以编程方式将UIPageControl与UIScrollView链接

Question

以编程方式将UIPageControl与UIScrollView链接

57

我正在创建一个简单的幻灯片视图，想要将UIPageControl与UIScrollView链接起来。这应该不难，但是我在任何地方都没有找到简单的解决方案。以下是我的代码。

HelpViewController.h

#import <UIKit/UIKit.h>

@interface HelpViewController : UIViewController{
}
@end

HelpViewController.m

#import "HelpViewController.h"

@interface HelpViewController ()

@end

@implementation HelpViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    CGRect scrollViewFrame = CGRectMake(0, 62, 320, 404);
    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:scrollViewFrame];
    [self.view addSubview:scrollView];
    CGSize scrollViewContentSize = CGSizeMake(640, 404);
    [scrollView setContentSize:scrollViewContentSize];
    UILabel *label  = [[UILabel alloc] initWithFrame:CGRectMake(200, 200, 50, 21)];
    [label setText:@"Hello"];
    [scrollView addSubview:label];
    [scrollView setPagingEnabled:YES];
    scrollView.showsHorizontalScrollIndicator = NO;
    UIPageControl *pageControl = [[UIPageControl alloc] init]; 
    pageControl.frame = CGRectMake(110,5,100,100); 
    pageControl.numberOfPages = 2; 
    pageControl.currentPage = 0; 
    [self.view addSubview:pageControl];
    pageControl.backgroundColor = [UIColor redColor];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

- Dan Carew

我在这里正确回答了这个问题 https://dev59.com/r0_Ta4cB1Zd3GeqPE-yx#14230698 更好的做法是在一个地方回答... 我在那里修复了提出的更改。 - Renetik

5个回答

54

设置起来其实很简单。首先需要创建滚动视图和页面控制器。确保你在类的接口中实现了UIScrollViewDelegate。

    UIScrollView * scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * 3, scrollView.frame.size.height);
    scrollView.delegate = self;

    UIPageControl * pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, 90, scrollView.frame.size.width, 20)];
    pageControl.numberOfPages = scrollView.contentSize.width/scrollView.frame.size.width;
    [pageControl addTarget:self action:@selector(changePage:) forControlEvents:UIControlEventValueChanged];

那么你需要添加以下两个方法：

- (IBAction)changePage:(id)sender {
    CGFloat x = pageControl.currentPage * scrollView.frame.size.width;
    [scrollView setContentOffset:CGPointMake(x, 0) animated:YES];
}

-(void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView  {
    NSInteger pageNumber = roundf(scrollView.contentOffset.x / (scrollView.frame.size.width));
    pageControl.currentPage = pageNumber;
}

这些方法增加了页面控件和滚动视图之间所需的通信。

- James Andrews

要正确确定pageNumber，您需要乘以pageControl.numberOfPages。 - Gerry Shaw

4

以下代码适用于Swift:

func addScrollView() {        
    let scrollView = UIScrollView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
    let numberOfPages: CGFloat = 4
    scrollView.contentSize = CGSize(width: scrollView.frame.width * numberOfPages, height: scrollView.frame.height * numberOfPages)
    scrollView.delegate = self
    scrollView.isPagingEnabled = true

    let pageControl = UIPageControl(frame: CGRect(x: 0, y: scrollView.frame.height - 37, width: scrollView.frame.width, height: 37))
    pageControl.numberOfPages = Int(numberOfPages)
    pageControl.currentPage = 0
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let value = scrollView.contentOffset.x / scrollView.frame.size.width
    pageControl.currentPage = Int(round(value))
}

- Bilal

2

要获取精确的页面索引而不舍入值，只需在滚动视图的scrollViewDidEndDecelerating代理方法中放置pagecontrol.currentpage。这对我有效！

- Harshit K

0

所有这些答案都很好，但我想提供一种替代方案，使用ReactiveCocoa！

以下代码假设您有一个名为scrollView和一个名为pageControl的属性。

[RACObserve(self.scrollView, contentOffset)
  subscribeNext:^(NSValue* value){
      CGPoint offset = [value CGPointValue];
      CGFloat fractional = offset.x/self.scrollView.width;
      [self.pageControl setCurrentPage:lroundf(fractional)];
  }];

这里发生的一切都是在观察scrollView的contentOffset属性的变化，并在每个next事件（即每次属性值更改时）计算页面索引。

唯一的缺点是您必须取消勾选CGPoint，但好处是根本不需要UIScrollViewDelegate代码！

- barndog

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Jonas Schnelli · Accepted Answer

或许这个方法适合你

别忘了把UIScrollView的delegate设置为self（或者你在下面的selector所在的位置）。

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGFloat pageWidth = self.scrollView.frame.size.width; // you need to have a **iVar** with getter for scrollView
    float fractionalPage = self.scrollView.contentOffset.x / pageWidth;
    NSInteger page = lround(fractionalPage);
    self.pageControl.currentPage = page; // you need to have a **iVar** with getter for pageControl
}

对于您的代码，它将如下所示：

.h文件

#import <UIKit/UIKit.h>

@interface HelpViewController : UIViewController{
}

@property (nonatomic, retain) UIScrollView *scrollView;
@property (nonatomic, retain) UIPageControl * pageControl;
@end

.m 文件

#import "HelpViewController.h"

@interface HelpViewController ()

@end

@implementation HelpViewController
@synthesize scrollView=scrollView_;
@synthesize pageControl=pageControl_;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    CGRect scrollViewFrame = CGRectMake(0, 62, 320, 404);
    self.scrollView = [[[UIScrollView alloc] initWithFrame:scrollViewFrame] autorelease];
    self.scrollView.delegate = self;
    [self.view addSubview:self.scrollView];
    CGSize scrollViewContentSize = CGSizeMake(640, 404);
    [self.scrollView setContentSize:scrollViewContentSize];
    UILabel *label  = [[UILabel alloc] initWithFrame:CGRectMake(200, 200, 50, 21)];
    [label setText:@"Hello"];
    [self.scrollView addSubview:label];
    [self.scrollView setPagingEnabled:YES];
    self.scrollView.showsHorizontalScrollIndicator = NO;
    self.pageControl = [[[UIPageControl alloc] init] autorelease]; 
    self.pageControl.frame = CGRectMake(110,5,100,100); 
    self.pageControl.numberOfPages = 2; 
    self.pageControl.currentPage = 0; 
    [self.view addSubview:self.pageControl];
    pageControl.backgroundColor = [UIColor redColor];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

 - (void)scrollViewDidScroll:(UIScrollView *)scrollView {
        CGFloat pageWidth = self.scrollView.frame.size.width;
        float fractionalPage = self.scrollView.contentOffset.x / pageWidth;
        NSInteger page = lround(fractionalPage);
        self.pageControl.currentPage = page; 
    }


@end