如何将视图添加到 UIScrollView 并使其与 UIPageControl 保持同步？

Question

我需要在我的应用程序中动态创建一些视图，并再次动态地在它们上面放置一些按钮。如果按钮的数量（计数）超过 10 个，我想将按钮放置在新视图上，并且视图之间的转换必须使用 UIPageControl。尽管我在苹果的开发者页面上进行了谷歌搜索和搜索，但我找不到解决问题的方法。有人可以帮忙吗？

Answer 1

使用 addSubview 方法将视图添加为 UIScrollView 的并排子视图。然后将 UIPageControl 与 UIScrollView 结合使用，如这个 示例。

---

我创建了一个类来管理 UIScrollView、UIPageControl 和 UIView 数组。这是我在自己的代码中使用的简化版本。它执行以下操作：

• 设置滚动视图以显示 UIView 数组。它不关心视图是否是动态生成的。
• 处理滚动和页面控制事件。
• 将滚动视图与页面控件同步。

---

PageViewManager.h

#import <Foundation/Foundation.h>

@interface PageViewManager : NSObject <UIScrollViewDelegate>
{
    UIScrollView* scrollView_;
    UIPageControl* pageControl_;
    NSArray* pages_;
    BOOL pageControlUsed_;
    NSInteger pageIndex_;
}

- (id)initWithScrollView:(UIScrollView*)scrollView
             pageControl:(UIPageControl*)pageControl;
- (void)loadPages:(NSArray*)pages;
- (void)loadControllerViews:(NSArray*)pageControllers;

@end

---

PageViewManager.m

#import "PageViewManager.h"

@interface PageViewManager ()

- (void)pageControlChanged;

@end

@implementation PageViewManager

- (id)initWithScrollView:(UIScrollView*)scrollView
             pageControl:(UIPageControl*)pageControl
{
    self = [super init];
    if (self)
    {
        scrollView_ = scrollView;
        pageControl_ = pageControl;
        pageControlUsed_ = NO;
        pageIndex_ = 0;

        [pageControl_ addTarget:self action:@selector(pageControlChanged)
               forControlEvents:UIControlEventValueChanged];
    }
    return self;
}

/*  Setup the PageViewManager with an array of UIViews. */
- (void)loadPages:(NSArray*)pages
{
    pages_ = pages;
    scrollView_.delegate = self;
    pageControl_.numberOfPages = [pages count];

    CGFloat pageWidth  = scrollView_.frame.size.width;
    CGFloat pageHeight = scrollView_.frame.size.height;

    scrollView_.pagingEnabled = YES;
    scrollView_.contentSize = CGSizeMake(pageWidth*[pages_ count], pageHeight);
    scrollView_.scrollsToTop = NO;
    scrollView_.delaysContentTouches = NO;

    [pages_ enumerateObjectsUsingBlock:^(id obj, NSUInteger index, BOOL *stop)
    {
        UIView* page = obj;
        page.frame = CGRectMake(pageWidth * index, 0,
                                pageWidth, pageHeight);
        [scrollView_ addSubview:page];
    }];
}

/*  Setup the PageViewManager with an array of UIViewControllers. */
- (void)loadControllerViews:(NSArray*)pageControllers
{
    NSMutableArray* pages = [NSMutableArray arrayWithCapacity:
                             pageControllers.count];
    [pageControllers enumerateObjectsUsingBlock:
        ^(id obj, NSUInteger idx, BOOL *stop)
        {
            UIViewController* controller = obj;
            [pages addObject:controller.view];
        }];

    [self loadPages:pages];
}

- (void)pageControlChanged
{
    pageIndex_ = pageControl_.currentPage;

    // Set the boolean used when scrolls originate from the page control.
    pageControlUsed_ = YES;

    // Update the scroll view to the appropriate page
    CGFloat pageWidth  = scrollView_.frame.size.width;
    CGFloat pageHeight = scrollView_.frame.size.height;
    CGRect rect = CGRectMake(pageWidth * pageIndex_, 0, pageWidth, pageHeight);
    [scrollView_ scrollRectToVisible:rect animated:YES];
}

- (void)scrollViewDidScroll:(UIScrollView*)sender
{
    // If the scroll was initiated from the page control, do nothing.
    if (!pageControlUsed_)
    {
        /*  Switch the page control when more than 50% of the previous/next
            page is visible. */
        CGFloat pageWidth = scrollView_.frame.size.width;
        CGFloat xOffset = scrollView_.contentOffset.x;
        int index = floor((xOffset - pageWidth/2) / pageWidth) + 1;
        if (index != pageIndex_)
        {
            pageIndex_ = index;
            pageControl_.currentPage = index;
        }
    }
}

- (void)scrollViewWillBeginDragging:(UIScrollView*)scrollView
{
    pageControlUsed_ = NO;
}

- (void)scrollViewDidEndDecelerating:(UIScrollView*)scrollView
{
    pageControlUsed_ = NO;
}

@end

---

要使用此类，请将其嵌入到包含 UIScrollView 和 UIPageControl 的 UIViewController 中。

用法：

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    // Create some views dynamically
    UIView* v1 = ...
    UIView* v2 = ...

    // Put the views inside an NSArray:
    NSArray* pages_ = [NSArray arrayWithObjects:v1, v2, nil];

    /* Create the PageViewManager, which is a member (or property) of this
       UIViewController. The UIScrollView and UIPageControl belong to this 
       UIViewController, but we're letting the PageViewManager manage them for us. */
    pageViewManager_ = [[PageViewManager alloc]
                        initWithScrollView:self.scrollView
                               pageControl:self.pageControl];

    // Make the PageViewManager display our array of UIViews on the UIScrollView.
    [pageViewManager_ loadViews:pages_];
}

我的示例代码假设您正在使用 ARC。