help with tile map

Monkey Forums/Monkey Beginners/help with tile map

dubbsta

(Posted 2016) [#1]

looked at different codes and trying to understand tile maps, 2d arrays and matricies, but having a little trouble. I managed to get this to load but "error null object access" keeps happening. for some reason i have to put field bg on both calsses or i get error bg not declared. pls help have to understan tile maps.
should i have went with screen width divide by tile size idk

also can someone point me to scrolling single image background

heres the code.

    

Import mojo


Class Mygame Extends App


global  level:Level


Field width:Int = 320
Field hieght:Int =240
Global bg:Image





Method OnCreate()

   SetUpdateRate(60)
        
        level= New Level()

		bg = LoadImage("level.png",128,128,8,Image.MidHandle)



End 



Method OnUpdate()
   
End 



Method OnRender()

Cls(0,0,0)


  level.Draw()


 End                           


End


Class Level

Field tileH:Int =128
Field tileW:Int =128
field bg:Image
Field cols:Int = 5
Field rows:Int = 3
Field map:Int [][]= [[1,1,1,1,1],
                      [2,2,2,2,2],       
                      [3,6,2,5,4]]


 
  Method Draw:Void()


     For Local i:Int = 0 until rows
       For Local j:Int = 0 until cols 
   
        If map[i][j] =1 Then DrawImage (bg,i*tileW,j*tileH,1)
    
     
    		'Select  map[i][j] 
    			'Case 1
        		'	DrawImage (bg,i*tileW,j*tileH,1)
    		' End 
     End 
        End 
   	
   	
   End  
   
End 

    
Function Main:int()
   New Mygame
End

Jesse

(Posted 2016) [#2]

Putting a global variable inside a class makes the variable global only to the class. it means that you can only access it from methods and functions with in that class. your "bg" variable is only directly accessible from "MyGame" class. to access it from any other class you need to pass it as a parameter to that class functions or methods or create the global outside any individual class. having the same global in two different classes only means that both are two completely different variables.

dubbsta

(Posted 2016) [#3]

success!!! that did it jesse thanks. i did know about that but forgot hehe. thanks for pointing that out!

Whiteball

(Posted 2016) [#4]

I thought globals where scoped to the module, ie. anything in the current file has access?

Jesse

(Posted 2016) [#5]

Globals outside classes are accessible to classes, methods and function of any other file the uses the file that contain the Global.
Globals within Classes are only accessible "directly" to methods and function with in the class. class globals can be access from outside the the class by prefixing it with the class name or an instance of the class:
MyClass.MyGlobal
or
myClassInstance.MyGlobal"