如何删除一个帆布的一个孩子后，我加入了吗？ [英] How to remove a single child of a single canvas after I added it?

问题描述

我有一个WPF项目中，我要创建一个画布上几个省略号。我创建了两个复选框，当我在第一个复选框选中，红色的椭圆会显示在画布上。如果我取消选中第一个复选框，椭圆将会消失....第二个复选框将创建一个蓝色的椭圆形，而不是具有相同的功能。

因此，继承人我的情况，当两个复选框被选中，蓝色和红色的椭圆会出现。要清除画布上的椭圆形，我用的是 myCanvas.children.clear（）。但是，当我取消选中该复选框中的一个，两个椭圆的将被删除。

 私人无效redCB_Checked（对象发件人，RoutedEventArgs E）
 {
 drawRedCircle（）; 
} 
 
私人无效redCB_Unchecked（对象发件人，RoutedEventArgs E）
 {
 myCanvas.Children.Clear（）; 
} 
 
私人无效blueCB_Checked（对象发件人，RoutedEventArgs E）
 {
 drawBlueCircle（）; 
} 
 
私人无效blueCB_Unchecked（对象发件人，RoutedEventArgs E）
 {
 myCanvas.Children.Clear（）; 
} 
 
私人无效drawRedCircle（）
 {
椭圆myCircle =新的椭圆（）; 
 myCircle.Stroke = Brushes.Red; 
 myCircle.Width = 30; 
 myCircle.Height = 30; 
 myCircle.StrokeThickness = 2; 
 
 Canvas.SetLeft（myCircle，10）; 
 Canvas.SetRight（myCircle，10）; 
 Canvas.SetBottom（myCircle，10）; 
 Canvas.SetTop（myCircle，10）; 
 
 myCanvas.Children.Add（myCircle）; 
} 
 
私人无效drawBlueCircle（）
 {
椭圆myCircle =新的椭圆（）; 
 myCircle.Stroke = Brushes.Blue; 
 myCircle.Width = 30; 
 myCircle.Height = 30; 
 myCircle.StrokeThickness = 2; 
 
 Canvas.SetLeft（myCircle，20）; 
 Canvas.SetRight（myCircle，20）; 
 Canvas.SetBottom（myCircle，20）; 
 Canvas.SetTop（myCircle，20）; 
 
 myCanvas.Children.Add（myCircle）; 
} 
  

解决方案

如果你给的加圈一个名字，你可以找到它时，复选框被选中，然后很容易地将其删除。

 私人字符串redCircleName =redCircle ; 
私人字符串blueCircleName =blueCircle; 
 
私人无效redCB_Checked（对象发件人，RoutedEventArgs E）
 {
 drawRedCircle（）; 
} 
 
私人无效redCB_Unchecked（对象发件人，RoutedEventArgs E）
 {
 RemoveCircleByName（redCircleName）; 
} 
 
私人无效blueCB_Checked（对象发件人，RoutedEventArgs E）
 {
 drawBlueCircle（）; 
} 
 
私人无效blueCB_Unchecked（对象发件人，RoutedEventArgs E）
 {
 RemoveCircleByName（blueCircleName）; 
} 
 
私人无效RemoveCircleByName（字符串名称）
 {
 VAR圈=（的UIElement）LogicalTreeHelper.FindLogicalNode（myCanvas，名）; 
 myCanvas.Children.Remove（圈）; 
} 
 
私人无效drawRedCircle（）
 {
椭圆myCircle =新的椭圆（）; 
 myCircle.Stroke = Brushes.Red; 
 myCircle.Width = 30; 
 myCircle.Height = 30; 
 myCircle.StrokeThickness = 2; 
 
 //给它一个名字在这里，所以我们以后可以
 myCircle.Name = redCircleName找到它; 
 
 Canvas.SetLeft（myCircle，10）; 
 Canvas.SetRight（myCircle，10）; 
 Canvas.SetBottom（myCircle，10）; 
 Canvas.SetTop（myCircle，10）; 
 
 myCanvas.Children.Add（myCircle）; 
} 
 
私人无效drawBlueCircle（）
 {
椭圆myCircle =新的椭圆（）; 
 myCircle.Stroke = Brushes.Blue; 
 myCircle.Width = 30; 
 myCircle.Height = 30; 
 myCircle.StrokeThickness = 2; 
 
 //给它一个名字在这里，所以我们以后可以
 myCircle.Name = blueCircleName找到它; 
 
 Canvas.SetLeft（myCircle，20）; 
 Canvas.SetRight（myCircle，20）; 
 Canvas.SetBottom（myCircle，20）; 
 Canvas.SetTop（myCircle，20）; 
 
 myCanvas.Children.Add（myCircle）; 
} 
  

I have a WPF project where i have to create a few ellipses on a canvas. I create two check Box and when i check on the first checkbox, the red ellipse will show on the canvas. If i uncheck the first check box, the ellipse will be disappear....the second check box will have the same function by creating a blue ellipse instead.

