenTotalPages = 1;
        }
        pages.Add(1, 1);
        if (!pages.ContainsKey(totalPages))
        {
            pages.Add(totalPages, totalPages);
        }

        for (int loop = 1; loop <= powerOfTenTotalPages + 1; loop++)
        {
            GetPages(pages, currentPage, pagesAroundCurrent, totalPages, (int)Math.Pow(10, loop - 1));
        }
        return pages.OrderBy(k=>k.Key).Select(p=>p.Key).AsEnumerable();
    }

    private void GetPages(Dictionary<int, int> pages, int currentPage, int pagesAroundCurrent, int totalPages, int jump)
    {
        int startPage = ((currentPage / jump) * jump) - (pagesAroundCurrent * jump);

        if (startPage < 0)
        {
            startPage = 0;
            pagesAroundCurrent = 10;
        }

        int endPage = currentPage + (pagesAroundCurrent * jump);
        if (endPage > totalPages)
        {
            endPage = totalPages;
        }
        AddPagesToDict(pages, startPage, endPage, jump);
    }

    private void AddPagesToDict(Dictionary<int, int> pages, int start, int end, int jump)
    {
        for (int loop = start; loop <= end; loop += jump)
        {
            if (!pages.ContainsKey(loop))
            {
                if (loop > 0)
                {
                    pages.Add(loop, loop);
                }
            }
        }
    }
}

Sample output -

Current Page:1 Total Pages:40 Pages to display around current page:5

1 2 3 4 5 6 7 8 9 10 11 20 30 40

Current Page:90 Total Pages:600 Pages to display around current page:5

1 40 50 60 70 80 85 86 87 88 89 90 91 92 93 94 95 100 110 120 130 140 200 300 400 500 600

Current Page:147 Total Pages:6825 Pages to display around current page:5

For full details see a post here.

来源：https://stackoverflow.com/questions/1928809/how-should-i-code-this-paging

标签

paging