类似 Instagram 的导航栏 (iOS 7)

Question

我正在尝试产生与 instagram 标题中相同的效果。我该怎么做？

我尝试了很多解决方案。

最佳 - https://github.com/andreamazz/AMScrollingNavbar

但它有一个大问题 - 它使用 uipangesturerecognizer 移动条。这对我很不利，因为如果桌子在顶部，我想显示栏。

我尝试将此控件的工作更改为滚动视图委托，但发现它有很多问题，您有什么想法，他们是如何做到的？

Answer 1

我找到了解决方案，就像你说的那样 - 你必须稍微弄乱滚动视图委托，但大约 2 小时后我就搞定了。我试图解决的问题是能够像在 Instagram 中那样以一个连续的动作将标题取出。

所以，首先检查 xib 设置，它在 (0 20, 320 85) 处有一个标题视图，它位于 (0 20, 320 548) 处的表视图后面

这是启动后的样子（黄色的表格视图框架）：

这是我希望它在下拉后的样子（红色标题框）：

所以我只是用 cmets 粘贴代码，我希望它可以理解。

定义

#define SIGNIFICANT_SCROLLING_DISTANCE 200

创建两个属性

@property (nonatomic) CGFloat lastScrollViewOffsetY;
@property (nonatomic) CGFloat distancePulledDownwards;

比为scrollViewDidScroll委托方法添加以下实现

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    // store current scroll view frame as we will change it later on and set it
    // back to the scroll view in the very end
    CGRect currentScrollViewRect = scrollView.frame;
    // same with the content offset
    CGPoint currentScrollViewOffset = scrollView.contentOffset;
    CGFloat offsetShiftY = self.lastScrollViewOffsetY - scrollView.contentOffset.y;

    if (offsetShiftY > 0) {
        // pulling downwards
        // keep trrack of the distance that we pulled downwards
        self.distancePulledDownwards += offsetShiftY;

        // header opens (table view shifts its frame down) in two cases:
        // 1. contentOffset.y<0
        // 2. scrolled downwards a significant amount or header is already open
        // but in both cases we have to make sure that it doesn't open further than we want it to
        CGFloat wantedOriginY = currentScrollViewRect.origin.y;
        if ((scrollView.contentOffset.y<0) || (self.distancePulledDownwards > SIGNIFICANT_SCROLLING_DISTANCE) || (currentScrollViewRect.origin.y>20)){

            // shift scroll views frame by offset shift
            wantedOriginY = currentScrollViewRect.origin.y + offsetShiftY;
            // compensate that shift by moving content offset back
            currentScrollViewOffset.y += (wantedOriginY <= 105) ? offsetShiftY : 0;
        }
        currentScrollViewRect.origin.y = (wantedOriginY <= 105) ? wantedOriginY : 105;

    }
    else {
        // pulling upwards
        self.distancePulledDownwards = 0;

        // header closes (table view shifts its frame up) in one case: when it is open =) (and contentOffset.y>0 to eliminate closing on bounce)
        if (scrollView.contentOffset.y > 0) {
            CGFloat wantedOriginY = currentScrollViewRect.origin.y + offsetShiftY;
            currentScrollViewRect.origin.y = (wantedOriginY >= 20) ? wantedOriginY : 20;
            currentScrollViewOffset.y += (wantedOriginY >= 20) ? offsetShiftY : 0;
        }
    }

    // set the changed (if it was changed at all) frame to the scroll view
    [scrollView setFrame:currentScrollViewRect];

    // correct offset using a special trick
    // it ensures that scrollViewDidScroll: won't be called on setting the offset
    scrollView.delegate = nil;
    [scrollView setContentOffset:currentScrollViewOffset];
    scrollView.delegate = self;

    // and finally remember the current offset as the last
    self.lastScrollViewOffsetY = scrollView.contentOffset.y;
}

并享受您在屏幕上来回滚动的流畅表格 =) 这也可以修改，您可以添加和调整标题，使其与 Instagram 基本相同。

Answer 2

在 tableViewController 中使用 AMScrollingNavbar 并覆盖 willDisplayCell 方法以在表格滚动到顶部时显示栏：

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row == 0) {
        [self showNavbar];
    }
}

Answer 3

您可以在您的课程中使用下面提到的方法，在其中您想要在导航栏上添加效果，就像在 Instagram 中一样。

- (void)scrollViewDidScroll:(UIScrollView *)sender {
//Initializing the views and the new frame sizes.
UINavigationBar *navbar =self.navigationController.navigationBar;
UIView *tableView = self.view;
CGRect navBarFrame = self.navigationController.navigationBar.frame;

CGRect tableFrame = self.view.frame;

//changing the origin.y based on the current scroll view.
//Adding +20 for the Status Bar since the offset is tied into that.

if (isiOS7) {
     navBarFrame.origin.y = MIN(0, MAX(-44, (sender.contentOffset.y * -1)))  +20 ;
     tableFrame.origin.y = navBarFrame.origin.y + navBarFrame.size.height;
}else{
    navBarFrame.origin.y = MIN(0, (sender.contentOffset.y * -1)) +20;
    tableFrame.origin.y = MIN(0,MAX(-44,(sender.contentOffset.y * -1))) ;
}

navbar.frame = navBarFrame;
tableView.frame = tableFrame;

}

Answer 4

使用该库，将其添加到您的视图控制器：

- (BOOL)scrollViewShouldScrollToTop {
    [self showNavbar];
    return YES;
}