如何 Xamarin.Forms Scroll 使用 AbsoluteLayout

Question

我有这个.XAML 页面和滚动不起作用 当我删除绝对布局并采用堆栈布局时，它工作正常。

<ScrollView>
<AbsoluteLayout>
<ListView x:Name="lstView" ItemsSource="{Binding Items}" AbsoluteLayout.LayoutFlags="All" AbsoluteLayout.LayoutBounds="0,0,1,1"
ItemSelected="lstView_ItemSelected">
<ListView.Header>
<Label Text="Store Allocation" BackgroundColor="White" TextColor="Black" FontAttributes="Bold" HorizontalOptions="Fill" HorizontalTextAlignment="Center"  />
</ListView.Header>
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding Title}"  Height="200" Detail="{Binding Detail}" DetailColor="Black" TextColor="Red"  />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<BoxView AbsoluteLayout.LayoutFlags="All" AbsoluteLayout.LayoutBounds="0,0,1,1" BackgroundColor="LightGray" Opacity="0.7" InputTransparent="False" IsVisible="{Binding Path=IsBusy, Source={x:Reference Page}}" />
<ActivityIndicator IsRunning="{Binding Path=IsBusy, Source={x:Reference Page}}" AbsoluteLayout.LayoutFlags="PositionProportional" AbsoluteLayout.LayoutBounds=".5,.5,-1,-1" />
</AbsoluteLayout>
</ScrollView>

Answer 1

你的 XAML 基本上是"说">在页面上放一个ScrollView，用AbsoluteLayout填充该ScrollView。由于内部布局完全适合ScrollView因此无需滚动。此外，ListView和BoxView将采取整个AbsoluteLayout(AbsoluteLayout.LAyoutBounds="0,0,1,1")，不多不少。为什么ScrollView要滚动？

此外，如果它以这种方式工作，您将滚动ActivityIndicator和其他所有内容，这应该不是您想要的。我假设您想将ActivityIndicator保持在原位，在ListView之上。

您可以尝试的(我不是 100% 确定，但它应该有效)是仅用ScrollView包裹ListView并将ScrollView放入AbsoluteLayout中，这样，ScrollView将识别ListView对于屏幕来说太大并启用滚动，而其他一切都保持不变：

<AbsoluteLayout>
<ScrollView AbsoluteLayout.LayoutFlags="All" AbsoluteLayout.LayoutBounds="0,0,1,1">
<ListView x:Name="lstView" ItemsSource="{Binding Items}"
ItemSelected="lstView_ItemSelected">
<ListView.Header>
<Label Text="Store Allocation" BackgroundColor="White" TextColor="Black" FontAttributes="Bold" HorizontalOptions="Fill" HorizontalTextAlignment="Center"  />
</ListView.Header>
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding Title}"  Height="200" Detail="{Binding Detail}" DetailColor="Black" TextColor="Red"  />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ScrollView>
<BoxView AbsoluteLayout.LayoutFlags="All" AbsoluteLayout.LayoutBounds="0,0,1,1" BackgroundColor="LightGray" Opacity="0.7" InputTransparent="False" IsVisible="{Binding Path=IsBusy, Source={x:Reference Page}}" />
<ActivityIndicator IsRunning="{Binding Path=IsBusy, Source={x:Reference Page}}" AbsoluteLayout.LayoutFlags="PositionProportional" AbsoluteLayout.LayoutBounds=".5,.5,-1,-1" />
</AbsoluteLayout>

Answer 2

您也可以手动设置 AbsoluteLayout 的高度。

<ScrollView>
<AbsoluteLayout HeightRequest="800">
<!--Page Contents-->
</AbsoluteLayout>
</ScrollView>