C# 在 WPF 中单击并拖动选择框

Click and drag selection box in WPF

提问by rem

Is it possible to implement mouse click and drag selection box in WPF. Should it be done through simply drawing a rectangle, calculating coordinates of its points and evaluating position of other objects inside this box? Or are there some other ways?

是否可以在 WPF 中实现鼠标单击和拖动选择框。是否应该通过简单地绘制一个矩形，计算其点的坐标并评估此框中其他对象的位置来完成？或者有其他一些方法吗？

Could you give a bit of sample code or a link?

你能给一些示例代码或链接吗？

采纳答案by Ashley Davis

Here is sample code for a simple technique that I have used in the past to draw a drag selection box.

这是我过去用来绘制拖动选择框的一种简单技术的示例代码。

XAML:

XAML：

<Window x:Class="DragSelectionBox.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300"
    >
    <Grid
        x:Name="theGrid"
        MouseDown="Grid_MouseDown"
        MouseUp="Grid_MouseUp"
        MouseMove="Grid_MouseMove"
        Background="Transparent"
        >
        <Canvas>
            <!-- This canvas contains elements that are to be selected -->
        </Canvas>

        <Canvas>
            <!-- This canvas is overlaid over the previous canvas and is used to 
                place the rectangle that implements the drag selection box. -->
            <Rectangle
                x:Name="selectionBox"
                Visibility="Collapsed"
                Stroke="Black"
                StrokeThickness="1"
                />
        </Canvas>
    </Grid>
</Window>

C#:

C＃：

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();
    }

    bool mouseDown = false; // Set to 'true' when mouse is held down.
    Point mouseDownPos; // The point where the mouse button was clicked down.

    private void Grid_MouseDown(object sender, MouseButtonEventArgs e)
    {
        // Capture and track the mouse.
        mouseDown = true;
        mouseDownPos = e.GetPosition(theGrid);
        theGrid.CaptureMouse();

        // Initial placement of the drag selection box.         
        Canvas.SetLeft(selectionBox, mouseDownPos.X);
        Canvas.SetTop(selectionBox, mouseDownPos.Y);
        selectionBox.Width = 0;
        selectionBox.Height = 0;

        // Make the drag selection box visible.
        selectionBox.Visibility = Visibility.Visible;
    }

    private void Grid_MouseUp(object sender, MouseButtonEventArgs e)
    {
        // Release the mouse capture and stop tracking it.
        mouseDown = false;
        theGrid.ReleaseMouseCapture();

        // Hide the drag selection box.
        selectionBox.Visibility = Visibility.Collapsed;

        Point mouseUpPos = e.GetPosition(theGrid);

        // TODO: 
        //
        // The mouse has been released, check to see if any of the items 
        // in the other canvas are contained within mouseDownPos and 
        // mouseUpPos, for any that are, select them!
        //
    }

    private void Grid_MouseMove(object sender, MouseEventArgs e)
    {
        if (mouseDown)
        {
            // When the mouse is held down, reposition the drag selection box.

            Point mousePos = e.GetPosition(theGrid);

            if (mouseDownPos.X < mousePos.X)
            {
                Canvas.SetLeft(selectionBox, mouseDownPos.X);
                selectionBox.Width = mousePos.X - mouseDownPos.X;
            }
            else
            {
                Canvas.SetLeft(selectionBox, mousePos.X);
                selectionBox.Width = mouseDownPos.X - mousePos.X;
            }

            if (mouseDownPos.Y < mousePos.Y)
            {
                Canvas.SetTop(selectionBox, mouseDownPos.Y);
                selectionBox.Height = mousePos.Y - mouseDownPos.Y;
            }
            else
            {
                Canvas.SetTop(selectionBox, mousePos.Y);
                selectionBox.Height = mouseDownPos.Y - mousePos.Y;
            }
        }
    }
}

回答by Josh

You can get this functionality pretty easily by adding an InkCanvas and set its EditingMode to Select. Although it's primarily intended for Tablet PC ink collection and rendering, it's very easy to use it as a basic designer surface.

您可以通过添加 InkCanvas 并将其 EditingMode 设置为 Select 来轻松获得此功能。尽管它主要用于 Tablet PC 墨水收集和渲染，但将其用作基本的设计器表面非常容易。

<Window Width="640" Height="480" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
    <InkCanvas EditingMode="Select">
        <Button Content="Button" Width="75" Height="25"/>
        <Button Content="Button" Width="75" Height="25"/>
    </InkCanvas>
</Window>

回答by user7128900

MouseDown logic:

鼠标按下逻辑：

MouseRect.X = mousePos.X >= MouseStart.X ? MouseStart.X : mousePos.X;
MouseRect.Y = mousePos.Y >= MouseStart.Y ? MouseStart.Y : mousePos.Y;
MouseRect.Width = Math.Abs(mousePos.X - MouseStart.X);
MouseRect.Height = Math.Abs(mousePos.Y - MouseStart.Y);