如何知道一个项目是否对用户可见? [英] How to know if an item is visible to user?

问题描述

请看这个:

<Grid>
    <ScrollViewer>
        <Grid Background="Red" Width="50" Height="50" VerticalAlignment="Top" Margin="0,-50,0,0"/>
    </ScrollViewer>
</Grid>

这里的红色网格由于其边距而不可见.但是当用户下拉时，它会在屏幕上可见.

here the red grid is not visible because of its margin. but when user pulls down, it will be visible on the screen.

我如何知道它何时可见?谢谢.

How can I know when it is visible? thanks.

(这是一个 WP8 应用程序，如果这很重要)

(It's a WP8 app, if that matters)

推荐答案

这个方法可能对你有用.

This method might come handy for you.

private bool IsUserVisible(FrameworkElement element, FrameworkElement container)
{
    if (!element.IsVisible)
        return false;

    Rect bounds = element.TransformToAncestor(container).TransformBounds(new Rect(0.0, 0.0, element.ActualWidth, element.ActualHeight));
    Rect rect = new Rect(0.0, 0.0, container.ActualWidth, container.ActualHeight);
    return rect.Contains(bounds.TopLeft) || rect.Contains(bounds.BottomRight);
}

这篇关于如何知道一个项目是否对用户可见?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！