使用分页旋转 UIScrollView 的问题答案

【问题标题】：problems rotating UIScrollView with paging使用分页旋转 UIScrollView 的问题
【发布时间】：2010-08-29 17:21:21
【问题描述】：

在处理旋转时，我在 iPhone 上使用 UIScrollView 时遇到问题。我使用 Apple 的 PageControl 示例作为模型，但我自己在 View 中创建滚动视图。

1) 在默认纵向加载时，滚动视图按预期工作，从左到右水平滚动

2) 开箱即用，当顺时针旋转并重新初始化时，大部分情况下会将其侧向旋转，现在它垂直向下旋转，而不是所需的水平静止。似乎滚动视图框架的宽度/高度没有改变，只是自身的方向。

3) 我尝试添加一些方向检测逻辑，以根据方向正确调整滚动视图的大小和分页，但前提是我将 CCW 旋转为横向。如果我去 CW，它会从右边开始，然后滚动到左边，事情就不起作用了。

很明显，这越来越不自然了，那么有没有合适的方法来设置我的 UIScrollview 并通过旋转重新初始化它，使其始终从左到右滚动？


- (void)loadView {
    [self setupPage];
}

-(void) setupPage {
  // lazy init view controllers
  NSMutableArray *controllers = [[NSMutableArray alloc] init];
    for (unsigned i = 0; i = kNumberOfPages) return;

    // replace the placeholder if necessary
    MyViewController *controller = [viewControllers objectAtIndex:page];
    if ((NSNull *)controller == [NSNull null]) {
        controller = [[MyViewController alloc] initWithPageNumber:page];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];
    }

    // add the controller's view to the scroll view
    if (nil == controller.view.superview) {
        CGRect frame = scrollView.frame;

        int x = 0;
        int y = 0;
        UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];
        if(orientation == UIDeviceOrientationLandscapeLeft || orientation == UIDeviceOrientationLandscapeRight){
            x = 0;
            y = frame.size.height * page; 
        } else {
            x = frame.size.width * page;
            y = 0;
        }

        frame.origin.x = x;
        frame.origin.y = y;
        controller.view.frame = frame;
        [scrollView addSubview:controller.view];
    }
}

- (void)scrollViewDidScroll:(UIScrollView *)sender {
    // We don't want a "feedback loop" between the UIPageControl and the scroll delegate in
    // which a scroll event generated from the user hitting the page control triggers updates from
    // the delegate method. We use a boolean to disable the delegate logic when the page control is used.
    if (pageControlUsed) {
        // do nothing - the scroll was initiated from the page control, not the user dragging
        return;
    }

    // Switch the indicator when more than 50% of the previous/next page is visible
    CGFloat pageWidth = scrollView.frame.size.width;
    int offset = 0;
    UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];
    if(orientation == UIDeviceOrientationLandscapeLeft || orientation == UIDeviceOrientationLandscapeRight){
        pageWidth = scrollView.frame.size.height;
        offset = scrollView.contentOffset.y; 
    } else {
        pageWidth = scrollView.frame.size.width;
        offset = scrollView.contentOffset.x ;
    }

    //CGFloat pageWidth = scrollView.frame.size.width;
    int page = floor((offset - pageWidth / 2) / pageWidth) + 1;
    pageControl.currentPage = page;

    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
    [self loadScrollViewWithPage:page - 1];
    [self loadScrollViewWithPage:page];
    [self loadScrollViewWithPage:page + 1];

    // A possible optimization would be to unload the views+controllers which are no longer visible
}

// At the begin of scroll dragging, reset the boolean used when scrolls originate from the UIPageControl
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    pageControlUsed = NO;
}

// At the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    pageControlUsed = NO;
}


- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation 
{
    [self setupPage];
}

【问题讨论】：

标签： iphone objective-c uikit rotation

【解决方案1】：

你没有改变你的滚动视图的 contentSize，所以当它旋转时它不知道它的宽度大于它的高度。

另外，作为快捷方式，每个 VC 都已经设置了 interfaceOrientation 属性，并且内置了检测方向的函数：UIInterfaceOrientationIsPortrait(self.interfaceOrientation) 和 UIInterfaceOrientationIsLandscape(self.interfaceOrientation)。

最后，只是视觉上的东西，使用 willRotateToInterfaceOrientation:duration 对眼睛来说更好一些，并且用户永远不会感知到变化，因为它几乎与旋转同时发生。

【讨论】：