public HorizontallyScrollingBackground(Viewport theViewport)
{
mBackgroundSprites = new List <BackgroundSprite>();
mRightMostSprite = null;
mLeftMostSprite = null;
mViewport = theViewport;
}
//Adds a background sprite to be scrolled through the screen
public void AddBackground(string theAssetName)
{
BackgroundSprite aBackgroundSprite = new BackgroundSprite();
aBackgroundSprite.AssetName = theAssetName;
mBackgroundSprites.Add(aBackgroundSprite);
}
//Update the posotin of the background images
public void Update(GameTime theGameTime, int theSpeed, HorizontalScrollDirection theDirection)
{
if (theDirection == HorizontalScrollDirection.Left)
{
//Check to see if any of the Background sprites have moved off the screen
//if they have, then move them to the right of the chain of scrolling backgrounds
foreach (BackgroundSprite aBackgroundSprite in mBackgroundSprites)
{
if (aBackgroundSprite.Position.X < mViewport.X - aBackgroundSprite.Size.Width)
{
aBackgroundSprite.Position = new Vector2(mRightMostSprite.Position.X + mRightMostSprite.Size.Width, mViewport.Y);
mRightMostSprite = aBackgroundSprite;
}
}
}
else if (theDirection == HorizontalScrollDirection.Right)
{
//Check to see if any of the background images have moved off the screen
//if they have, then move them to the left of the chain of scrolling backgrounds
foreach (BackgroundSprite aBackgroundSprite in mBackgroundSprites)
{
if (aBackgroundSprite.Position.X > mViewport.X + mViewport.Width)
{
aBackgroundSprite.Position = new Vector2(mLeftMostSprite.Position.X - mLeftMostSprite.Size.Width, mViewport.Y);
mLeftMostSprite = aBackgroundSprite;
}
}
}
//Set the Direction based on movement to the left or right that was passed in
Vector2 aDirection = Vector2.Zero;
if (theDirection == HorizontalScrollDirection.Left)
{
aDirection.X = -1;
}
else if (theDirection == HorizontalScrollDirection.Right)
{
aDirection.X = 1;
}
//Update the postions of each of the Background sprites
foreach (BackgroundSprite aBackgroundSprite in mBackgroundSprites)
{
aBackgroundSprite.Update(theGameTime, new Vector2(theSpeed, 0), aDirection);
}
}
public void LoadContent(ContentManager theContentManager)
{
//Clear the Sprites currently stored as the left and right ends of the chain
mRightMostSprite = null;
mLeftMostSprite = null;
//The total width of all the sprites in the chain
float aWidth = 0;
//Cycle through all of the Background sprites that have been added
//and load their content and position them.
foreach (BackgroundSprite aBackgroundSprite in mBackgroundSprites)
{
//Load the sprite's content and apply it's scale, the scale is calculate by figuring
//out how far the sprite needs to be stretech to make it fill the height of the viewport
aBackgroundSprite.LoadContent(theContentManager, aBackgroundSprite.AssetName);
aBackgroundSprite.mScale = mViewport.Height / aBackgroundSprite.Size.Height;
//If the Background sprite is the first in line, then mLastInLine will be null.
if (mRightMostSprite == null)
{
//Position the first Background sprite in line at the (0,0) position
aBackgroundSprite.Position = new Vector2(mViewport.X, mViewport.Y);
mLeftMostSprite = aBackgroundSprite;
}
else
{
//Position the sprite after the last sprite in line
aBackgroundSprite.Position = new Vector2(mRightMostSprite.Position.X + mRightMostSprite.Size.Width, mViewport.Y);
}
//Set the sprite as the last one in line
mRightMostSprite = aBackgroundSprite;
//Increment the width of all the sprites combined in the chain
aWidth += aBackgroundSprite.Size.Width;
}
//If the Width of all the sprites in the chain does not fill the twice the Viewport width
//then we need to cycle through the images over and over until we have added
//enough background images to fill the twice the width.
int aIndex = 0;
if (mBackgroundSprites.Count > 0 && aWidth < mViewport.Width * 2)
{
do
{
//Add another background image to the chain
BackgroundSprite aBackgroundSprite = new BackgroundSprite();
aBackgroundSprite.AssetName = mBackgroundSprites[aIndex].AssetName;
aBackgroundSprite.LoadContent(theContentManager, aBackgroundSprite.AssetName);
aBackgroundSprite.Scale = mViewport.Height / aBackgroundSprite.Size.Height;
aBackgroundSprite.Position = new Vector2(mRightMostSprite.Position.X + mRightMostSprite.Size.Width, mViewport.Y);
mBackgroundSprites.Add(aBackgroundSprite);
mRightMostSprite = aBackgroundSprite;
//Add the new background Image's width to the total width of the chain
aWidth += aBackgroundSprite.Size.Width;
//Move to the next image in the background images
//If we've moved to the end of the indexes, start over
aIndex += 1;
if (aIndex > mBackgroundSprites.Count - 1)
{
aIndex = 0;
}
} while (aWidth < mViewport.Width * 2);
}
}
