java - "Unfortunately <myApp> has Stopeed" after running for 45sec on Nexus4 -

i'm beginner in android app development. using eclipse develop simple bluetooth shaker app. tried on phone , runs fine 30 seconds. , closes saying "unfortunately theapp has stopped". app supposed switch on bluetooth shake , play beep sound(pop.mp3)

please help.

main.java>

public class blueactivity extends activity implements sensorlistener, oncompletionlistener  {  button a, b,d; edittext e; textview f;  protected final int id=1; bluetoothadapter bt;  public mediaplayer m;  private sensormanager sensormgr; private long lastupdate = -1; private float x, y, z; private float last_x, last_y, last_z; private static final int shake_threshold = 3000;  @override protected void oncreate(bundle savedinstancestate) {     requestwindowfeature(window.feature_no_title);     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_blue);      a=(button)findviewbyid(r.id.button1);     b=(button)findviewbyid(r.id.button2);     d=(button)findviewbyid(r.id.button3);     f=(textview)findviewbyid(r.id.textview1);       e=(edittext)findviewbyid(r.id.edittext1);     e.setfocusable(false);        b.setonclicklistener(new onclicklistener(){          @override         public void onclick(view v) {             // todo auto-generated method stub             string s = bt.getaddress();             e.settext(s);          }      });      a.setonclicklistener(new onclicklistener(){          @override         public void onclick(view v) {             // todo auto-generated method stub             intent = new intent(bluetoothadapter.action_request_discoverable);             startactivityforresult(i, id);         }      });      d.setonclicklistener(new onclicklistener(){          @override         public void onclick(view v) {             // todo auto-generated method stub              uri uri = uri.parse("http://www.gamerspitch.com");             intent in = new intent(intent.action_view, uri);             startactivity(in);           }      });      sensormgr = (sensormanager) getsystemservice(sensor_service);     boolean accelsupported sensormgr.registerlistener(this,sensormanager.sensor_accelerometer,         sensormanager.sensor_delay_normal);      bt= bluetoothadapter.getdefaultadapter();      if (!accelsupported) {         // on accelerometer on device         sensormgr.unregisterlistener(this,sensormanager.sensor_accelerometer);     }   }  protected void onpause() {     m = mediaplayer.create(this, r.raw.pop);     m.setoncompletionlistener(this);     if (sensormgr != null) {         sensormgr.registerlistener(this,sensormanager.sensor_accelerometer);          sensormgr = null;          }     if(bt.isenabled())         m.start();     super.onpause();  }   @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.blue, menu);     return true; }  @override public void onaccuracychanged(int sensor, int accuracy) {     // todo auto-generated method stub  }  @override public void onsensorchanged(int sensor, float[] values) {     // todo auto-generated method stub      if (sensor == sensormanager.sensor_accelerometer) {         long curtime = system.currenttimemillis();         // allow 1 update every 100ms.         if ((curtime - lastupdate)> 100) {         long difftime = (curtime - lastupdate);         lastupdate = curtime;          m = mediaplayer.create(this, r.raw.pop);         m.setoncompletionlistener(this);           x = values[sensormanager.data_x];         y = values[sensormanager.data_y];         z = values[sensormanager.data_z];          float speed=math.abs(x+y+z - last_x - last_y - last_z)/ difftime*10000;          if (speed > shake_threshold) {             // yes, shake action! it!             //toast.maketext(this, "shaking", toast.length_short).show();              if(!bt.isenabled())             {                 bt.enable();                 f.settext("on");                 m.start();              }             else             {                 bt.disable();                 f.settext("off");             }           }         last_x = x;         last_y = y;         last_z = z;         }     }  }  @override public void oncompletion(mediaplayer mp) {     // todo auto-generated method stub    } } 

does have exception handling? because i'm bad @ that.

manifext.xml >

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.gamerspitch.easybluetooth" android:anydensity="false" android:versioncode="1" android:versionname="1.0" >  <uses-sdk     android:minsdkversion="8"     android:targetsdkversion="17" />  <uses-permission android:name="android.permission.bluetooth_admin" /> <uses-permission android:name="android.permission.bluetooth" />  <application     android:allowbackup="true"     android:icon="@drawable/icon"     android:label="@string/app_name"     android:theme="@style/apptheme" >     <activity         android:name="com.gamerspitch.easybluetooth.splashscreen"         android:label="@string/title_activity_splash_screen"          android:screenorientation="portrait">         <intent-filter>             <action android:name="android.intent.action.main" />              <category android:name="android.intent.category.launcher" />         </intent-filter>     </activity>      <activity         android:name="com.gamerspitch.easybluetooth.blueactivity"         android:label="@string/app_name"         android:screenorientation="portrait" >         <intent-filter>             <action android:name="android.intent.action.view" />              <category android:name="android.intent.category.default" />         </intent-filter>     </activity>  </application>  </manifest> 

the logcat >

`08-08 16:03:33.112: e/sensormanager(4428): exception dispatching input event.  08-08 16:03:33.112: e/androidruntime(4428): fatal exception: main  08-08 16:03:33.112: e/androidruntime(4428): java.lang.nullpointerexception  08-08 16:03:33.112: e/androidruntime(4428):    @    com.gamerspitch.easybluetooth.blueactivity.onsensorchanged(blueactivity.java:163)  08-08 16:03:33.112: e/androidruntime(4428):    @ android.hardware.legacysensormanager$legacylistener.onsensorchanged(legacysensormanager.jav a:274)  08-08 16:03:33.112: e/androidruntime(4428):    @ android.hardware.systemsensormanager$sensoreventqueue.dispatchsensorevent(systemsensormanager.java:371)  08-08 16:03:33.112: e/androidruntime(4428):    @ android.os.messagequeue.nativepollonce(native method)  08-08 16:03:33.112: e/androidruntime(4428):    @ android.os.messagequeue.next(messagequeue.java:132)  08-08 16:03:33.112: e/androidruntime(4428):    @ android.os.looper.loop(looper.java:124)  08-08 16:03:33.112: e/androidruntime(4428):    @ android.app.activitythread.main(activitythread.java:5103)  08-08 16:03:33.112: e/androidruntime(4428):    @ java.lang.reflect.method.invokenative(native method)  08-08 16:03:33.112: e/androidruntime(4428):    @ java.lang.reflect.method.invoke(method.java:525)  08-08 16:03:33.112: e/androidruntime(4428):    @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:737)  08-08 16:03:33.112: e/androidruntime(4428):    @ com.android.internal.os.zygoteinit.main(zygoteinit.java:553)  08-08 16:03:33.112: e/androidruntime(4428):    @ dalvik.system.nativestart.main(native method) 

`

thank in advance.

it's hard null without knowing line 163, guess there has been issue while creating mediaplayer object here:

m = mediaplayer.create(this, r.raw.pop);     m.setoncompletionlistener(this); 

as documentation create states: mediaplayer object, or null if creation failed