ios - UIPageControl 点不可见但框架可见

Question

我已经创建了我的第一个 UIPageControl，但我看不到它。

我看到的关于同一问题的每个问题都在谈论点的颜色和背景的颜色是否相同，这就是问题所在 - 这不是我的问题。

事情是这样的:1) 我将 UIPageControl 添加到我的 View 中，其中还包含一个 ScrollView 。 ScrollView 通过几个不同的 View 分页。使用自动布局将 UIPageControl 添加到 ScrollView 的正下方。2)我在 View 加载后更新页面控件的当前页面，然后每次滚动 ScrollView 时。3) 我的 View 背景是深灰色，UIPageControl 的点应该是白色作为默认颜色，但我没有看到它们。但是，当我将 UIPageControl 的背景设置为透明以外的其他颜色时，我可以看到控件的框架就在那里，但我只是看不到这些点。4) 我检查以确保 UIPageControl currentPage 属性设置正确并且是正确的。

我一定是犯了一个愚蠢的错误，但我似乎找不到它。这是我的代码:

//创建UIPageControl

    - (void)viewDidLoad
    {
      [super viewDidLoad];

      self.view.backgroundColor = [UIColor colorWithRed:32/255.0f green:68/255.0f blue:90/255.0f alpha:1];

      //...create self.scrollView and add it to the view

      [self createArrayOfViews]; //this is what makes up the pages in the scroll view
      NSInteger pageCount = self.onboardImages.count; //this array is set in create array of views method above

      self.pageControl.currentPage = 0;
      self.pageControl.numberOfPages = pageCount;

      self.pageViews = [[NSMutableArray alloc] init];
      for (NSInteger i = 0; i < pageCount; ++i) {
        [self.pageViews addObject:[NSNull null]];
      }

      self.scrollView = onBoardScrollView;
      [self.view addSubview:self.scrollView];
      [self.view addConstraints:@[onBoardScrollViewWidth, onBoardScrollViewHeight, onBoardScrollViewCenterY, onBoardScrollViewCenterX]];

      UIPageControl *onBoardImagePageControl = [[UIPageControl alloc]init];
      onBoardImagePageControl.translatesAutoresizingMaskIntoConstraints = NO;
      onBoardImagePageControl.backgroundColor = [UIColor clearColor];

      NSLayoutConstraint *onBoardPageControlTop = [NSLayoutConstraint constraintWithItem:onBoardImagePageControl attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:onBoardScrollView attribute:NSLayoutAttributeBottom multiplier:1.0f constant:10.0f];
      NSLayoutConstraint *onBoardPageControlCenterX = [NSLayoutConstraint constraintWithItem:onBoardImagePageControl attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0f constant:0.0f];

      CGSize sizeForPageControl = [onBoardImagePageControl sizeForNumberOfPages:self.onboardImages.count];

      NSLayoutConstraint *onBoardPageControlWidth = [NSLayoutConstraint constraintWithItem:onBoardImagePageControl attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:sizeForPageControl.width];
      NSLayoutConstraint *onBoardPageControlHeight = [NSLayoutConstraint constraintWithItem:onBoardImagePageControl attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:sizeForPageControl.height];

      self.pageControl = onBoardImagePageControl;

      [self.view addSubview:self.pageControl];
      [self.view addConstraints:@[onBoardPageControlTop, onBoardPageControlCenterX, onBoardPageControlHeight, onBoardPageControlWidth]];

      //... add a few other UI elements

    }

//使用自动布局创建框架后，加载可见页面

    - (void)viewDidLayoutSubviews
    {
      [super viewDidLayoutSubviews];
      CGSize pagesScrollViewSize = self.scrollView.frame.size;
      self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * self.onboardImages.count, 250); 
      self.scrollView.delegate = self;
      [self loadVisiblePages];
    }

//加载可见页面的代码

    - (void)loadVisiblePages {
      // First, determine which page is currently visible
      CGFloat pageWidth = self.scrollView.frame.size.width;
      NSInteger page = (NSInteger)floor((self.scrollView.contentOffset.x * 2.0f + pageWidth) / (pageWidth * 2.0f));

      // Update the page control
      self.pageControl.currentPage = page;

      // Work out which pages you want to load
      NSInteger firstPage = page - 1;
      NSInteger lastPage = page + 1;

      // Purge anything before the first page
      for (NSInteger i=0; i<firstPage; i++) {
        [self purgePage:i];
      }

        // Load pages in our range
      for (NSInteger i=firstPage; i<=lastPage; i++) {
        [self loadPage:i];
      }

        // Purge anything after the last page
      for (NSInteger i=lastPage+1; i<self.onboardImages.count; i++) {
        [self purgePage:i];
      }
    }

    - (void)loadPage:(NSInteger)page {
      if (page < 0 || page >= self.onboardImages.count) {
        // If it's outside the range of what you have to display, then do nothing
        return;
      }

      UIView *pageView = [self.pageViews objectAtIndex:page];
      if ((NSNull*)pageView == [NSNull null]) {

        CGRect frame = self.scrollView.frame;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = -20.0f; //adjust

        //UIImageView *newPageView = [[UIImageView alloc] initWithImage:[self.onboardImages objectAtIndex:page]];
        UIView *newPageView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, self.scrollView.frame.size.width, self.scrollView.frame.size.height)];
        UIView *currentView = [self.onboardImages objectAtIndex:page];
        [newPageView addSubview:currentView];
        currentView.center = newPageView.center;
        newPageView.contentMode = UIViewContentModeScaleAspectFit;
        newPageView.frame = frame;
        [self.scrollView addSubview:newPageView];
        [self.pageViews replaceObjectAtIndex:page withObject:newPageView];
      }
    }

// ScrollView 委托(delegate)方法继续加载可见页面

    - (void)scrollViewDidScroll:(UIScrollView *)scrollView {
      // Load the pages that are now on screen
      [self loadVisiblePages];
    }

//从 ScrollView 中删除看不见的页面

    - (void)purgePage:(NSInteger)page {
      if (page < 0 || page >= self.onboardImages.count) {
        // If it's outside the range of what you have to display, then do nothing
        return;
      }

      // Remove a page from the scroll view and reset the container array
      UIView *pageView = [self.pageViews objectAtIndex:page];
      if ((NSNull*)pageView != [NSNull null]) {
        [pageView removeFromSuperview];
        [self.pageViews replaceObjectAtIndex:page withObject:[NSNull null]];
      }
    }

感谢任何帮助。

Answer 1

顺序好像不对。您正在为被覆盖的对象设置 currentPage 和 pageCount。

  //Set here
  self.pageControl.currentPage = 0;
  self.pageControl.numberOfPages = pageCount;

  UIPageControl *onBoardImagePageControl = [[UIPageControl alloc]init];
  onBoardImagePageControl.translatesAutoresizingMaskIntoConstraints = NO;
  onBoardImagePageControl.backgroundColor = [UIColor clearColor];

  //Overwritten here
  self.pageControl = onBoardImagePageControl;

  [self.view addSubview:self.pageControl];