@Override
public Drawable getDrawable(Context context, String source, int width, int hight, Drawable defaultDrawable) 

@Override
public Drawable getDrawable(Context context, String source, int width, int hight, Drawable defaultDrawable) {
    //接入方接入自己的ImageLoader
    //示例代码里使用开源的universalimageloader
    UniversalDrawable drawable = new UniversalDrawable();
    if (TextUtils.isEmpty(source)) {
        return drawable;
    }
    drawable.loadImage(context, source);
    return drawable;
}