So heres my situation, when the two checkboxes are checked, a blue and a red ellipse will appear. To clear the ellipse on the canvas, i use the myCanvas.children.clear(). But when i uncheck one of the checkbox, both of the ellipse will be deleted.

private void redCB_Checked(object sender, RoutedEventArgs e)
    {
       drawRedCircle();
    }

private void redCB_Unchecked(object sender, RoutedEventArgs e)
    {
       myCanvas.Children.Clear();
    }

private void blueCB_Checked(object sender, RoutedEventArgs e)
    {
       drawBlueCircle();
    }

private void blueCB_Unchecked(object sender, RoutedEventArgs e)
    {
       myCanvas.Children.Clear();
    }

private void drawRedCircle()
    {
        Ellipse myCircle = new Ellipse();
        myCircle.Stroke = Brushes.Red;
        myCircle.Width = 30;
        myCircle.Height = 30;
        myCircle.StrokeThickness = 2;

        Canvas.SetLeft(myCircle, 10);
        Canvas.SetRight(myCircle, 10);
        Canvas.SetBottom(myCircle, 10);
        Canvas.SetTop(myCircle, 10);

        myCanvas.Children.Add(myCircle);
    }

 private void drawBlueCircle()
    {
        Ellipse myCircle = new Ellipse();
        myCircle.Stroke = Brushes.Blue;
        myCircle.Width = 30;
        myCircle.Height = 30;
        myCircle.StrokeThickness = 2;

        Canvas.SetLeft(myCircle, 20);
        Canvas.SetRight(myCircle, 20);
        Canvas.SetBottom(myCircle, 20);
        Canvas.SetTop(myCircle, 20);

        myCanvas.Children.Add(myCircle);
    }

解决方案

If you give the added circle a name, you can find it when the checkbox is unchecked and then remove it pretty easily.

private string redCircleName = "redCircle";
private string blueCircleName = "blueCircle";

private void redCB_Checked(object sender, RoutedEventArgs e)
{
    drawRedCircle();
}

private void redCB_Unchecked(object sender, RoutedEventArgs e)
{
    RemoveCircleByName(redCircleName);
}

private void blueCB_Checked(object sender, RoutedEventArgs e)
{
    drawBlueCircle();
}

private void blueCB_Unchecked(object sender, RoutedEventArgs e)
{
    RemoveCircleByName(blueCircleName);
}

private void RemoveCircleByName(string name)
{
    var circle = (UIElement)LogicalTreeHelper.FindLogicalNode(myCanvas, name);
    myCanvas.Children.Remove(circle);
}

private void drawRedCircle()
{
    Ellipse myCircle = new Ellipse();
    myCircle.Stroke = Brushes.Red;
    myCircle.Width = 30;
    myCircle.Height = 30;
    myCircle.StrokeThickness = 2;

    //Give it a name here so we can find it later
    myCircle.Name = redCircleName;

    Canvas.SetLeft(myCircle, 10);
    Canvas.SetRight(myCircle, 10);
    Canvas.SetBottom(myCircle, 10);
    Canvas.SetTop(myCircle, 10);

    myCanvas.Children.Add(myCircle);
}

private void drawBlueCircle()
{
    Ellipse myCircle = new Ellipse();
    myCircle.Stroke = Brushes.Blue;
    myCircle.Width = 30;
    myCircle.Height = 30;
    myCircle.StrokeThickness = 2;

    //Give it a name here so we can find it later
    myCircle.Name = blueCircleName;

    Canvas.SetLeft(myCircle, 20);
    Canvas.SetRight(myCircle, 20);
    Canvas.SetBottom(myCircle, 20);
    Canvas.SetTop(myCircle, 20);

    myCanvas.Children.Add(myCircle);
}

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