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Android game loop issues


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#1 Sollum   GDNet+   -  Reputation: 759

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Posted 19 March 2013 - 01:57 AM

Hello,

 

I am not sure if this is right place to post, but question is rather simple, so i think it goes well here.

 

Maybe someone has some sort of schema or could explain Android application life cycle?

 

When making a game, I use standard cycle

 

Loop begin

    Input

    Logic

    Output

Loop end

 

 

Problem i stumbled upon is that Android apps starts with activity and later on, magic happens.

GLViewSurface (or something along those lines) draws whenever he wants and thus i have to write manual checks in frame drawing function, it was called "onFrameDraw" if am right. And input handling acts on his own in activity. So in the end i had to write some additional classes to split these layers, but one problem remains.

 

It goes something along these lines

 

 

 

public void onFrameDraw()
{
    if (CheckIfFPSAllowsMeToDoSomethingNow())
    {
         handleInputEvents();
         handleLogics();
         feelFreeToDrawStuff();
    }
}
 

 

It's not that i mind it, but i don't think its appropriate to call input event handling and logic from context of drawing method.

 

Maybe someone has any tips or any schema on that matter?



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#2 JoeJ   Members   -  Reputation: 259

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Posted 19 March 2013 - 03:42 AM

You should consider adding multithreading from start on - it was some work for me to add it later.

Because on mobiles calls to OGL do not return until the GPU finished its job, even single cores benefit from it.

 

For me it looks somehow like this (i've all that in one class/file, if you wanna keep Java as less as possible):

 

 

 

float accelV[3]; // global sensor data

 

PhysicsThreadFunc () // called from thread 1

{

      if update request flag -> do physics using accelV, game logic, setup render stuff and store results

}

 

GraphicsThread () // onFrameDraw called from thread 2

{

      if results are ready, copy them, render and set request flag // while rendering (CPU mostly waiting), next physics step executes in parallel

}

 

AcceleromaterMessage () // called frequently from thread 3 - you can set the update rate only by symbolic definitions ('GAME', 'FASTEST'...)

{

      accelV[0] = ... // simply update - writing a float is atomic, so no need to synchronize with simultaneous read access from other threads

}



#3 JoeJ   Members   -  Reputation: 259

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Posted 19 March 2013 - 04:08 AM

Edit: "i've all that in one class/file, if you wanna keep Java as less as possible" means:

I use only one activity (GLViewSurface), and generate the second thread within that - so only one activity but multiple thread.

 

Some personal advice: Understanding lifecycle is somehow frustrating - don't mix that stuff with your game code - don't divide your game code in a way you think android might request.

Keep the interface between OS and game as small as possible. That way the game keeps portable and fun developing, while the frustrating OS section keeps small and exchangeable :)



#4 Sollum   GDNet+   -  Reputation: 759

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Posted 19 March 2013 - 12:00 PM

Hmmm, thanks for the tips!

 

For now i'll try to refrain from using threads.

 

Edit:

Do GLSurfaceView.Renderer and Activity start in different threads?

 

Because i stumbled upon that ugly problem ConcurentModificationException in a list.

 

Wrote some locks, but frankly... they look bad >.<

 

 

 

private boolean bIIA_ListLocked;

public boolean isIIALLocked()
{
   return bIIA_ListLocked;
}


public void lockIIAL()
{
   bIIA_ListLocked = true;
}


public void unlockIIAL()
{
   bIIA_ListLocked = false;
}


public void manageEvents()
{
   if (!isIIALLocked())
   {
      lockIIAL();

      for (InterfaceInputAction IIA : IIA_List)
      {
         System.out.println(IIA.getSource() + " " + IIA.getAction());
      }

      IIA_List.clear();

      unlockIIAL();
   }
}


private void addInputEvent(InterfaceInputAction IIA)
{
   if (!isIIALLocked())
   {
      lockIIAL();

      IIA_List.add(IIA);

      unlockIIAL();
   }
}
 

Edited by Sollum, 19 March 2013 - 03:43 PM.





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