将Windows窗体颜色从一种更改为另一种

Question

I'm currently following the Head First C# but every so often I play around on my own. I ran into a situation that I'm unable to solve. I want to change this.BackColor from MediumBlue to step through green 0 - 255 and back to console with a button I/O. The issue is that I can't get the color to stop stepping and go back to MediumBlue.

private void btnClr_Click(object sender, EventArgs e)
    {
        int fClr = 0;
        while (Visible)
        {
            if (fClr == 0)
            {
                fClr++;
                for (int nBackClr = 0; nBackClr < 255 && Visible; nBackClr++)
                {
                    this.BackColor = Color.FromArgb(nBackClr, 255 - nBackClr, nBackClr);
                    Application.DoEvents();
                    Thread.Sleep(2);
                }
                for (int z = 255; z >= 0 && Visible; z--)
                {
                    this.BackColor = Color.FromArgb(z, 255 - z, z);
                    Application.DoEvents();
                    Thread.Sleep(2);
                }
            }
            else
            {
                fClr--;
                this.BackColor = Color.MediumBlue;
                Application.DoEvents();
                Thread.Sleep(1);
            }
        }
    } 

Another thing I'd love to know is how to get the BackColor to go through the ENTIRE color palette.

EDIT: S/n After applying JABFreeware's solution. I added a breakpoint to see what was going on and fClr gets the value of 1 when I first click btnClr_Click . However when I click it again fClr gets 0 but then immediately gets 1 again. Not sure if this has to do with the while (Visible) . ..Head Scratcher..

Answer 1

One of your problems is that int fClr = 0; is inside the button click event handler so every time they click the button, its reset to 0. Move the variable outside the click event.

Like this:

        int fClr = 0;
private void btnClr_Click(object sender, EventArgs e)
    {
        while (Visible)
        {
            if (fClr == 0)
            {
                fClr++;
                for (int nBackClr = 0; nBackClr < 255 && Visible; nBackClr++)
                {
                    this.BackColor = Color.FromArgb(nBackClr, 255 - nBackClr, nBackClr);
                    Application.DoEvents();
                    Thread.Sleep(2);
                }
                for (int z = 255; z >= 0 && Visible; z--)
                {
                    this.BackColor = Color.FromArgb(z, 255 - z, z);
                    Application.DoEvents();
                    Thread.Sleep(2);
                }
            }
            else
            {
                fClr--;
                this.BackColor = Color.MediumBlue;
                Application.DoEvents();
                Thread.Sleep(1);
            }
        }
    }

Answer 2

It is easier to use a timer. That way your UI will remain responsive without using DoEvents .

const int ColorStep = 16;

private Timer _timer;
private int _r, _g, _b;

public frmRotateColors()
{
    InitializeComponent();
}

private void btnStart_Click(object sender, EventArgs e)
{
    _r = 0;
    _g = 0;
    _b = 0;

    // Start the timer
    _timer = new Timer { Interval = 10 };
    _timer.Tick += Timer_Tick;
    _timer.Start();
}

private void Timer_Tick(object sender, EventArgs e)
{
    if (_b >= 256) { 
        _timer.Dispose(); // Stop the timer.
        this.BackColor = SystemColors.Control; // Reset the background color.
    } else {
        this.BackColor = Color.FromArgb(_r, _g, _b);

        // Get next color
        _r += ColorStep;
        if (_r >= 256) {
            _r = 0;
            _g += ColorStep;
            if (_g >= 256) {
                _g = 0;
                _b += ColorStep;
            }
        }
    }
}

Here I rotate through all the colors by increasing the red color. If I am out of range of red colors (0 - 255) I reset the red color and increase the green color. If the green color range is exceeded I reset the green color and increase the blue color. Finally, if the blue color range is exceeded I terminate the process.