Instagram式导航栏（iOS 7）

Question

我正试图产生同样的效果，因为Instagram在标题中有。我怎么能这样做？

我尝试了很多解决方案。

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

但它有一个大问题 - 它正在使用uipangesturerecognizer移动吧。这对我来说很糟糕，因为如果桌子位于顶部，我想要显示条形图。

我试图改变这个控件的工作来滚动视图委托，但是发现了很多问题，有什么想法，他们是怎么做到的？

Answer 1

我找到了解决方案，就像你说的那样 - 你必须稍微处理滚动视图委托，但是经过大约2个小时后我才知道这一切。我试图解决的问题是能够像在Instagram中那样在一个连续的动作中获得标题。

因此，首先检查xib设置，它有一个标题视图（0 20,320 85），它位于（0 20,320 548）表视图的正后方

所以这是启动后的样子（黄色的表视图框）：

这是我想要它在拉下后的样子（标题框架为红色）：

所以我只是粘贴带注释的代码，我希望它足够容易理解。

进行定义

#define SIGNIFICANT_SCROLLING_DISTANCE 200

创建两个属性

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

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;
}

享受光滑的桌面在屏幕上来回滚动=） 这也可以修改，您可以添加和调整标题大小，使其基本上与Instagram相同。

Answer 2

将AMScrollingNavbar与tableViewController一起使用，并覆盖willDisplayCell方法以显示表格是否滚动到顶部：

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

Answer 3

您可以在班级中使用下面提到的方法，在Instagram中为导航栏添加效果。

- (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，将其添加到视图控制器：

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