Problems drawing images form another class

Question

Ok as the title says I'm having trouble drawing images from a different class. I have a class that represents a plane and it has a draw' method that draws its .gif image.
public void draw (Graphics g)
g.drawImage(planepic , xPos, yPos, null)
then in my main class in the paint method i have
plane.draw(g);
I think my problem is the null for my image observer. I tried using null as my image observer and i got a error saying i can't make a static reference to a non static method.
I've done some research because i never really understood static but i still don't quite get it.
Also when I use this as my image observer i get a error in my plane object.
I also just tried passing and making a object for my main class and i still got the static error.
Any help is appreciated and thanks in advance

Answer 1

Ok as the title says I'm having trouble drawing
images from a different class. I have a class that
represents a plane and it has a draw' method that
draws its .gif image.
public void draw (Graphics g)
g.drawImage(planepic , xPos, yPos, null)
in my main class in the paint method i have
plane.draw(g);
I think my problem is the null for my image observer.
I tried using null as my image observer and i got a
error saying i can't make a static reference to a non
static method. Use a minimal implementation of the ImageObserver to be sure.
public class Plane implements ImageObserver
public boolean imageUpdate(
Image img,int infoFlags,int x,int y,int width,int height)
   switch(infoFlags)
      case ALLBITS:
                return false;
      case SOMEBITS:
                return true;
      default:
            return true;
I've done some research because i never really
understood static but i still don't quite get it.
Also when I use this as my image observer i get a
error in my plane object.
I also just tried passing and making a object for my
main class and i still got the static error.
Any help is appreciated and thanks in advanceWhen you call draw(g) from your other class you hand it a Graphics context that you instantiated somewhere else ie: in another class. Without a more complete example it is really impossible to determine your issue for sure,
but if I was to guess I would say you need to make sure that the Graphics context handed to the draw(Graphics) method was instantiated from a Component that was already visible. ie: Do a f
Frame.createImage() from your parent frame after iyou have already called setVisible(true); In other words I suspect you are making and Image from some other Component that is not yet visible. That however is a guess so if not the issue post the rest of the code or at least a minimal implementation that demonstrates this.
About static:
static means the class/variable is the same throughout ALL classes of that type and if changed in one instance it will change and thus be the same for all instances.
You CAN call static by referencing the base class Object without having to instantiate.
ie:given
public class SomeClass
static String name;
static String getName
   if(name == null)
      name = "DefaultName";
   return name;
}Thus you could call..
  String name = SomeClass.getName();As opposed to
SomeClass myClass = new SomeClass();
      myClass.getName();This can get you in trouble if you try to make a method that is static
that then tries to reference non static variables.
ie:
public class SomeClass
int x;
static String name;
SomeClass()
   x=0;
static String getName
   if(name == null)
      name = "DefaultName";
   x++;
   return name;
}In this case SomeClass.getName(); will throw and exception because it is trying to access[b] x  from a static context .
Hope that clears that up for you; if not post a more complete example.
Good Luck!
(T)