隐藏navigationBar

Question

我有一些不明白的问题。

我想把我的导航栏藏在我的滚动条上，我做了两个不同的解决方案：

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    lastOffsetY = scrollView.contentOffset.y;
}

- (void) scrollViewWillBeginDecelerating:(UIScrollView *)scrollView {
    bool hide = (scrollView.contentOffset.y > lastOffsetY);
    [[self navigationController] setNavigationBarHidden:hide animated:YES];

    NSLog(@"%f %f %f %f", self.navigationController.navigationBar.frame.origin.y, self.navigationController.navigationBar.layer.frame.origin.y, self.webView.frame.origin.y, self.view.superview.frame.origin.y);
}

或者第二种解决方案：

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGRect frame = self.navigationController.navigationBar.frame;
    CGFloat size = frame.size.height - 21;
    CGFloat framePercentageHidden = ((20 - frame.origin.y) / (frame.size.height - 1));
    CGFloat scrollOffset = scrollView.contentOffset.y;
    CGFloat scrollDiff = scrollOffset - lastOffsetY;
    CGFloat scrollHeight = scrollView.frame.size.height;
    CGFloat scrollContentSizeHeight = scrollView.contentSize.height + scrollView.contentInset.bottom;

    if (scrollOffset <= -scrollView.contentInset.top) {
        frame.origin.y = 20;
    } else if ((scrollOffset + scrollHeight) >= scrollContentSizeHeight) {
        frame.origin.y = -size;
    } else {
        frame.origin.y = MIN(20, MAX(-size, frame.origin.y - scrollDiff));
    }

    [self.navigationController.navigationBar setFrame:frame];

    [self updateBarButtonItems:(1 - framePercentageHidden)];
    lastOffsetY = scrollOffset;


    [self.view setNeedsUpdateConstraints];
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self stoppedScrolling];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView
                  willDecelerate:(BOOL)decelerate
{
    if (!decelerate) {
        [self stoppedScrolling];
    }
}

- (void)stoppedScrolling
{
    CGRect frame = self.navigationController.navigationBar.frame;
    if (frame.origin.y < 20) {
        [self animateNavBarTo:-(frame.size.height - 21)];
    }

    NSLog(@"%f %f %f %f", self.navigationController.navigationBar.frame.origin.y, self.navigationController.navigationBar.layer.frame.origin.y, self.webView.frame.origin.y, self.view.superview.frame.origin.y);
}

- (void)updateBarButtonItems:(CGFloat)alpha
{
    [self.navigationItem.leftBarButtonItems enumerateObjectsUsingBlock:^(UIBarButtonItem* item, NSUInteger i, BOOL *stop) {
        item.customView.alpha = alpha;
    }];
    [self.navigationItem.rightBarButtonItems enumerateObjectsUsingBlock:^(UIBarButtonItem* item, NSUInteger i, BOOL *stop) {
        item.customView.alpha = alpha;
    }];
    self.navigationItem.titleView.alpha = alpha;
    self.navigationController.navigationBar.tintColor = [self.navigationController.navigationBar.tintColor colorWithAlphaComponent:alpha];
}

- (void)animateNavBarTo:(CGFloat)y
{
    [UIView animateWithDuration:0.2 animations:^{
        CGRect frame = self.navigationController.navigationBar.frame;
        CGFloat alpha = (frame.origin.y >= y ? 0 : 1);
        frame.origin.y = y;
        [self.navigationController.navigationBar setFrame:frame];
        [self updateBarButtonItems:alpha];
    }];
}

首先，导航条动画很棒，webView在我的屏幕上，状态栏在webView下面，这不是很好。

第二种情况是，导航条正确地执行动画，我的状态栏有正确的背景，但是我的webView保持静态，在navigationBar老位置下有一个白色背景，而webView不跟随我的导航栏。

我的问题是，我怎样才能使像setNavigationBarHidden苹果功能？

谢谢

Answer 1

我大概知道你想要什么样的动画。

对于第二个解决方案，还需要更改UIWebView的UIWebView属性。

// get UIWebView frame here
CGRect webViewRect = _webView.frame;

if (scrollOffset <= -scrollView.contentInset.top) {
    frame.origin.y = 20;
} else if ((scrollOffset + scrollHeight) >= scrollContentSizeHeight) {
    frame.origin.y = -size;
} else {
    frame.origin.y = MIN(20, MAX(-size, frame.origin.y - scrollDiff));
}
webViewRect.origin.y = frame.origin.y + frame.size.height;

if ( webViewRect.origin.y != _webView.frame.origin.y ) {
    [_webView setFrame:webViewRect];
}

我没有您的视图体系结构的完整图片，但是如果通过将_webView向上移动，_webView在底部的长度太短，您可以增加_webView的高度，相当于导航条的高度，并将其内容嵌入到导航栏的底部边缘，即导航栏的高度。就像这样：

_webView = [[UIWebView alloc] initWithFrame:CGRectMake(0.0, 0.0, self.view.bounds.size.width, self.view.bounds.size.height+self.navigationController.navigationBar.frame.size.height)];
[_webView.scrollView setContentInset:UIEdgeInsetsMake(0.0, 0.0, self.navigationController.navigationBar.frame.size.height, 0.0)];