Xamarin 绑定功能作为具有数据绑定的 Listview 内的图像源

Question

我正在尝试在下面的 ListView 中可视化一个名为 MinRepresentation 的对象的状态。

我想绑定函数ImageSource stateImage(MinRepresentationState state)，在这里我切换状态并取回Imagesource。

我的问题是，访问函数并通过 xaml 传递参数。

Visible Orders 是 MinRepresentation 的集合，每个都包含 State

<ListView HasUnevenRows="True" SelectionMode="Single" ItemsSource="{Binding VisibleOrders}" ItemSelected="OnListViewItemSelected" ItemTapped="OnListViewItemTapped">

***OTHER STUFF***

<StackLayout Orientation="Horizontal" Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="3" Padding= "0,5,0,5" BackgroundColor="#CC3F6E3F">

<Image Source="{Binding stateImage(State)" Margin="10,0,0,0" />

<Label Text="{Binding Id, StringFormat='ID: [{0}]'}" FontSize="Small" Margin="5,0,0,0" FontAttributes="Bold" TextColor="#FFFFFF"/>

</StackLayout>

***OTHER STUFF***

</ListView>

public ImageSource stateImage(MinRepresentationState state)
        {

            switch (state)
            {
                case MinRepresentationState.Assigned:
                    return ImageSource.FromResource("state_assigned.png");
            }
        }

Answer 1

您只能绑定到公共属性。在模型上创建 StateImage 属性

public string StateImage 
{
  get {
    switch (State)
    {
      case MinRepresentationState.Assigned:
        return "state_assigned.png";
    }
  }
}

Answer 2

您还可以使用 DataTrigger 在 XAML 中设置图像

<Image Source="state_default.png" Margin="10,0,0,0">
    <Image.Triggers>
        <DataTrigger TargetType="Image" Binding="{Binding State}" Value="Assigned">
            <Setter Property="Source" Value="state_assigned.png" />
        </DataTrigger>
    </Image.Triggers>
</Image>

参考：https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/triggers#data

Answer 3

您可以使用IValueConverter 来实现这一点。创建一个IValueConverter 类并将您的逻辑代码放在那里：

public class StateToImageConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        MinRepresentationState representationState = (MinRepresentationState)value;
        if (representationState == MinRepresentationState.Assigned)
        {
            return "state_assigned.png";
        }
        return "otherImage.png";
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

然后像这样在 XAML 中使用它：

<!--Define it in resources-->
<ContentPage.Resources>
    <local:StateToImageConverter x:Key="StateToImageConverter"/>
</ContentPage.Resources>

<!--Use converter-->
<Image Source="{Binding State, Converter={StaticResource StateToImageConverter}}" Margin="10,0,0,0"/>