Keys do not work while using Keys.Down (Or up, left, right)

Question

I am a beginner at C# (C Sharp) and I couldn't figure out why my Arrow keys would not work. Can anyone help me? Note: I am a beginner, I have been working at this for a while now and I can't figure it out. I have tried researching it with no luck, I hope I don't bother you. When I try and move it it doesn't work.

Here is my Form1

public partial class Form1 : Form
{
    Graphics paper;
    Snake snake = new Snake();

    bool left = false;
    bool right = false;
    bool down = false;
    bool up = false;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Paint(object sender, PaintEventArgs e)
    {
        paper = e.Graphics;
        snake.drawSnake(paper);
    }

    private void Form1_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyData == Keys.Down && up == false)
        {
            down = true;
            up = false;
            right = false;
            left = false;
        }
        if (e.KeyData == Keys.Up && down == false)
        {
            down = false;
            up = true;
            right = false;
            left = false;
        }
        if (e.KeyData == Keys.Right && left == false)
        {
            down = false;
            up = false;
            right = true;
            left = false;
        }
        if (e.KeyData == Keys.Left && right == false)
        {
            down = false;
            up = false;
            right = false;
            left = true;
        }
    }

    private void timer1_Tick(object sender, EventArgs e)
    {
        if (down) { snake.moveDown(); }
        if (up) { snake.moveUp(); }
        if (right) { snake.moveRight(); }
        if (left) { snake.moveLeft(); }

        this.Invalidate();
    }
 }

} Here is my Snake class if you need it.

{

    public Snake()
    {
        snakeRec = new Rectangle[3];
        brush = new SolidBrush(Color.Blue);

        x = 20;
        y = 0;
        width = 10;
        height = 10;

        for(int i = 0; i < snakeRec.Length; i++)
        {
            snakeRec[i] = new Rectangle(x, y, width, height);
            x -= 10;
        }
    }
    public void drawSnake(Graphics paper)
    {
        foreach (Rectangle rec in snakeRec)
        {
            paper.FillRectangle(brush, rec);
        }
    }

    public void drawSnake()
    {
        for (int i = snakeRec.Length - 1; i > 0; i--)
        {
            snakeRec[i] = snakeRec[i - 1];
        }
    }

    public void moveDown()
    {
        drawSnake();
        snakeRec[0].Y += 10;
    }
    public void moveUp()
    {
        drawSnake();
        snakeRec[0].Y -= 10;
    }
    public void moveRight()
    {
        drawSnake();
        snakeRec[0].X += 10;
    }
    public void moveLeft()
    {
        drawSnake();
        snakeRec[0].X -= 10;
    }
}

}

As I said I really am a beginner and I learn by looking, is there a way you could show me? — That One Dude, Nov 19 '13 at 23:01
Can you tell us what exactly is not working? The snake can be controlled when the code is executed. — keenthinker, Nov 19 '13 at 23:05
When I debug it, I can not move the snake using my arrow keys. I hope I am not derping up. For me the snake can NOT be controlled. — That One Dude, Nov 19 '13 at 23:06
I think while in the debugger, the windows is not repainted, so your code is working, but you are not able to see the progress. This is somehow a catch with WinForm UI's and debugging - window is not repainted. Try your program without the debugger at first. Maybe [this explanation on SO](http://stackoverflow.com/questions/15255078/gui-does-not-redraw-while-stepping-in-debug-mode) could help - it addresses the issue. — keenthinker, Nov 19 '13 at 23:14
@pasty It just won't repaint it. I don't know why it might do this though. — That One Dude, Nov 19 '13 at 23:19

score 1 · Accepted Answer · answered Nov 19 '13 at 23:10

1

I tried your code and it works well, so this is the only thing I can think of:

private void Form1_Load(object sender, EventArgs e)
{
   timer1.Enabled = true;
}

Make sure that big guy is enabled.

answered Nov 19 '13 at 23:10

Hanlet Escaño

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I thought of the same, but it could be that it is started directly from the properties. – keenthinker Nov 19 '13 at 23:12
:P I've got it enabled. Still doesn't work. It doesn't move when I click the arrow keys. – That One Dude Nov 19 '13 at 23:13
@user3002617 I know the method works (change the Text of the form inside the tick event and you will see the title bar changing). So maybe it is not drawing it right? – Hanlet Escaño Nov 19 '13 at 23:14
@user3002617 it is working fine for me. Make sure all of your events are bound correctly (redrawing the snake and everything, is actually cool :D) – Hanlet Escaño Nov 19 '13 at 23:20
@HanletEscaño Thanks! What do you mean by "Make sure all of your events are bound correctly"? – That One Dude Nov 19 '13 at 23:22
AHA! I figured it out. My KeyDown "Event" I guess was not linked to my Form1_KeyDown, thank you all for your help. Derp! – That One Dude Nov 19 '13 at 23:26
@user3002617 that's exactly what I meant, that each event was "bound", or wired up correctly. – Hanlet Escaño Nov 19 '13 at 23:26

score 0 · Answer 2 · answered Nov 19 '13 at 23:25

Don't hold on to the Graphics from the Paint() event like that. Just pass e.Graphics directly to your Draw() method like this:

    private void Form1_Paint(object sender, PaintEventArgs e)
    {
        snake.drawSnake(e.Graphics);
    }

Also, make sure the Paint() event of the Form is wired up. Select the Form. Now click the "Lightning" Bolt" icon in the Properties Pane (bottom right by default). Find the Paint entry and change the dropdown to the right to "Form1_Paint".

Keys do not work while using Keys.Down (Or up, left, right)

2 Answers2