Question

I am creating an Android board game similar to, for example, Bubble Pop where I need to use several bitmaps multiple times.

I have a list of Stones (10×10), where each Stone is an object which holds its bitmap and some other values. Lot of bitmaps (stone colors) are same.

Right now i am using something like this for every Stone in the list:

public class Stone extends Point{

  private Bitmap mImg;

  public Stone (int x, int y, Resources res, Stones mStone) {
    ...
    mImg = BitmapFactory.decodeResource(mRes, mStone.getId());
  }

  protected void changeColor(Stones newD){
      mStone = newD;
      mImg = BitmapFactory.decodeResource(mRes, mStone.getId());
    }
  }

I found several similar questions, but it is all about big bitmaps. Also i found some Android documentation about caching images, but i am not sure if it solves my problem and how to share this cache between all my stones.

What is the best practice, to achive good performance and avoid OutofMemoryError?

Answer 1

You probably don’t need cache. Since you should have a limited number of stone colors (thus bitmaps) you can consider holding those graphic assets in one single class (probably static global class or through singleton pattern.

In your Stone class, you just need to hold the stone’s color Id and get the drawable from your assets class. (you can save bitmap, but drawable is much more efficient and you may easily change it to allow some animation later)

For example:

// Singleton - look at the link for the suggested pattern
public class GraphicAssets {
    private Context mContext;
    private Hashtable<Integer, Drawable> assets;

    public Drawable getStone(int id){
        if (assets.containsKey(id)) return assets.get(id);

        // Create stone if not already load - lazy loading, you may load everything in constructor
        Drawable d = new BitmapDrawable(BitmapFactory.decodeResource(mContext.getResources(), id));
        assets.put(id, d);
        return d;
    }

}