iOS：日历日视图转换

Question

Apple 如何实现 iPhone 日历日视图在日期之间的转换？当您在日视图上滑动手指时，它看起来有点像旋转木马，当日视图在屏幕的一半处时，顶部的日期会发生变化。

我自己重新创建了日视图，但需要弄清楚如何在日之间进行转换。

Answer 1

如果我必须猜测的话？在 UIScrollView 中使用 3 个窗格，例如 此方法。

- (void)viewDidLoad 
{
  [super viewDidLoad];

  documentTitles = [[NSMutableArray alloc] init];

  // create our array of documents
  for (int i = 0; i < 10; i++) {
    [documentTitles addObject:[NSString stringWithFormat:@"Document %i",i+1]];
  }

  // create placeholders for each of our documents
  pageOneDoc = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
  pageTwoDoc = [[UILabel alloc] initWithFrame:CGRectMake(320, 0, 320, 44)];
  pageThreeDoc = [[UILabel alloc] initWithFrame:CGRectMake(640, 0, 320, 44)];

  pageOneDoc.textAlignment = UITextAlignmentCenter;
  pageTwoDoc.textAlignment = UITextAlignmentCenter;
  pageThreeDoc.textAlignment = UITextAlignmentCenter;

  // load all three pages into our scroll view
  [self loadPageWithId:9 onPage:0];
  [self loadPageWithId:0 onPage:1];
  [self loadPageWithId:1 onPage:2];

  [scrollView addSubview:pageOneDoc];
  [scrollView addSubview:pageTwoDoc];
  [scrollView addSubview:pageThreeDoc];

  // adjust content size for three pages of data and reposition to center page
  scrollView.contentSize = CGSizeMake(960, 416);
  [scrollView scrollRectToVisible:CGRectMake(320,0,320,416) animated:NO];
}

- (void)loadPageWithId:(int)index onPage:(int)page 
{
  // load data for page
  switch (page) {
    case 0:
      pageOneDoc.text = [documentTitles objectAtIndex:index];
      break;
    case 1:
      pageTwoDoc.text = [documentTitles objectAtIndex:index];
      break;
    case 2:
      pageThreeDoc.text = [documentTitles objectAtIndex:index];
      break;
  }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)sender 
{
  // All data for the documents are stored in an array (documentTitles).
  // We keep track of the index that we are scrolling to so that we
  // know what data to load for each page.
  if(scrollView.contentOffset.x > scrollView.frame.size.width) 
  {
    // We are moving forward. Load the current doc data on the first page.
    [self loadPageWithId:currIndex onPage:0];

    // Add one to the currentIndex or reset to 0 if we have reached the end.
    currIndex = (currIndex $gt;= [documentTitles count]-1) ? 0 : currIndex + 1;
    [self loadPageWithId:currIndex onPage:1];

    // Load content on the last page. This is either from the next item in the array
    // or the first if we have reached the end.
    nextIndex = (currIndex $gt;= [documentTitles count]-1) ? 0 : currIndex + 1;

    [self loadPageWithId:nextIndex onPage:2];
  }
  if(scrollView.contentOffset.x $lt; scrollView.frame.size.width) {
    // We are moving backward. Load the current doc data on the last page.
    [self loadPageWithId:currIndex onPage:2];

    // Subtract one from the currentIndex or go to the end if we have reached the beginning.
    currIndex = (currIndex == 0) ? [documentTitles count]-1 : currIndex - 1;
    [self loadPageWithId:currIndex onPage:1];

    // Load content on the first page. This is either from the prev item in the array
    // or the last if we have reached the beginning.
    prevIndex = (currIndex == 0) ? [documentTitles count]-1 : currIndex - 1;

    [self loadPageWithId:prevIndex onPage:0];
  }     

  // Reset offset back to middle page
  [scrollView scrollRectToVisible:CGRectMake(320,0,320,416) animated:NO];
}

Answer 2

您不需要滚动视图来执行此操作；只需创建一个视图，其中并排排列 3 个子视图，然后添加平移手势识别器即可。

如果用户移动到右视图，则删除最左边的视图，在右侧添加一个视图，并使当前的右视图成为中心视图。您还需要对左视图执行类似的操作。