Xamarin Forms CollectionView 自定义布局设计 [英] Xamarin Forms CollectionView Custom Layout Design

问题描述

在我设计的应用程序中，我使用 collectionview 来显示大量图像.这是我目前的设计.

In the app that I'm designing, I use collectionview to show loads of images. And this is my current design.

这就是我想要的设计.高度较短的图像将使下一个图像填充空白.

And this is the design I want. where the images that are shorter in height will have the next image fill up the white spaces.

这是我的代码:

            <CollectionView x:Name="cv_WallPapers"
                            ItemsSource="{Binding Results, Mode=TwoWay}"
                            HorizontalOptions="FillAndExpand"
                            VerticalOptions="FillAndExpand"
                            Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2"
                            SelectionMode="Single"
                            SelectionChanged="cv_WallPapers_SelectionChanged"
                            >
                <CollectionView.ItemsLayout>
                    <GridItemsLayout Orientation="Vertical"
                                     Span="2"
                                     VerticalItemSpacing="5"
                                     HorizontalItemSpacing="5"/>
                </CollectionView.ItemsLayout>
                <CollectionView.ItemTemplate>
                    <DataTemplate>

                        <Frame Padding="4"
                               BorderColor="#34eba8"
                               BackgroundColor="#34eba8"
                               CornerRadius="10"
                               HasShadow="False">
                            <Image Source="{Binding urls.regular}"
                                   HorizontalOptions="FillAndExpand"/>
                        </Frame>

                    </DataTemplate>
                </CollectionView.ItemTemplate>
            </CollectionView>

我不知道如何在 Xamarin 中做到这一点.并感谢您的帮助！

I've no idea how to do that in Xamarin. And appreciate the help!

推荐答案

很遗憾，Forms 中的CollectionView 直到现在仍然不支持这样的布局.但是，我们可以使用自定义渲染器作为解决方法在安卓中.

Unfortunately，CollectionView in Forms still doesn't support such a layout until now .However, we could use Custom Renderer as a workaround in Android.

public class MyCollectionViewRenderer: CollectionViewRenderer
{
    public MyCollectionViewRenderer(Context context) : base(context)
    {

    }

    protected override void OnElementChanged(ElementChangedEventArgs<ItemsView> elementChangedEvent)
    {
        base.OnElementChanged(elementChangedEvent);

        if(elementChangedEvent.NewElement!=null)
        {
            this.SetLayoutManager(new StaggeredGridLayoutManager(2, 1));
        }

    }
}

在iOS中，由于iOS原生的UICollectionView没有这样的属性或API，所以需要手动实现(重新计算每个item的大小并设置偏移量).您可以参考 https://developer.apple.com/documentation/uikit/uicollectionview/customizing_collection_view_layouts?language=objc.我会尽快发布功能请求.

In iOS , because the UICollectionView in native iOS doesn't have such a property or API , so we need to implement it manually (re-calculate the size of each item and set the offset) . Which you could refer https://developer.apple.com/documentation/uikit/uicollectionview/customizing_collection_view_layouts?language=objc . And I will post the feature request as soon as possible .

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