zoukankan      html  css  js  c++  java
  • WPF Canvas, how to add children dynamically with MVVM code behind

    reference website : https://stackoverflow.com/questions/5913792/wpf-canvas-how-to-add-children-dynamically-with-mvvm-code-behind

    Requirement:

    To draw one Bitmap Image and rectangle(s) based on the collection of points. The rectangle should exactly fit on the pixels location over the image. There is also some text need to be added inside the rectangle.

    The Image will be always only one and the rectangles will be dynamically added.

    Current Solution:

    Have a canvas with Image Control. Add the the dynamic code under the code behind file ViewImageResult.xaml.cs.

        private void DrawResult(int left, int right, int width, int height)
        {
            Border bord = new Border();
            bord.BorderThickness = new Thickness(1);
            bord.BorderBrush = Brushes.Red;
            bord.Width = width;
            bord.Height = height;
            _mainCanvas.Children.Add(bord);
            Canvas.SetLeft(bord, left);
            Canvas.SetTop(bord, right);
        }
    

    Issue:

    Since i follow MVVM pattern, the collection of points for rectangle is in my ViewModel file ViewImageResultModel.cs. I am not able to add the child rectangle dynamically from the ViewModel file.

    2 Answers

    48
     

    ItemsControl is your friend:

    <Grid>
        <Image Source="..."/>
        <ItemsControl ItemsSource="{Binding Points}">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <Canvas/>
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
            <ItemsControl.ItemContainerStyle>
                <Style>
                    <Setter Property="Canvas.Left" Value="{Binding X}"/>
                    <Setter Property="Canvas.Top" Value="{Binding Y}"/>
                </Style>
            </ItemsControl.ItemContainerStyle>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Border BorderBrush="Red" BorderThickness="1" Width="{Binding Width}" Height="{Binding Height}"/>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </Grid>
    

    The above assumes your VM exposes a collection of points via a Points property, and that each point VM has XYWidth, and Height properties.

    • 2
      Many Thanks Kent. That works fabulous with small change <Canvas IsItemsHost="True" />   Jun 13 '11 at 10:30
    • 2
      That... that is just beautiful.   Feb 28 '12 at 8:54
     
    0

    Added IsItemsHost="True" to the Canvas of Kent's solution:

    <Grid>
        <Image Source="..."/>
        <ItemsControl ItemsSource="{Binding Points}">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <Canvas  IsItemsHost="True"/>
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
            <ItemsControl.ItemContainerStyle>
                <Style>
                    <Setter Property="Canvas.Left" Value="{Binding X}"/>
                    <Setter Property="Canvas.Top" Value="{Binding Y}"/>
                </Style>
            </ItemsControl.ItemContainerStyle>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Border BorderBrush="Red" BorderThickness="1" Width="{Binding Width}" Height="{Binding Height}"/>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </Grid>
  • 相关阅读:
    Pandas 数值计算和统计基础
    Pandas 基本技巧
    Pandas 索引和切片
    Pandas 数据结构Dataframe:基本概念及创建
    Pandas 数据结构Series:基本概念及创建
    Numpy 通用函数
    Numpy 随机数
    Numpy 索引及切片
    Numpy 练习题
    Python通过fork的方式防止僵尸进程
  • 原文地址:https://www.cnblogs.com/bruce1992/p/15303466.html
Copyright © 2011-2022 走看看