如何绘制圆圈并在c＃中移动

Question

I'm trying to draw one circle and move it in one form in c #. I use GDI to draw, as follows. Suppose that I have 1 class Circle

int postitionX, postitionY, radius, angle;
void Draw(Graphics g)
{
    g.DrawEllipse(Pen, postitionX, postitionY, radius, radius);
    g.FillEllipse(SolidBrush, postitionX, postitionY, radius, radius);
}

and in form main I init circle(postitionX=0, postitionY=10, radius=20, angle=30;)

private void form_Paint(object sender, PaintEventArgs e)
{
     <caculation postition next>
    mycircle.Draw(e.Graphics)
}

But the problem is that function form_Paint run many times and make circle move out display. Can someone give me no solution?

Answer 1

Invalidate will cause a full repaint of your form and will invoke your `form_Paint' event handler. This will cause an endless loop. (I see now TaW was just earlier). If you want to animate a circle on your form, you could use the following approach:

Put a Timer on your form, set Interval on 30 and Enabled to True. Implement the Tick event:

private int deltaX = 1;

private int deltaY = 1;

private void timer1_Tick(object sender, EventArgs e)
{ 
    // TO DO your caculation postition, like so:
    // be sure window width/height  is much larger than 2 * radius:           
    if ((postitionX - radius) <= 0)
        deltaX = 1;
    if ((postitionX + radius) >= ClientRectangle.Width)
        deltaX = -1;
    positionX += deltaX;

    if ((postitionY - radius) <= 0)
        deltaY = 1;
    if ((postitionY + radius) >= ClientRectangle.Heigth)
        deltaY = -1;
    positionY += deltaY;
    // Now you have calculated a 'new animation frame'. 

    // Now force repaint to draw.
    Invalidate(); // This will force a repaint
}

Now update your form_Paint handler:

private void form_Paint(object sender, PaintEventArgs e)
{
    // caculation postition next HAS TO BE REMOVED FROM HERE
    mycircle.Draw(e.Graphics)
    // Invalidate(); HAS TO BE REMOVED FROM HERE
}

By playing with the valye for timer1.Interval in combination with your calculations of next position, you can make the animation slower or faster.

Answer 2

So suppose I draw the path of the circle go to 3 points. if i use timer tick then how.

private void timer1_Tick(object sender, EventArgs e)
{
// Go to point 1  
// Go to point 2 
// Go to point 3
}
private void form_Paint(object sender, PaintEventArgs e)
{
    // caculation postition next HAS TO BE REMOVED FROM HERE
    mycircle.Draw(e.Graphics)
    // Invalidate(); HAS TO BE REMOVED FROM HERE
}

So the circle will go through point 3 then form_main start redraw.I did not want that. So, how can not you