c# - 如何在WPF中实现 "infinite-sized" Canvas 效果？

Question

我的目标是创建一个 Canvas ，您只需在整个 Canvas 上移动即可将子元素转换到您想要的位置(例如在 rhino 的 grasshopper 插件中)。我尝试使用“translateTransform”，但问题出现了， Canvas 的高度或宽度不够大，无法再次包含整个窗口。我试图通过在 Canvas 被拖动时添加 Width 和 Height 来解决这个问题，但 Canvas 的大小似乎没有改变。

这是我的 window.xaml:

<Window x:Name="Window" x:Class="Oolong.Windows.Project.ProjectPlan"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Oolong.Windows.Project"
        mc:Ignorable="d"
        Title="Projektplan" Height="{DynamicResource {x:Static SystemParameters.PrimaryScreenHeightKey}}" Width="{DynamicResource {x:Static SystemParameters.PrimaryScreenWidthKey}}" WindowStartupLocation="CenterOwner" ShowInTaskbar="False" Icon="/Oolong;component/Resources/Images/icon2.png">
    <Window.Background>
        <ImageBrush ImageSource="/Oolong;component/Resources/Images/ui/canvas_bg.png" TileMode="FlipY"      Stretch="Uniform" AlignmentY="Top"  Viewport="0,0,150,50" ViewportUnits="Absolute" />
    </Window.Background>
    <Canvas x:Name="Grid" ScrollViewer.HorizontalScrollBarVisibility="Auto" ScrollViewer.VerticalScrollBarVisibility="Auto" MouseLeftButtonDown="Grid_OnMouseLeftButtonDown" MouseDown="Grid_MouseDown" MouseMove="Grid_MouseMove" MouseUp="Grid_MouseUp" MouseWheel="Grid_OnMouseWheel" Width="{DynamicResource {x:Static SystemParameters.MaximizedPrimaryScreenWidthKey}}" Height="{DynamicResource {x:Static SystemParameters.MaximizedPrimaryScreenHeightKey}}">
        <Rectangle x:Name="NewTaskRectangle" Fill="#FFF4F4F5" HorizontalAlignment="Left" Height="87" Margin="0,0,0,0" Stroke="Black" VerticalAlignment="Top" Width="208" Visibility="Hidden"/>
            <Label x:Name="NewTaskLabel" Content="Gib den Namen der Aufgabe ein..." HorizontalAlignment="Left" Margin="10,17,0,0" VerticalAlignment="Top" Visibility="Hidden"/>
            <TextBox  x:Name="NewTaskTextBox" HorizontalAlignment="Left" Height="23" Margin="10,48,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="189" Visibility="Hidden" KeyUp="NewTaskTextBox_OnKeyUp"/>
            <Border x:Name="NewTaskTemplate" BorderBrush="Black" BorderThickness="2.5" HorizontalAlignment="Left" Height="30" Margin="0" VerticalAlignment="Top" Background="#FFE2C027" Padding="5" Focusable="True" CornerRadius="6" Width="15" Visibility="Hidden" MinWidth="150" MinHeight="30" MouseRightButtonUp="NewTaskTemplate_OnMouseRightButtonUp">
                <Border.ContextMenu>
                    <ContextMenu x:Name="NewTaskContextMenu">
                        <MenuItem x:Name="AddIssueMenuItem" Header="Arbeitsschritt hinzufügen" Click="AddIssueMenuItem_OnClick"/>
                        <MenuItem x:Name="DeleteMenuItem" Header="Löschen" Click="DeleteMenuItem_OnClick"/>
                    </ContextMenu>
                </Border.ContextMenu>
            </Border>
        <Canvas.RenderTransform>
            <TransformGroup>
                <ScaleTransform x:Name="ScaleTransform"/>
                <TranslateTransform x:Name="Tt" />
            </TransformGroup>
        </Canvas.RenderTransform>
    </Canvas>
</Window>

这里是相关的 C# 代码:

 private void NewTaskTemplate_OnMouseRightButtonUp(object sender, MouseButtonEventArgs e)
    {
        Point position = e.GetPosition(Grid);
        bool hasClickedOnTask = false;
        if (App.ProjectPlan.Tasks != null)
        {
            var tasks = App.ProjectPlan.Tasks.DistinctBy(task => task.Position);
            var selectedTasks =
                tasks.Where(
                (task =>
                    Math.Abs(task.Position.X - position.X + 10) < task.Title.Length*13 &&
                    Math.Abs(task.Position.Y - position.Y) < 20));
            IEnumerable<Task> enumerable = selectedTasks as Task[] ?? selectedTasks.ToArray();
            if (enumerable.Any())
            {
                _selectedTask = enumerable.Last();
                hasClickedOnTask = true;
            }
        }
        if (!hasClickedOnTask) return;
        NewTaskContextMenu.IsOpen = true;
        e.Handled = true;
        SetGridSize();
    }

    Point _mStart;
    Vector _mStartOffset;

    private void SetGridSize()
    {
        Grid.Width += 250;
        Grid.Height += 250;
        Grid.UpdateLayout();
    }

    private void Grid_MouseDown(object sender, MouseButtonEventArgs e)
    {
        Grid.Cursor = Cursors.ScrollAll;
        _mStart = e.GetPosition(Window);
        _mStartOffset = new Vector(Tt.X, Tt.Y);
        Grid.CaptureMouse();
    }

    private void Grid_MouseMove(object sender, MouseEventArgs e)
    {
        if (Grid.IsMouseCaptured)
        {
            Vector offset = Point.Subtract(e.GetPosition(Window), _mStart);

            Tt.X = _mStartOffset.X + offset.X;
            Tt.Y = _mStartOffset.Y + offset.Y;
            SetGridSize();
        }
    }

    private void Grid_MouseUp(object sender, MouseButtonEventArgs e)
    {
        Grid.ReleaseMouseCapture();
        Grid.Cursor = Cursors.Arrow;
    }

    private void Grid_OnMouseWheel(object sender, MouseWheelEventArgs e)
    {
        Point position = e.GetPosition(Window);
        ScaleTransform.CenterX = position.X;
        ScaleTransform.CenterY = position.Y;
        _gridZoom = _gridZoom + e.Delta / 2400.00;
        ScaleTransform.ScaleX = _gridZoom;
        ScaleTransform.ScaleY = _gridZoom;
        if (e.Delta > 0)
        {
            SetGridSize();
        }
        e.Handled = true;
    }

Canvas 一开始是一个网格，但也不起作用。它可以在 Canvas 上移动，当然包括所有元素，但是如果你把它放在窗外，你就不能再移动任何东西了，因为 Canvas 已经不存在了。我该如何解决这个问题，让用户觉得 Canvas 是无限的？

Answer 1

在这种情况下，您应该使用 ScrollView 围绕您的 Grid 并在每次放置后编辑 Width 和 Height 属性`Grid' 之外的拖动元素。像这样:

private void UIElement_OnPreviewMouseMove(object sender, MouseEventArgs e)
    {
        if (canmove) //field is used to define whether element dragged or not
        {
            var c = (Control) sender;
            c.SetValue(Canvas.LeftProperty, e.GetPosition(Canvas).X - p.X);
            c.SetValue(Canvas.TopProperty, e.GetPosition(Canvas).Y - p.Y);

            var leftprop = Convert.ToDouble(c.GetValue(Canvas.LeftProperty));
            if (leftprop > Canvas.Width)
                Canvas.Width = leftprop + c.Width+10;
           
        }
    }