C#在Canvas中拖放图像 [英] C# Drag and Drop Image within Canvas
问题描述
我尝试过谷歌如何拖拉在Canvas上为UIElements添加,但找不到任何我想要的东西。
I tried to Google how to make drag & drop for UIElements on a Canvas, but couldn't find anything that I'm looking for.
我有一个带有Window的C#WPF应用程序。在窗口内,我有一个画布,我可以添加图像。
我想要的是能够拖放拖放图像,同时留在画布边框内。
我也希望这是在代码中,所以不要在xaml。
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.
我在这个功能里添加/更新图片到画布。 TODO应该被替换为Drag&删除事件
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.
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:虽然这是为了以后,如果有人有代码一次拖放多个图像,额外的奖金,我会很感激。
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.
提前感谢帮助。
推荐答案
使用以下代码修复了我的问题:
Fixed my problem below, by using the following code:
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:
-
修正了当我将鼠标拖动到快速位置时,鼠标滑过图像的一个小错误。这种情况经常发生,即使我甚至没有将拖动图像移动到这个快速的位置。 - 使其能够一次性拖放多个图像通过选择多个第一,然后拖放它们,同时留在画布内。
将创建一个新的这个问题。
Will make a new Question for this.
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