C# how to change color of bouncing ball?

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I need to change color of ball When the ball collides on the edges of the form,From each collision its color should become random,and this color should be maintained until the second clash has occurred.
Anyone can help me please?

What I have tried:

public partial class Form2 : Form
    {
        Ball ball;
        Graphics g;
        public Form2()
        {
            InitializeComponent();
            g = this.CreateGraphics();
            ball = new Ball(80, 80, 30,30, g, this);

        }

        private void Form2_Paint(object sender, PaintEventArgs e)
        {
            ball.draw();
        }
    }



class Ball
    {
        public int x;
        public int y;
        public int r;
        public int s;
        public Graphics g;
        public Thread td;
        public Form2 fr;
        public SolidBrush myvariable;
        public Random rnd;
        public Ball(int x, int y, int r,int s, Graphics g, Form2 fr)
        {
            this.fr = fr;
            this.x = x;
            this.y = y;
            this.r = r;
            this.s = s;
            this.g = g;
            td = new Thread(run);
            td.Start();
        }
        public void draw()
        {
             myvariable = new SolidBrush(Color.FromArgb(rnd.Next(150), rnd.Next(205), rnd.Next(160)));
            g.FillEllipse(myvariable, x, y, r, s);
            
        }
        
        public void run()
        {
            for (;;)
            {
                this.move();
                Thread.Sleep(50);
            }
        }
        public void move()
        {
            int newball_x = x + r;
            int newball_y = y + s;
            if (newball_x < -5 || newball_x > this.fr.ClientSize.Width)
            {
                r = -r;
                
            }
            if (newball_y < 0 || newball_y > this.fr.ClientSize.Height)
            {
                s = -s;
            }
            x += r;
            y += s;
            this.fr.Invalidate();
        }
    }

Posted 8-Mar-18 3:15am

Suren97

Updated 9-Mar-18 2:10am

v5

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Comments

F-ES Sitecore 8-Mar-18 9:21am

You're persisting the balls coordinates already so persist its colour the same way. For generating random colours google "c# generate random colour"

Suren97 8-Mar-18 9:26am

i'm not imagine how can i do it?

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OriginalGriff · Answer 1 · 2018-03-08T05:43:00

Solution 1

Move the SolidBrush definition outside any method, so it becomes part of the class (you should do this anyway, as all Graphics objects are scarce resources and need to be Disposed correctly when you are finished with them - if you don't you will get problems as they run out).
The class then persists the value for you.
When you detect it hit the wall, Dispose the existing instance, and create a new SolidBrush using a random colour: How to choose a random color from System.Drawing.Color?[^]

Posted 8-Mar-18 5:43am

OriginalGriff

Comments

Suren97 8-Mar-18 12:06pm

Sorry, but i nothing understand

OriginalGriff 8-Mar-18 12:14pm

What part do you not understand? I'll try and explain that in a bit more detail...

Suren97 8-Mar-18 12:28pm

can't i write it without class?

Suren97 8-Mar-18 13:16pm

Well, i updated my code, now can you help me where should i write random color?

OriginalGriff 8-Mar-18 14:03pm

Nowhere in that.
Once again, you are just guessing aren't you? Your previous version was better...

When I said "Move the SolidBrush definition outside any method, so it becomes part of the class" I Meant just that: move it outside your Paint method so it becomes part of the class that contains the method. A Form is a class. That's why your code says
public partial class Form2 : Form
*Everything* in C# is in a class. There are no global variables or methods, they are all part of one class or another.

I know I've told you this before - yesterday I think - but you must stop just guessing and leaping into code. A few minutes of thinking and planning, working out what you need to do and designing something that covers what you want will make your life a whole load easier. And the whole job a load quicker to boot.

So throw that away, go back to the previous version and start planning instead of just typing and hoping it all sorts itself out!

Ralf Meier 9-Mar-18 3:14am

@OG:
He hasn't defined a SolidBrush, he has directly assigned a fixed brush to the 'FillElipse' - so he didn't understand what you mean ...

OriginalGriff 9-Mar-18 3:28am

He did in the first version...

Ralf Meier 9-Mar-18 3:19am

@Suren:
What OG means is :
You wrote in your code : g.FillEllipse(Brushes.DarkViolet, x, y, r, s);
Instead of using a fixed assignment you could also create a Variable of type Solidbrush with the startvalue Brushes.DarkViolet. This Variable must be declared outside the method 'draw'. Inside the method 'draw' you use this Variable instead of 'Brushes.DarkViolet'.
So now, if you wish (or like) you can change the assignment to this Variable (perhaps to 'Brushes.Blue') and the next time the draw-method is called the Ellipse is drawn in that color.
Did you now understand what is meant ...?

Suren97 9-Mar-18 3:33am

i don't know how can i declare random color?

OriginalGriff 9-Mar-18 3:35am

Follow the link in the original solution - it shows several methods...

Maciej Los 9-Mar-18 4:54am

Even with Ralf's explanation? Well... go back to the basics.

Maciej Los 9-Mar-18 4:53am

Ralf, you're genius!

Suren97 9-Mar-18 5:21am

I updated my code, you mean like this?

Ralf Meier 9-Mar-18 7:01am

No ... I meant it like OG allready has described :
- you don't need different Draw-Methods - you need one Draw-Method which works with a Variable instead of an assigned Constant.
- if you want to change the Color you only need to change the Assignment to this Variable (instead of using a 2nd Method).

I would not create a kind of 'Random-Color' because there are to much combinations which makes absolut senseless Colors (which means : Colors are to near together or not good to be seen on the Background).

Suren97 9-Mar-18 7:06am

How can i change the assignment to this variable?

OriginalGriff 9-Mar-18 7:25am

You are kidding, right?
You don't know how to use the assignment operator?

myVariable = newValue;

Suren97 9-Mar-18 7:29am

Then????????

OriginalGriff 9-Mar-18 7:39am

Then what?

Suren97 9-Mar-18 7:43am

where should i declare it?

Suren97 9-Mar-18 7:44am

in Ball Class?

Suren97 9-Mar-18 8:09am

I updated my code, like this?

Ralf Meier 9-Mar-18 8:36am

Yes ... perhaps like that. It would change the Color each time the Ball is draw again ...

But I would not create Random-Colors - you often will get Colors which are near together or near to the Background-Color ...

Suren97 9-Mar-18 8:43am

But I need to change color of ball When the ball collides on the edges of the form,but in this case it changes constantly

Suren97 9-Mar-18 8:44am

How can i say that when the ball collides on the edges that time change color

Ralf Meier 9-Mar-18 9:09am

I don't have checked your code ...
I suppose you have a part in your code which checks the collision and changes the vector.
At that position where you do this calculation (and only there and only in this case) you should change the color-assignment ... (and not in your draw-method).
Because you now use a Variable for your color and not more a Constant you can change it's value everywhere you need (inside the class where it's defined).

Suren97 9-Mar-18 8:10am

I updated my code, like this?

CPallini 9-Mar-18 3:56am

5.