在WPF中使用MVVM将n个矩形添加到画布

Question

我想在我的mvvm应用程序的主窗口中添加一组矩形.在我的viewModel中,我有一个对象集合,我用转换器转换为System.Windows.Shapes.Rectangle类(代码如下):

视图模型:

RecognizedValueViewModel 
{
    public ObservableCollection<BarcodeElement> BarcodeElements
    {
        get { return _BarcodeElements; }
        set { _BarcodeElements = value; }
    }

    public RecognizedValueViewModel()
    {
        BarcodeElements = InitializeBarcodeElements();
    }
}

转换器:

public BarcodeElementToRectangleConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        Rectangle barcodeRectangle = GetRectangleFromBarcodeElement(value as BarcodeElement);

        return barcodeRectangle;
    }
}

矩形应显示在MainWindow的画布中:

<Canvas x:Name="Canvas_Image_Main">
    <!-- Show rectangles here -->
</Canvas>

我会在代码中将Rectangles添加到canvas中,但我现在还没有在运行时有多少个矩形.我有办法实现这个目标吗？保护你.

Answer 1

在适当的MVVM方法中,您将拥有一个带有矩形列表的抽象表示的视图模型,例如:

public class RectItem
{
    public double X { get; set; }
    public double Y { get; set; }
    public double Width { get; set; }
    public double Height { get; set; }
}

public class ViewModel
{
    public ObservableCollection<RectItem> RectItems { get; set; }
}

然后,您将拥有一个使用ItemsControl可视化此类Rect项的集合的视图.ItemsControl将Canvas作为其ItemsPanel适当的ItemContainerStyle,ItemTemplate并且每个都绑定到适当的视图模型属性.它可能看起来像这样:

<ItemsControl ItemsSource="{Binding RectItems}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemContainerStyle>
        <Style TargetType="ContentPresenter">
            <Setter Property="Canvas.Left" Value="{Binding X}"/>
            <Setter Property="Canvas.Top" Value="{Binding Y}"/>
        </Style>
    </ItemsControl.ItemContainerStyle>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Rectangle Width="{Binding Width}" Height="{Binding Height}" Fill="Black"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

样式设置器中没有绑定的替代方法(在UWP中不起作用)可能如下所示:

<ItemsControl ItemsSource="{Binding RectItems}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Rectangle Width="{Binding Width}" Height="{Binding Height}" Fill="Black">
                <Rectangle.RenderTransform>
                    <TranslateTransform X="{Binding X}" Y="{Binding Y}"/>
                </Rectangle.RenderTransform>
            </Rectangle>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

Answer 2

您可以将矩形的集合绑定到ItemControl并设置其高度，宽度和边距：

<ItemsControl  ItemsSource="{Binding Path=RectangleCollection,Mode=TwoWay}">
    <ItemsControl.ItemTemplate>
        <DataTemplate >
            <Canvas>
                <Rectangle Stroke="Black" Heigth={some converter} Width={some converter} Margin={Some Converter}>
            </Canvas>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemControl>

只是一个让您入门的想法...