需要示例代码来实现基于分页的UIScrollView [英] Need sample code to implement Paging Based UIScrollView

问题描述

我是iOS开发的新手.谁能给我一个基于分页的scrollview的工作示例项目/教程?当用户向下滚动时，我需要从Web服务在表视图中加载更多数据.我已经花了很多时间，但是找不到适合我需要的东西.任何帮助将不胜感激.

I am new to iOS development. Can anyone give me a working sample project/ tutorial of paging based scrollview? I need to load more data in my table view from a webservice as user scrolls down. I have spent a lot of time, but could not find anything that suits my need. Any help will be greatly appreciated.

我能够找出问题的解决方案.现在，我尝试根据y偏移量来检测上下滚动.问题是它始终将阻力读为向下，即使它是向上的.这就是我试图检测滚动方向的方式:

I was able to figure out the solution of my problem. Now I am trying to detect scroll up and down based on the y offset difference. The problem is it always reads the drag to be downwards even if it is upward. This is how I am trying to detect the scroll direction:

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    CGPoint scrollOffSet =  scrollView.contentOffset;
    NSLog(@"Current Content offset: , y = %f", scrollOffSet.y);
    NSLog(@"Previous offset , y = %f", self.previousYOffset);

    if(scrollOffSet.y > self.previousYOffset)
    {
        self.previousYOffset = scrollOffSet.y;
        NSLog(@"Scrolled Down");
        self.nextPageNumber++;
        //Here I send the request to fetch data for next page number
    }
    else {
        NSLog(@"Scrolled up");
        self.previousYOffset = scrollOffSet.y;
    }

}


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

    CGPoint scrollOffSet =  scrollView.contentOffset;
    NSLog(@"Current Content offset: y = %f", scrollOffSet.y);
}

问题是:无论我向上还是向下滚动，它始终显示向下滚动"，因此即使不打算请求，它也会继续获取下一页的数据.另外，它在上/下滚动中返回的y偏移位置也非常令人困惑.请指导我如何准确检测向上滚动?

The problem is: either i scroll up or down, it will always display "scrolled down", thus it goes to fetch data for next page number even if it was not intended to request. Plus, the y offset positions it returns on up/down scroll are also very confusing. Please guide me how to accurately detect an upside scroll?

推荐答案

您是指可交换"的 UIScrollView 吗?

分页 UIScrollView 非常简单.首先，请确保将 pagingEnabled 属性设置为 YES . UIScrollView 将使用它自己的框架作为页面的大小(如视口).

Paging a UIScrollView is quite easy. First make sure you have the pagingEnabled property set to YES. The UIScrollView will use it's own frame as the size of a page (like a viewport).

使用 contentSize 属性确定可滚动区域.

示例:

//scrollView is a UIScrollView instance  
int pageCount = 3;  
scrollView.pagingEnabled = YES;  
scrollView.contentSize = CGSizeMake(scrollView.frame.width*pageCount, scrollView.frame.height);

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