Question

I am creating a 2d side scrolling(kinda) game for the windows phone in C# and XNA.

I have a character animation that makes it look like the sprite is moving, however the background and enemies are the only things moving.
I have loaded the texture for the enemy and the position on the screen is static so that’s fine.
But my problem is, I want to spawn these enemies at random intervals.
I have set up a random number generator, an int and a couple TimeSpan variables.

Here is the code I have placed in the UpdateEnemies method.

Note: in Update, I am calling UpdateEnemies(gameTime);

random = new Random();
spawnSeconds = random.Next(1, 6);
enemySpawnTime = TimeSpan.FromSeconds(spawnSeconds); 
if (gameTime.TotalGameTime - previousSpawnTime > enemySpawnTime)
{
    previousSpawnTime = gameTime.TotalGameTime;
    // Add an Enemy
    AddEnemy();
}

I am having an issue here as the enemies spawning is not random. They spawn at the same interval for that particular run.

I have used Breakpoints and the spawnSeconds and enemySpawnTime update fine everytime but still this issue.

Any help would be greatly appreciated.

Answer 1

Assuming UpdateEnemies is called on every Update(), you are changing enemySpawnTime on every Update(), which doesn’t make sense. You should only change it when an enemy spawns, i.e.:

if (gameTime.TotalGameTime - previousSpawnTime > enemySpawnTime)
{
    // Add an Enemy
    AddEnemy();

    // Update the time left next enemy spawn
    previousSpawnTime = gameTime.TotalGameTime;
    var spawnSeconds = random.Next(1, 6); // random should be a member of the class
    enemySpawnTime = TimeSpan.FromSeconds(spawnSeconds); 
}

And as noted previously, only create the Random() object once, for example in Initialize(), and make it a member of the class.