title: Android Development: "thread exiting with uncaught exception"
body: <p>I'm trying to create my first Android App (a game) but I'm having some difficulties getting started.</p>
  
  <p>When I run my code I get this error log:</p>
  
  <pre><code>05-25 02:41:51.022: WARN/dalvikvm(634): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634): FATAL EXCEPTION: main
  05-25 02:41:51.040: ERROR/AndroidRuntime(634): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.stickfigs.nmg/com.stickfigs.nmg.NMG}: java.lang.NullPointerException
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.os.Handler.dispatchMessage(Handler.java:99)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.os.Looper.loop(Looper.java:123)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.main(ActivityThread.java:4627)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at java.lang.reflect.Method.invokeNative(Native Method)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at java.lang.reflect.Method.invoke(Method.java:521)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at dalvik.system.NativeStart.main(Native Method)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634): Caused by: java.lang.NullPointerException
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at com.stickfigs.nmg.NMG.onCreate(NMG.java:32)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
  05-25 02:41:51.040: ERROR/AndroidRuntime(634):     ... 11 more
  05-25 02:41:51.062: WARN/ActivityManager(59):   Force finishing activity com.stickfigs.nmg/.NMG
  </code></pre>
  
  <p>I think the problem is this "thread exiting with uncaught exception" part, I have no idea what the exception could be or what's causing it.</p>
  
  <p>Here is my code:</p>
  
  <p><strong>NMGView.java:</strong>
      package com.stickfigs.NMG;</p>
  
  <pre><code>import android.content.Context;
  import android.os.Bundle;
  import android.util.AttributeSet;
  import android.view.SurfaceHolder;
  import android.view.SurfaceView;
  
  class NMGView extends SurfaceView implements SurfaceHolder.Callback {
  
      class NMGThread extends Thread {
          //State-tracking constants
          public static final int STATE_LOSE = 1;
          public static final int STATE_PAUSE = 2;
          public static final int STATE_READY = 3;
          public static final int STATE_RUNNING = 4;
          public static final int STATE_WIN = 5;
  
          /** The state of the game. One of READY, RUNNING, PAUSE, LOSE, or WIN */
          private int mode;
  
          /** Handle to the surface manager object we interact with */
          private SurfaceHolder surfaceHolder;
  
          public NMGThread(SurfaceHolder surfaceHolderc, Context contextc) {
              // get handles to some important objects
              surfaceHolder = surfaceHolderc;
              context = contextc;
  
          }
  
          /**
           * Restores game state from the indicated Bundle. Typically called when
           * the Activity is being restored after having been previously
           * destroyed.
           * 
           * @param savedState Bundle containing the game state
           */
          public synchronized void restoreState(Bundle savedState) {
              synchronized (surfaceHolder) {
                  setState(STATE_PAUSE);
                  }
          }
  
          /**
           * Sets the game mode. That is, whether we are running, paused, in the
           * failure state, in the victory state, etc.
           * 
           * @param mode one of the STATE_* constants
           * @param message string to add to screen or null
           */
          public void setState(int modec) {
              synchronized (surfaceHolder) {
                  mode = modec;
              }
          }
      }
  
      @Override
      public void surfaceChanged(SurfaceHolder holder, int format, int width,
              int height) {
          // TODO Auto-generated method stub
  
      }
  
      @Override
      public void surfaceCreated(SurfaceHolder holder) {
          // TODO Auto-generated method stub
  
      }
  
      @Override
      public void surfaceDestroyed(SurfaceHolder holder) {
          // TODO Auto-generated method stub
  
      }
  
      /** Handle to the application context, used to e.g. fetch Drawables. */
      private Context context;
  
      /** The thread that actually draws the animation */
      private NMGThread thread;
  
      public NMGView(Context context, AttributeSet attrs) {
          super(context, attrs);
  
          // register our interest in hearing about changes to our surface
          SurfaceHolder holder = getHolder();
          holder.addCallback(this);
  
          // create thread only; it's started in surfaceCreated()
          thread = new NMGThread(holder, context);
  
          setFocusable(true); // make sure we get key events
      }
  
      /**
       * Fetches the animation thread corresponding to this LunarView.
       * 
       * @return the animation thread
       */
      public NMGThread getThread() {
          return thread;
      }
  }
  </code></pre>
  
  <p><strong>NMG.java:</strong></p>
  
  <pre><code>package com.stickfigs.nmg;
  
  import android.app.Activity;
  import android.os.Bundle;
  import android.util.Log;
  import android.view.Window;
  
  import com.stickfigs.nmg.NMGView.NMGThread;
  
  public class NMG extends Activity {
      /** Called when the activity is first created. */
  
      /** A handle to the thread that's actually running the animation. */
      private NMGThread nMGThread;
  
      /** A handle to the View in which the game is running. */
      private NMGView nMGView;
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
  
          //Turn off the window's title bar
          // TODO Turn off the status bar
          requestWindowFeature(Window.FEATURE_NO_TITLE);
  
          // tell system to use the layout defined in our XML file
          setContentView(R.layout.nmg_layout);
  
          // get handles to the LunarView from XML, and its LunarThread
          nMGView = (NMGView) findViewById(R.id.nmg);
          nMGThread = nMGView.getThread();
  
          if (savedInstanceState == null) {
              // we were just launched: set up a new game
              nMGThread.setState(NMGThread.STATE_READY);
              Log.w(this.getClass().getName(), "SIS is null");
          } else {
              // we are being restored: resume a previous game
              nMGThread.restoreState(savedInstanceState);
              Log.w(this.getClass().getName(), "SIS is nonnull");
          }
      }
  }
  </code></pre>
  
  <p>UPDATE: Here is my R.java and nmg_layout.xml:</p>
  
  <p><strong>R.java:</strong>
      package com.stickfigs.nmg;</p>
  
  <pre><code>public final class R {
      public static final class attr {
      }
      public static final class drawable {
          public static final int icon=0x7f020000;
      }
      public static final class id {
          public static final int nmg=0x7f050000;
      }
      public static final class layout {
          public static final int nmg_layout=0x7f030000;
      }
      public static final class string {
          public static final int app_name=0x7f040001;
          public static final int hello=0x7f040000;
      }
  }
  </code></pre>
  
  <p><strong>nmg_layout.xml:</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"&gt;
  
      &lt;com.stickfigs.nmg.NMGView
        android:id="@+id/nmg"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/&gt;
  &lt;/FrameLayout&gt;
  </code></pre>