Process.Start opens too many browsers in XNA game

Question

I'm creating a game in XNA that runs on a PC.

On the splash screen, the user has three options. If they press "Enter" the game will begin, if they press "M" they'll go to the Help menu and if they press "W" I want that to take them to my website.

I'm using Process.Start to open the browser to my website.

The problem is that when I press "W", sometimes it will open 1 browser with the website. However, most of the time it will open anywhere from 3 - 7 browsers simultaneously.

Why is it opening multiple browsers simultaneously?

How do I make it open only 1 browser when "W" is pressed?

Here is my code. I haven't built my website yet, so I'm using yahoo.com as the destination:

 private void UpdateSplashScreen()
    {
        KeyboardState keyState = Keyboard.GetState();

        if (gameState == GameState.StartScreen)               
        {
            if (keyState.IsKeyDown(Keys.Enter))
            {
                gameState = GameState.Level1;
                explosionTime = 0.0f;
            }

            if (keyState.IsKeyDown(Keys.M))
            {
                gameState = GameState.HelpScreen;
            }

           if (keyState.IsKeyDown(Keys.W))
           {

             Process.Start("IExplore.exe", "www.yahoo.com");

           }
        }

Thanks,

Mike

score 3 · Answer 1 · answered Sep 21 '11 at 16:39

A common way to handle this is to always track the keyboard state from the previous frame. If a key wasn't down on the previous frame, but is down this frame then you know it was just pressed. If the key was down on the previous frame then you know it's being held down.

// somewhere in your initialization code
KeyboardState keyState = Keyboard.GetState();
KeyboardState previousKeyState = keyState;
...

private void UpdateSplashScreen()
{
    previousKeyState = keyState;     // remember the state from the previous frame
    keyState = Keyboard.GetState();  // get the current state

    if (gameState == GameState.StartScreen)               
    {
        if (keyState.IsKeyDown(Keys.Enter) && !previousKeyState.IsKeyDown(Keys.Enter))
        {
            gameState = GameState.Level1;
            explosionTime = 0.0f;
        }

        if (keyState.IsKeyDown(Keys.M) && !previousKeyState.IsKeyDown(Keys.M))
        {
            gameState = GameState.HelpScreen;
        }

       if (keyState.IsKeyDown(Keys.W) && !previousKeyState.IsKeyDown(Keys.W))
       {

         Process.Start("IExplore.exe", "www.yahoo.com");

       }
    }

I usually create a KeyPressed function which cleans things up a bit.

bool KeyPressed(Keys key)
{
  return keyState.IsKeyDown(key) && !previousKeyState.IsKeyDown(key);
}

I like this way better than the OPs "launchFlag" solution, because this way you don't have to deal with any logic to make the launchFlag false again once you close the window or after a certain period of time. — Benjamin, Sep 22 '11 at 03:49

score 1 · Answer 2 · answered Sep 21 '11 at 15:34

The code you are using runs about 60 times a second; you may only press your key down for 100ms or so but in that time it checks to see if W is pressed down about 7 times. As such, it opens a large number of browser windows.

Try recording a timestamp (using DateTime.Now) of when you open the browser and then check that a certain time has elapsed (~2 secs?) before allowing another window to be opened. Or, create a boolean flag that is set false by opening the browser, so the browser can be opened only once.

score 0 · Answer 3 · answered Sep 22 '11 at 00:44

Thanks guys, that's what the problem was.

Callum Rogers solution was the easiest:

I declared a boolean:

   bool launchFlag = false;

Then checked it and set it to true after the website launched.

   private void UpdateSplashScreen()
{
    KeyboardState keyState = Keyboard.GetState();

    if (gameState == GameState.StartScreen)               
    {
        if (keyState.IsKeyDown(Keys.Enter))
        {
            gameState = GameState.Level1;
            explosionTime = 0.0f;
        }

        if (keyState.IsKeyDown(Keys.M))
        {
            gameState = GameState.HelpScreen;
        }

       if (keyState.IsKeyDown(Keys.W))
       {

         if (launchFlag == false)
               {
                   Process.Start("IExplore.exe", "www.yahoo.com");
                   launchFlag = true;
               }
       }
    }

I held the W key down for 30 seconds and it launched just 1 browser!

Thanks,

Mike

What happens if they want to launch the browser again? You'll have to add code to deal with setting launchFlag to false again. What happens when you start adding other functionality that requires detecting keypress rather than keydown? You'll have to add launchFlags for each of those situations, along with the logic to reset them. Best practice is to use the previous key state method. — Dave Carlile, Sep 22 '11 at 15:43

Process.Start opens too many browsers in XNA game

3 Answers3