Xamarin.Forms 绑定指定的强制转换无效
我有一个奇怪的异常,编译器告诉我指定的强制转换无效,即使我所做的很简单.
I have a weird exception where the Compiler tells me that the Specified cast is not valid even though what im doing is very Simple.
我有一个绑定到 ObservableCollection 的 ListView.在我的 Listview 里面是一个带有网格的 ViewCell.Xamarin.Forms 版本 2.3.2.127
I have a ListView binded to a ObservableCollection. And inside my Listview is a ViewCell with a Grid. Xamarin.Forms Version 2.3.2.127
<ListView ItemsSource="{Binding GiftCollection}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.View>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="20"/>
<RowDefinition Height="20"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="40"/>
</Grid.ColumnDefinitions>
<Label Grid.Row="0" Grid.Column="0" Text="{Binding GiftName}"/>
<Label Grid.Row="1" Grid.Column="0" Text="{Binding GiftDescription}"/>
<Image Grid.Row="0" Grid.RowSpan="2" Grid.Column="1" Source="{Binding GiftImage}"/>
</Grid>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
型号:
public class GiftModel {
public string GiftName { get; set; }
public string GiftDescription { get; set; }
public ImageSource GiftImage { get; set; }
}
视图模型:
public class NextRoundViewModel : BaseViewModel {
public NextRoundViewModel(ApplicationModel applicationModel) {
ApplicationModel = applicationModel;
Initialize();
}
public ApplicationModel ApplicationModel { get; set; }
public ObservableCollection<GiftModel> GiftCollection { get; set; }
public string CurrentRound => "Runde 2";
private void Initialize() {
GiftCollection = new ObservableCollection<GiftModel> {
new GiftModel {
GiftName = "100 Punkte",
GiftDescription = "Test",
GiftImage = ImageSource.FromFile("Star.png"),
},
new GiftModel {
GiftName = "200 Punkte",
GiftDescription = "Test",
GiftImage = ImageSource.FromFile("Star.png"),
},
new GiftModel {
GiftName = "300 Punkte",
GiftDescription = "Test",
GiftImage = ImageSource.FromFile("Star.png"),
},
};
}
}
所以我尝试了所有方法,但是如果我使用例如 TextCell,则异常消失了.System.InvalidCastException:指定的强制转换无效.这很奇怪,因为我不知道去哪里寻找 Bug.
So ive tried everything but if i use for example a TextCell the Exception is gone. System.InvalidCastException: Specified cast is not valid. It is just weird because i dont know where to look for the Bug.
我也遇到了这个问题,问题出在 xaml
上.我的 <DataTemplate>
里面有一个
,你可以删除你的
,这应该可以解决问题.
I had this problem too, the issue was with the xaml
. I had a <StackLayout>
inside of my <DataTemplate>
, you can remove your <Grid>
and that should solve the problem.
您是否知道可以将
替换为
:
Did you know that you could replace the <Grid>
with an <ImageCell>
:
<ListView.ItemTemplate>
<DataTemplate>
<ImageCell
Text="{Binding GiftName}"
Detail="{Binding GiftDescription}"
ImageSource="{Binding GiftImage}">
</ImageCell>
</DataTemplate>
</ListView.ItemTemplate>