C＃拖&在画布中放置多个图像 [英] C# Drag & Drop Multiple Images within Canvas

问题描述

我有以下代码可以在Canvas内拖放图像：

I've got the following code to drag and drop images inside my Canvas:

img.AllowDrop = true;
img.PreviewMouseLeftButtonDown += this.MouseLeftButtonDown;
img.PreviewMouseMove += this.MouseMove;
img.PreviewMouseLeftButtonUp += this.PreviewMouseLeftButtonUp;


private object movingObject;
private double firstXPos, firstYPos;
private void MouseLeftButtonDown(object sender, MouseButtonEventArgs e) {
    // In this event, we get the current mouse position on the control to use it in the MouseMove event.
    Image img = sender as Image;
    Canvas canvas = img.Parent as Canvas;

    firstXPos = e.GetPosition(img).X;
    firstYPos = e.GetPosition(img).Y;

    movingObject = sender;

    // Put the image currently being dragged on top of the others
    int top = Canvas.GetZIndex(img);
    foreach (Image child in canvas.Children)
        if (top < Canvas.GetZIndex(child))
            top = Canvas.GetZIndex(child);
    Canvas.SetZIndex(img, top + 1);
}
private void PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e) {
    Image img = sender as Image;
    Canvas canvas = img.Parent as Canvas;

    movingObject = null;

    // Put the image currently being dragged on top of the others
    int top = Canvas.GetZIndex(img);
    foreach (Image child in canvas.Children)
        if (top > Canvas.GetZIndex(child))
            top = Canvas.GetZIndex(child);
    Canvas.SetZIndex(img, top + 1);
}
private void MouseMove(object sender, MouseEventArgs e) {
    if (e.LeftButton == MouseButtonState.Pressed && sender == movingObject) {
        Image img = sender as Image;
        Canvas canvas = img.Parent as Canvas;

        double newLeft = e.GetPosition(canvas).X - firstXPos - canvas.Margin.Left;
        // newLeft inside canvas right-border?
        if (newLeft > canvas.Margin.Left + canvas.ActualWidth - img.ActualWidth)
            newLeft = canvas.Margin.Left + canvas.ActualWidth - img.ActualWidth;
        // newLeft inside canvas left-border?
        else if (newLeft < canvas.Margin.Left)
            newLeft = canvas.Margin.Left;
        img.SetValue(Canvas.LeftProperty, newLeft);

        double newTop = e.GetPosition(canvas).Y - firstYPos - canvas.Margin.Top;
        // newTop inside canvas bottom-border?
        if (newTop > canvas.Margin.Top + canvas.ActualHeight - img.ActualHeight)
            newTop = canvas.Margin.Top + canvas.ActualHeight - img.ActualHeight;
        // newTop inside canvas top-border?
        else if (newTop < canvas.Margin.Top)
            newTop = canvas.Margin.Top;
        img.SetValue(Canvas.TopProperty, newTop);
    }
}

此代码允许我拖放画布中的图片，而不会离开画布本身。

This code allows me to drag-and-drop the Images inside the Canvas, without leaving the Canvas itself.

现在我只需要再做两件事：

Now I just need to be able to do two more things:

1. 当我将鼠标拖动到快速位置时，修复了鼠标滑动图像的一个小错误。这种情况经常发生，即使我甚至不能快速移动拖动图像。


2. 使其能够一次拖放多个图像，最好选择多个首先，然后将它们拖放到Canvas内。

PS：我以前的问题可以是发现此处。

PS: My previously question can be found here.

推荐答案

你需要将鼠标锁定到图像上，以停止光标滑出MouseCapture（imageReference）你可以使用Mouse.Capture（null）鼠标放开它 - Andy Feb 18 at 15:58

You'll want to lock the mouse on to the image to stop the cursor slipping off it Mouse.Capture (imageReference), you can release it on mouse up with Mouse.Capture (null) – Andy Feb 18 at 15:58

使用Andy的建议之后，添加：

After using Andy's suggestion, by adding:

Mouse.Capture(img);

位于MouseLeftButtonDown功能的底部，

at the bottom of the MouseLeftButtonDown-function, and

Mouse.Capture(null);

在PreviewMouseLeftButtonUp函数的底部，它的作用就像一个魅力。 所以非常感谢Andy！

at the bottom of the PreviewMouseLeftButtonUp-function, it works like a charm. So thanks a lot Andy!

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