Question

I’m making a simple 2d game for the android platform, which works perfectly from version 2.0 and above, but when testing it on a 1.6 device, it crashes immediately. On running the debugger, it seems that I’m getting a null pointer exception in the thread class. I was just wondering if anybody has any ideas as to where the problem might be.

Here’s the code for the thread class:

package com.marcusortiz.burnination;

import android.graphics.Canvas;
import android.view.SurfaceHolder;

public class GameThread extends Thread
{
  private SurfaceHolder sHolder;
  private MainView panel;
  private boolean isRunning;

  public GameThread(SurfaceHolder sHolder, MainView panel)
  {
    this.sHolder = sHolder;
    this.panel = panel;
  }

  public void setRunning(boolean isRunning)
  {
    this.isRunning = isRunning;
  }

  public SurfaceHolder getSurfaceHolder()
  {
    return sHolder;
  }

  @Override
  public void run()
  {
    Canvas canvas;
    while(isRunning)
    {
      canvas = null;
      try
      {
        canvas = sHolder.lockCanvas(null);
        synchronized(sHolder)
        {
          for(Sprite s : panel.getSprites())
          {
            s.update();
          }
          panel.onDraw(canvas);
        }
      }
      finally
      {
        if(canvas != null)
        {
          sHolder.unlockCanvasAndPost(canvas);
        }
      }
    }
  }
}

Maybe there’s some compatibility issues with this code that I’m not aware of–I’m very much a beginner when it comes to using threads.

EDIT: here’s the requested stack trace

burnination [Android Application]   
  DalvikVM[localhost:8608]  
    Thread [<3> main] (Running) 
    Thread [<15> Binder Thread #3] (Running)    
    Thread [<13> Binder Thread #2] (Running)    
    Thread [<11> Binder Thread #1] (Running)    
    Thread [<17> Thread-9] (Suspended (exception NullPointerException)) 
      GameThread.run() line: 53 

Answer 1

That’s not a stack trace, but it looks like the problem is on line 53, which is what I was trying to get at. It looks like the code you posted probably doesn’t like up exactly with what you’re running, because line 53 is a closing brace. There’s probably a variable on that line that’s null.