How to interpret Debugging information?
<p>This is actually two questions.  The first relates to my program, and the second is a more general question regarding debugging.</p>

<p>In my code, I have two button listeners.  When the first is clicked, the onClickListener creates the locationlistener, as well as the LocationManager which requests updates from the locationlistener.  (See below...)  </p>

<pre><code>LocationManager locationManager = (LocationManager)  getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationlistener);
</code></pre>

<p>On the click of the second button, I try to unregister the listener as follows... </p>

<p>locationManager.removeUpdates(locationlistener);</p>

<p>However, I end up with a force close and the following info in the debugger...</p>

<pre><code>ERROR/AndroidRuntime(310): FATAL EXCEPTION: main
ERROR/AndroidRuntime(310): java.lang.NullPointerException
ERROR/AndroidRuntime(310):     at com.ryan.gcal.GRunCal$2.onClick(GRunCal.java:94)
ERROR/AndroidRuntime(310):     at android.view.View.performClick(View.java:2408)
ERROR/AndroidRuntime(310):     at android.view.View$PerformClick.run(View.java:8816)
ERROR/AndroidRuntime(310):     at android.os.Handler.handleCallback(Handler.java:587)
ERROR/AndroidRuntime(310):     at android.os.Handler.dispatchMessage(Handler.java:92)
ERROR/AndroidRuntime(310):     at android.os.Looper.loop(Looper.java:123)
ERROR/AndroidRuntime(310):     at android.app.ActivityThread.main(ActivityThread.java:4627)
ERROR/AndroidRuntime(310):     at java.lang.reflect.Method.invokeNative(Native Method)
ERROR/AndroidRuntime(310):     at java.lang.reflect.Method.invoke(Method.java:521)
ERROR/AndroidRuntime(310):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
ERROR/AndroidRuntime(310):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
ERROR/AndroidRuntime(310):     at dalvik.system.NativeStart.main(Native Method)
</code></pre>

<p>Line 94 of my code, where the error originates, is where I tried to remove the location listener.  So I assume I am not removing the location listener properly, but I am not sure what is wrong.  My LocationManager is declared at the start of my code...</p>

<pre><code>Locationmanager locationManager;
</code></pre>

<p>My first question is, what am I doing wrong in removing the listener? And secondly, can anyone provide some tips/advice on learning to interpret debug errors meaningfully? Thanks.</p>
