加正矩形与MVVM在WPF以帆布 [英] Add n rectangles to canvas with MVVM in WPF

问题描述

我想一组矩形添加到我的MVVM应用程序的主窗口。在我的ViewModel我有对象的集合，我转换为System.Windows.Shapes.Rectangle类用转换器（code以下）：

I want to add a set of rectangles to the main window of my mvvm application. In my viewModel I've got a collection of objects which I convert to System.Windows.Shapes.Rectangle classes with a converter (code below):

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;
    }
}

该矩形应显示在画布在我的主窗口：

The rectangles should be shown in a canvas in my MainWindow:

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

我想补充的矩形code到画布，但我现在有多少矩形在运行时有没有没有。有没有一种方法，我怎么能做到这一点？坦克你。

I would add Rectangles to canvas in code but I don't now how many rectangles are there at runtime. Is there a way how I can achieve this? Tank you.

推荐答案

在一个适当的MVVM方法，你将有矩形列表，例如一个抽象的重presentation视图模型像这样的：

In a proper MVVM approach you would have a view model with an abstract representation of a list of rectangles, e.g. like this:

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，你将不得不使用一个ItemsControl想象这样的矩形项目集合的视图。 ItemsControl的将有一个画布作为其 ItemsPanel 和适当的 ItemContainerStyle 和的ItemTemplate ，每个绑定到相应的视图模型属性。它可能是这样的：

Then you would have a view that uses an ItemsControl to visualize a collection of such Rect items. The ItemsControl would have a Canvas as its ItemsPanel and an appropriate ItemContainerStyle and ItemTemplate which each bind to the appropriate view model properties. It might look like this:

<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>

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