在 WinForms C# 中绘制实心圆

Question

I have a WinForms application that interacts with a connection. If the connection is fine I want to show a green ("everything is fine") filled circle, if not I want to show a red filled circle.

I found no circle element in the toolbox so I think I have to draw it on my own.

I created a picture box called picBoxClientState and started with this code

public partial class FrmMain : Form
{
    public void CheckSignedInState()
    {
        // some other code

        DrawClientStateIcon(client.IsSignedIn);
    }

    private void DrawClientStateIcon(bool isSignedIn)
    {
        Point rectangleLocation = picBoxClientState.Location;
        Size rectangleSize = picBoxClientState.Size;
        Rectangle rectangle = new Rectangle(rectangleLocation, rectangleSize);

        Color iconColor = isSignedIn ? Color.Green : Color.Red;
        SolidBrush iconBrush = new SolidBrush(iconColor);

        Graphics graphics = picBoxClientState.CreateGraphics();
        graphics.FillEllipse(iconBrush, rectangle);
    }
}

How can I draw on this picturebox whenever I call CheckSignedInState() ?

Maybe there is a better way instead of drawing? (I don't want to toggle two images because there might be more states to draw)

Answer 1

A simple example using a Label control to draw an ellipse.
You can use any control that has a Paint event to draw shapes.
It could also be a Panel , a PictureBox , a Button ...

A bool variable ( clientIsSignedIn ) declared at Class scope is used to keep track of the current status, as reported by your client.IsSignedIn value.

When the status changes, update clientIsSignedIn and Invalidate() the Control that provides the visual aid.

bool clientIsSignedIn = false;

public void CheckSignedInState()
{
    // some other code
    clientIsSignedIn = client.IsSignedIn;
    lblVisualStatus.Invalidate();
}

private void lblVisualStatus_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
    e.Graphics.FillEllipse((clientIsSignedIn) ? Brushes.Green : Brushes.Red, ((Control)sender).ClientRectangle);
}

Answer 2

I don't think picture box is necessary. You can try something like this:

private void button1_Click(object sender, EventArgs e)
{
    System.Drawing.SolidBrush myBrush = new 
    System.Drawing.SolidBrush(System.Drawing.Color.Red);
    System.Drawing.Graphics formGraphics;
    formGraphics = this.CreateGraphics();
    formGraphics.FillEllipse(myBrush, new Rectangle(200, 200, 30, 30));
    myBrush.Dispose();
    formGraphics.Dispose();
}

If you need to draw on picturebox be sure to call picturebox.Invalidate();

Answer 3

your code works, it did seem to draw a bit off center though but also the fact that you weren't disposing of the object could potentially cause issues too. Try using the code below as your DrawClientStateIcon method

Edit : full code example below. I added a button to toggle the state of the client and this works for me.

using System;
using System.Drawing;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public class Client
        {
            public bool IsSignedIn { get; set; }
        }

        Client client = new Client()
        {
            IsSignedIn = false
        };

        public Form1()
        {
            InitializeComponent();
        }

        public void CheckSignedInState()
        {
            // some other code

            DrawClientStateIcon(client.IsSignedIn);
        }

        private void DrawClientStateIcon(bool isSignedIn)
        {
            Point rectangleLocation = picBoxClientState.Location;
            Size rectangleSize = picBoxClientState.Size;
            Rectangle rectangle = new Rectangle(rectangleLocation, new Size(rectangleSize.Width / 2, rectangleSize.Height / 2));

            Color iconColor = isSignedIn ? Color.Green : Color.Red;

            using (SolidBrush iconBrush = new SolidBrush(iconColor))
            {
                using (Graphics graphics = picBoxClientState.CreateGraphics())
                {
                    graphics.FillEllipse(iconBrush, rectangle);
                }
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            client.IsSignedIn = !client.IsSignedIn;
            CheckSignedInState();
        }
    }
}

Answer 4

You need to call it in Form Shown event.

        private void FrmGraphics_Shown(object sender, EventArgs e)
        {
            DrawClientStateIcon(true);
        }
        private void DrawClientStateIcon(bool isSignedIn)
        {
            Point rectangleLocation = picBoxClientState.Location;
            Size rectangleSize = picBoxClientState.Size;
            Rectangle rectangle = new Rectangle(rectangleLocation, rectangleSize);

            Color iconColor = isSignedIn ? Color.Green : Color.Red;
            SolidBrush iconBrush = new SolidBrush(iconColor);

            Graphics graphics = base.CreateGraphics();
            graphics.FillEllipse(iconBrush, rectangle);
        }