扩展器不适用于Xamarin Forms MacOS吗

Question

我正在尝试实现Xamarin团队在MacOS上发布的新添加的Expander。

我遵循以下指南：Xamarin表格：如何将项目列表设置为Expander子项？

<StackLayout x:Name="expanderLayout" IsVisible="False" BindableLayout.ItemsSource="{Binding  AllItems,Mode=TwoWay}">
<BindableLayout.ItemTemplate>
<DataTemplate>
<Expander
ExpandAnimationEasing="{x:Static Easing.CubicIn}"
ExpandAnimationLength="500"
CollapseAnimationEasing="{x:Static Easing.CubicOut}"
CollapseAnimationLength="500">
<Expander.Header>
<Frame 
Padding="2"
Margin="5"
HasShadow="False"
BorderColor="#fdeec7"
CornerRadius="0">
<StackLayout
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand"
Orientation="Horizontal">
<Label 
Text="{Binding unit.title}"
TextColor="Black"
HorizontalOptions="Start" 
HorizontalTextAlignment="Start"
VerticalTextAlignment="Center"
VerticalOptions="CenterAndExpand">
<Label.FontSize>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>18</OnIdiom.Phone>
<OnIdiom.Tablet>36</OnIdiom.Tablet>
<OnIdiom.Desktop>18</OnIdiom.Desktop>
</OnIdiom>
</Label.FontSize>
</Label>
<StackLayout.Margin>
<OnIdiom x:TypeArguments="Thickness">
<OnIdiom.Phone>5</OnIdiom.Phone>
<OnIdiom.Tablet>8</OnIdiom.Tablet>
<OnIdiom.Desktop>5</OnIdiom.Desktop>
</OnIdiom>
</StackLayout.Margin>
<StackLayout.Padding>
<OnIdiom x:TypeArguments="Thickness">
<OnIdiom.Phone>5</OnIdiom.Phone>
<OnIdiom.Tablet>8</OnIdiom.Tablet>
<OnIdiom.Desktop>5</OnIdiom.Desktop>
</OnIdiom>
</StackLayout.Padding>
</StackLayout>
</Frame>
</Expander.Header>
<Expander.ContentTemplate>
<DataTemplate>
<StackLayout BindableLayout.ItemsSource="{Binding contentList,Mode=TwoWay}">
<BindableLayout.ItemTemplate>
<DataTemplate>
<StackLayout 
Orientation="Horizontal">
<Label
HorizontalOptions="Start"
Text="{Binding title}"
VerticalOptions="CenterAndExpand"     
TextColor="Black">
<Label.FontSize>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>16</OnIdiom.Phone>
<OnIdiom.Tablet>32</OnIdiom.Tablet>
<OnIdiom.Desktop>16</OnIdiom.Desktop>
</OnIdiom>
</Label.FontSize>
<Label.GestureRecognizers>
<TapGestureRecognizer
Tapped="LoadChapter"
CommandParameter="{Binding .}"
NumberOfTapsRequired="1">
</TapGestureRecognizer>
</Label.GestureRecognizers>
</Label>
</StackLayout>
</DataTemplate>
</BindableLayout.ItemTemplate>

</StackLayout>
</DataTemplate>
</Expander.ContentTemplate>
</Expander>
</DataTemplate>
</BindableLayout.ItemTemplate>
</StackLayout>

当导航到包含此代码的页面时，我得到一个异常，说明我需要调用Xamarin.Forms.Forms.SetFlags("Expander_Experimental");，我已经在MacOS文件夹中的public AppDelegate()方法中添加了它。

public AppDelegate()
{
Xamarin.Forms.Forms.SetFlags("Expander_Experimental");
Xamarin.Forms.Forms.SetFlags("CarouselView_Experimental");
var style = NSWindowStyle.Closable | NSWindowStyle.Miniaturizable | NSWindowStyle.Resizable | NSWindowStyle.Titled | NSWindowStyle.FullSizeContentView;
var frame = NSScreen.MainScreen.Frame;
var rect = NSWindow.FrameRectFor(frame, style);
_window = new NSWindow(rect, style, NSBackingStore.Buffered, false);
_window.MinSize = new CoreGraphics.CGSize(400, 300);
_window.TitlebarAppearsTransparent = true;
_window.MovableByWindowBackground = true;
_window.AccessibilityMinimized = false;
}

是MacOS不支持扩展器，还是我错过了关键的一步？

我也尝试在DidFinishLaunching方法中添加它，但没有区别。

public override void DidFinishLaunching(NSNotification notification)
{   
Xamarin.Forms.Forms.SetFlags("Expander_Experimental");
Xamarin.Forms.Forms.SetFlags("CarouselView_Experimental");
Forms.Init();
CachedImageRenderer.Init();
...

Answer 1

我在测试这个新组件时差点碰到它！如Xamarin.Forms实验标志页面所述：

永远不要多次调用SetFlags方法，因为后续调用将覆盖以前调用的结果。

所以不是：

Xamarin.Forms.Forms.SetFlags("Expander_Experimental");
Xamarin.Forms.Forms.SetFlags("CarouselView_Experimental"); // This call overwrites the `Expander_Experimental` flag set just above

调用一次，但同时使用两个标志：

Xamarin.Forms.Forms.SetFlags(new string[] { "Expander_Experimental", "CarouselView_Experimental" } );