wpf C# 在画布中拖放图像
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C# Drag and Drop Image within Canvas
提问by Kevin Cruijssen
I tried to Google how to make drag & drop for UIElements on a Canvas, but couldn't find anything that I'm looking for.
我试图谷歌如何在画布上为 UIElements 进行拖放，但找不到我正在寻找的任何东西。
I got a C# WPF application with a Window. Inside the Window I got a Canvas where I can add Images to. What I want is to be able to Drag & Drop the Images, while staying within the Canvas' borders. I also want this to be in code, so not in the xaml.
我有一个带有 Window 的 C# WPF 应用程序。在窗口内，我有一个 Canvas，我可以在其中添加图像。我想要的是能够拖放图像，同时保持在画布的边界内。我也希望它在代码中，而不是在 xaml 中。
I got this in the function where I add/update the Images to the Canvas. The TODO's should be replaced for the Drag & Drop events.
我在将图像添加/更新到画布的函数中得到了这个。拖放事件的 TODO 应该被替换。
Image img = ImageList[i].Image;
img.Name = "Image" + i;
// TODO: Drag and Drop event for Image
// TODO: Check if Left and Top are within Canvas (minus width / height of Image)
Canvas.SetLeft(img, Left); // Default Left when adding the image = 0
Canvas.SetTop(img, Top); // Default Top when adding the image = 0
MyCanvas.Children.Add(img);
OnPropertyChanged("MyCanvas");
PS: Though this is for later, if someone has code to drag and drop multiple images at once as an additional bonus, I would appreciate it.
PS：虽然这是以后用的，但如果有人有代码可以一次拖放多个图像作为额外的奖励，我将不胜感激。
Thanks in advance for the help.
在此先感谢您的帮助。
采纳答案by Kevin Cruijssen
Fixed my problem below, by using the following code:
使用以下代码修复了我的问题：
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);
}
}
This code allows me to drag-and-drop the Images inside the Canvas, without leaving the Canvas itself.
此代码允许我将图像拖放到画布内，而无需离开画布本身。
Now I just need to be able to do two more things:
现在我只需要能够做两件事：
Fix a little bug where my Mouse slips of the Image when I drag them around to fast. This happens quite often, even when I'm not even moving the dragging image around THAT fast..Fixed by using the solution mentioned in my other question.- Making it able to drag-and-drop multiple images at once, preferably by selecting multiple first, and then drag-and-drop the whole bunch of them while staying inside the Canvas.
修复一个小错误，当我将它们快速拖动时，我的鼠标滑过图像。这种情况经常发生，即使我什至没有那么快地移动拖动图像......通过使用我的另一个问题中提到的解决方案修复。- 使其能够一次拖放多个图像，最好先选择多个图像，然后在留在画布内的同时拖放整组图像。
Will make a new Question for this.
将为此提出一个新问题。
回答by Temitayo
I was did a project that uses a chunk of your code and does drag and drop on canvas, look into it and see if there be any difference, dont really have the time to check
我做了一个项目，它使用了你的一大块代码，并在画布上拖放，查看它是否有任何区别，真的没有时间检查
private void pinCanvas_PreviewMouseLeftButtonDown_1(object sender, MouseButtonEventArgs e)
{
// Point pt = e.GetPosition(pinCanvas);
// Curosor.Text = String.Format("You are at ({0}in, {1}in) in window coordinates", (pt.X / (96 / 72)) * 1/72, (pt.Y / (96 / 72)) * 1/72);
}
bool captured = false;
double x_shape, x_canvas, y_shape, y_canvas;
UIElement source = null;
string elementName;
double elementHeight, elementWidth;
private void pinCanvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
setCanvasSize();
source = (UIElement)sender;
elementName = ((Label)source).Name;
switch (elementName)
{
case "pinTextBox" :
elementHeight = pinActualHeight;
elementWidth = pinActualWidth;
break;
case "serialTextBox" :
elementHeight = serialActualHeight;
elementWidth = serialActualWidth;
break;
case "batchTextBox" :
elementHeight = batchActualHeight;
elementWidth = batchActualWidth;
break;
}
Mouse.Capture(source);
captured = true;
x_shape = Canvas.GetLeft(source);
x_canvas = e.GetPosition(Maincanvas).X;
y_shape = Canvas.GetTop(source);
y_canvas = e.GetPosition(Maincanvas).Y;
}
private void pinCanvas_MouseMove(object sender, MouseEventArgs e)
{
if (captured)
{
double x = e.GetPosition(Maincanvas).X;
double y = e.GetPosition(Maincanvas).Y;
var xCond = Math.Round(appActivities.DIP2Inch(x_shape), 4).ToString();
var yCond = Math.Round(appActivities.DIP2Inch(y_shape), 4).ToString();
var name = ((Label)source).Name;
x_shape += x - x_canvas;
// if ((x_shape < Maincanvas.ActualWidth - elementWidth) && x_shape > 0)
// {
Canvas.SetLeft(source, x_shape);
switch (name)
{
case "pinTextBox" :
pinOffsetLeft.Text = xCond;
break;
case "serialTextBox" :
serialOffsetLeft.Text = xCond;
break;
case "batchTextBox" :
batchOffsetLeft.Text = xCond;
break;
}
// }
x_canvas = x;
y_shape += y - y_canvas;
// if (y_shape < Maincanvas.ActualHeight - elementHeight && y_shape > 0)
// {
Canvas.SetTop(source, y_shape);
switch (name)
{
case "pinTextBox":
pinOffsetTop.Text = yCond;
break;
case "serialTextBox":
serialOffsetTop.Text = yCond;
break;
case "batchTextBox":
batchOffsetTop.Text = yCond;
break;
}
// }
y_canvas = y;
}
}
private void pinCanvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
Mouse.Capture(null);
captured = false;
// MessageBox.Show((Canvas.GetTop(source)).ToString());
/* if (Canvas.GetTop(source) < 0)
{
Canvas.SetTop(source, 0);
}
if (Canvas.GetLeft(source) < 0)
{
Canvas.SetLeft(source, 0);
}
if (Canvas.GetLeft(source) > Maincanvas.ActualWidth - elementWidth)
{
// MessageBox.Show("Left Too Much " + (Canvas.GetLeft(source) * 1/96).ToString());
Canvas.SetLeft(source, Maincanvas.ActualWidth - elementWidth);
}
if (Canvas.GetTop(source) > Maincanvas.ActualHeight - elementHeight)
{
Canvas.SetTop(source, Maincanvas.ActualHeight - elementHeight);
} */
oneElemntTorched = true;
//MessageBox.Show(this.pinTextBox.ActualHeight.ToString() + ", " + this.pinTextBox.ActualWidth.ToString());
}
