java跨类使用资源？

Question

我有一个GameLoop类，其中定义了ParticleSystem对象

ParticleSystem包含一组粒子对象——我不想为每个单独的粒子加载一个图像，我只想能够从GameLoop类中的源图像中绘制——我怎样才能高效地做到这一点

解决方案：

以下是Dan S帮我想到的：

public class ResourceManager  {

Context mContext;   

public final HashMap<String, Bitmap> Texture = new HashMap<String, Bitmap>();

//Constructor
public ResourceManager(Context context)
{       
    mContext = context;
    Texture.put("particle1", loadBitmap(R.drawable.particle1));
}

public Bitmap getBitmap(String key)
{   
return Texture.get(key);
}

 /** Load an image */
    protected Bitmap loadBitmap(int id) { return   BitmapFactory.decodeResource(mContext.getResources(), id); }

  } //End ResourceManager

然后在类中定义它：

rm = new ResourceManager(mContext);

然后向下传递rm变量：

    ParticleSystem.Draw(rm, canvas);
   {
     Particle.Draw(rm, canvas);
    }

在粒子类中，我在构造函数中设置了一个字符串assetKey，这样我就可以通过一个名称来引用位图：

public void doDraw(ResourceManager rm, Canvas canvas) {
    canvas.drawBitmap(rm.getBitmap(AssetKey), xpos, ypos, null);
}

我希望这对其他人也有帮助

Answer 1

在GameLoop的构造函数中，创建位图并在其中保留对它们的引用，将它们设置为最终变量，以增加对意外赋值的保护。无论何时创建新粒子系统，都要将它们传递给构造函数或使用适当的setter方法进行设置

示例：

// in GameLoop definition

private Bitmap particleA;
private Bitmap particleB;

// somewhere in GameLoop constructor
particleA = BitmapFactor.decodeResource (activity.getResources(), R.drawable.particle_a);
particleB = BitmapFactor.decodeResource (activity.getResources(), R.drawable.particle_b);

// where you build your particle
Particle (GameLoop gl, ...) {
   oneLevelDown = new OneLevelDown(GameLoop gl, ...);
}

OneLevelDown (GameLoop gl, ...) {
   twoLevelDown = new TwoLevelDown(GameLoop gl, ...);
}

TwoLevelDown (GameLoop gl, ...) {
   particleABitmap = gl.getParticleA(); // simple getter
   particleBBitmap = gl.getParticleB(); // simple getter
}

继续传递GameLoop直到你完成。这可能感觉效率不高，但一旦你掌握了窍门，你会喜欢的，也可以看看这篇关于Dependency Injection的文章

Java内存使用示例：

class Car{
   public int year;
   public int name;
}

// Object variables are references to an object's data.

Car a = new Car(); // first car object and variable. 
a.year = 1990;
a.name = "Sam";

Car b = new Car();// second car object and variable
b.year = 2000;
b.name = "Bob";

Car c = a; // third car **variable** but same car object as **a**

// primitives are different

int a = 23; // first variable, 4 bytes used
int b = 45; // second variable, 4 bytes used (and a total of 8)
int c = a;  // third variable, 4 bytes used (and a total of 12). c took on the value of a, but does not point to the same memory as a