问题描述
我正在使用 Xamarin Forms 集合视图,此集合视图内是工具包扩展器,当有人单击标题时,我已绑定命令,在此命令中,我试图在扩展器的网格内填充列表视图,请参阅代码下面:
<CollectionView x:Name="MathList" HeightRequest="320" SelectionChanged="MathList_SelectionChanged">
<CollectionView.ItemTemplate>
<DataTemplate>
<xct:Expander Command="{Binding GetMathSubCatgories}">
<xct:Expander.Header>
<Frame Padding="10" Margin="10" HasShadow="False" BorderColor="LightGray" VerticalOptions="CenterandExpand">
<StackLayout Orientation="Horizontal">
<Image Source="{Binding icon}" WidthRequest="25" HeightRequest="25"></Image>
<Label Text="{Binding name}" TextColor="{Binding textColor}" FontSize="Large" FontAttributes="Bold" HeightRequest="35" VerticalOptions="CenterandExpand"></Label>
</StackLayout>
</Frame>
</xct:Expander.Header>
<Grid Padding="10">
<Grid.ColumnDeFinitions>
<ColumnDeFinition Width="Auto" />
</Grid.ColumnDeFinitions>
<ListView x:Name="SubCatgories" ItemsSource="{Binding subTaskClass}">
<ListView.ItemTemplate>
<DataTemplate>
<StackLayout>
<Frame Padding="10" Margin="10" HasShadow="False" BorderColor="LightGray" VerticalOptions="CenterandExpand">
<StackLayout Orientation="Horizontal">
<Label Text="aaa" FontAttributes="Bold" HeightRequest="35" VerticalOptions="CenterandExpand"></Label>
</StackLayout>
</Frame>
</StackLayout>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</xct:Expander>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
但是在我后面的代码中,当我尝试像这样填充列表视图时:
public ICommand GetMathSubCatgories => new Command(() =>
{
Console.Write("Here");
GetSubTasks(taskcategoryid);
});
public async void GetSubTasks(int taskcategory)
{
SubCatgories.ItemsSource = await webService.GetMathSubTasks(taskcategory);
}
它说 SubCatgories 不可用。我将如何在数据集合中填充列表视图。
这个方法我也试过,还是不行:
<CollectionView x:Name="MathList" HeightRequest="320" SelectionChanged="MathList_SelectionChanged">
<CollectionView.ItemTemplate>
<DataTemplate>
<xct:Expander Command="{Binding GetMathSubCatgories}">
<xct:Expander.Header>
<Frame Padding="10" Margin="10" HasShadow="False" BorderColor="LightGray" VerticalOptions="CenterandExpand">
<StackLayout Orientation="Horizontal">
<Image Source="{Binding icon}" WidthRequest="25" HeightRequest="25"></Image>
<Label Text="{Binding name}" TextColor="{Binding textColor}" FontSize="Large" FontAttributes="Bold" HeightRequest="35" VerticalOptions="CenterandExpand"></Label>
</StackLayout>
</Frame>
</xct:Expander.Header>
<Grid Padding="10">
<Grid.ColumnDeFinitions>
<ColumnDeFinition Width="Auto" />
</Grid.ColumnDeFinitions>
<ListView x:Name="SubCatgories" ItemsSource="{Binding subCategories}">
<ListView.ItemTemplate>
<DataTemplate>
<StackLayout>
<Frame Padding="10" Margin="10" HasShadow="False" BorderColor="LightGray" VerticalOptions="CenterandExpand">
<StackLayout Orientation="Horizontal">
<Label Text="{Binding name}" FontAttributes="Bold" HeightRequest="35" VerticalOptions="CenterandExpand"></Label>
</StackLayout>
</Frame>
</StackLayout>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</xct:Expander>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
这是我用于 collectionView 的类
public class TaskClass
{
WebServiceClass webService = new WebServiceClass();
List<SubTaskClass> subTasks = new List<SubTaskClass>();
public int taskcategoryid { get; set; }
public string type { get; set; }
public string name { get; set; }
public string icon { get; set; }
public int sortOrder { get; set; }
public string textColor
{
get
{
if (name == "Addition")
{
return "#02cc9d";
}
else if (name == "Subtraction")
{
return "black";
}
else if (name == "Divison")
{
return "#fa5156";
}
else
{
return "#23a0b6";
}
}
}
public List<SubTaskClass> subCategories
{
get
{
GetSubTasks(taskcategoryid);
return subTasks;
}
}
public async void GetSubTasks(int taskcategory)
{
subTasks = await webService.GetMathSubTasks(taskcategory);
}
}
这里是子任务类:
public class SubTaskClass
{
public int id { get; set; }
public int taskcategory { get; set; }
public string name { get; set; }
}