NSScrollView检测滚动位置 [英] NSScrollView detect scroll position

问题描述

当底部滚动时如何检测位置滚动？

How can i detect scroll of position when the scroll at bottom?

[[_scrollView contentView] setPostsBoundsChangedNotifications:YES];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(boundsDidChangeNotification:)
                                             name:NSViewBoundsDidChangeNotification
                                           object:[_scrollView contentView]];





- (void) boundsDidChangeNotification: (NSNotification *) notification
{
    NSPoint currentScrollPosition = [[_scrollView contentView] bounds].origin;
}

推荐答案

更新：

我最初的答案是完全错误的。

感谢JWWalker和Wil Shipley通过评论使我意识到了这一点。

Update:
My original answer was plain wrong.
Thanks to JWWalker and Wil Shipley for making me aware of that via comments.

对于希望通过搜索来到这里的人们来说，这是一个更有希望的答案：

与 UIScrollView 不同， NSScrollView 不提供委托方法来通知您何时视图滚动到顶部/底部。

要检测到这些情况，必须启用 boundsDidChange 通知并订阅。

Here's a hopefully more helpful answer for people coming here via search:
Unlike UIScrollView, NSScrollView does not provide a delegate method to inform you when a view was scrolled to top/bottom.
To detect those situations, you have to enable boundsDidChange notifications and subscribe to them.

收到边界更新时，您可以检查剪辑视图边界的 y 坐标是否为 0 （=底部），或者剪辑视图边界的上边缘与文档视图（=顶部）对齐。

When receiving a bounds update, you can check if the y coordinate of the clip view bounds is 0 (= bottom), or if the top edge of the clip view bounds aligns with the document view (= top).

private func configureScrollView() {
        self.scrollView.contentView.postsBoundsChangedNotifications = true
        NotificationCenter.default.addObserver(self, selector: #selector(contentViewDidChangeBounds), name: NSView.boundsDidChangeNotification, object: self.scrollView.contentView)
    }

@objc
func contentViewDidChangeBounds(_ notification: Notification) {
    guard let documentView = scrollView.documentView else { return }

    let clipView = scrollView.contentView
    if clipView.bounds.origin.y == 0 {
        print("bottom")
    } else if clipView.bounds.origin.y + clipView.bounds.height == documentView.bounds.height {
        print("top")
    }
}

对于使用弹性滚动的滚动视图，更新会短暂延迟，因为剪辑视图似乎将边界更改通知推迟到滚动弹跳完成之前。

For scroll views that use elastic scrolling, the updates come with a short delay because the clip view seems to defer the bounds change notifications until the scroll bounce has finished.

您可以使用<$ c $的可见矩形c> NSScrollView 的contentView而不是范围：

You can use the visible rect of your NSScrollView's contentView instead of the bounds:

- (void)boundsDidChangeNotification:(NSNotification*) notification
{
    NSRect visibleRect = [[_scrollView contentView] documentVisibleRect];
    NSLog(@"Visible rect:%@", NSStringFromRect(visibleRect));
    NSPoint currentScrollPosition = visibleRect.origin;
}

内容视图范围在滚动过程中不会改变，因此在原始代码中，bounds.origin可能始终返回0/0。

The content view bounds don't change during scrolling, so in your original code, the bounds.origin probably always returns 0/0.

这篇关于NSScrollView检测滚动位置的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！