java - NullPointerException Error in android -

i working on media recorder application using android api 17. however, fatal exception:main , null pointer exception error during run time: i.e, while pressing record button unfortunately stopped working error. doing wrong?

here mainfest file:

<uses-sdk     android:minsdkversion="16"     android:targetsdkversion="18" /> <uses-permission android:name="android.permission.record_audio"/> <uses-permission android:name="android.permission.write_external_storage"/>  <application     android:allowbackup="true"     android:icon="@drawable/ic_launcher"     android:label="@string/app_name"     android:theme="@style/apptheme" >     <activity         android:name="co.example.projectplay.mainactivity"         android:label="@string/app_name" >         <intent-filter>             <action android:name="android.intent.action.main" />              <category android:name="android.intent.category.launcher" />         </intent-filter>     </activity> </application> 

this .java file

protected void oncreate(bundle savedinstancestate){      super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      file=environment.getexternalstoragestate()+"/temprecord.3gpp";      botn1=(button)findviewbyid(r.id.botn1);     botn1.setonclicklistener(new view.onclicklistener()      {          @override         public void onclick(view v)         {              play= mediaplayer.create(mainactivity.this,r.raw.a);             play.start();             play.setoncompletionlistener(new oncompletionlistener()             {                 public void oncompletion(mediaplayer play)                 {                     play.release();                 }             }             );         }     });       botn2=(button)findviewbyid(r.id.botn2);     botn2.setonclicklistener(new view.onclicklistener() {          @override         public void onclick(view v) {              play= mediaplayer.create(mainactivity.this,r.raw.b);             play.start();             play.setoncompletionlistener(new oncompletionlistener()             {                 public void oncompletion(mediaplayer play)                 {                     play.release();                 }             });         }     });     botn3=(button)findviewbyid(r.id.botn3);     botn3.setonclicklistener(new view.onclicklistener() {          @override         public void onclick(view v) {              play= mediaplayer.create(mainactivity.this,r.raw.c);             play.start();             play.setoncompletionlistener(new oncompletionlistener()             {                 public void oncompletion(mediaplayer play)                 {                     play.release();                 }             });         }     });      botnrecord=(button)findviewbyid(r.id.botnrecord);     botnrecord.setonclicklistener(new view.onclicklistener()      {         @override         public void onclick(view v)          {             if (botnrecord.gettext().tostring().equals("record"))              {                 try                  {                     startrecord();                 }                  catch (exception e)                   {                     e.printstacktrace();                 }                  txtbutton.settext("recording...");                 botnrecord.settext("end");              }             else if(botnrecord.gettext().tostring().equals("end"))              {                 stoprecord();                 txtbutton.settext("");                 botnrecord.settext("play");              }             else if(botnrecord.gettext().tostring().equals("play"))             {                 try {                     startplayback();                 }                  catch (exception e)                  {                      e.printstacktrace();                  }                 botnrecord.settext("stop");             }              else             {                 stopplayback();                 botnrecord.settext("record");             }         }        }); }    public void startrecord()throws exception {     if(record!=null)     {         //record.release();         record.reset();     }      file fileout=new file(file);      if(fileout!=null)     {         fileout.delete();     }     record=new mediarecorder();     record.setaudiosource(mediarecorder.audiosource.mic);     record.setoutputformat(mediarecorder.outputformat.three_gpp);     record.setaudioencoder(mediarecorder.audioencoder.amr_nb);     record.setoutputfile(file);     record.prepare();     record.start();  } public void stoprecord() {     record.stop();     record.release(); } public void startplayback()throws exception {     if(play!=null)     {         play.stop();         play.release();     }     play=new mediaplayer();     play.setdatasource(file);     play.prepare();     play.start();     play.setoncompletionlistener(new oncompletionlistener()     {         public void oncompletion(mediaplayer play)         {             play.release();         }     }     ); } public void stopplayback() {     play.stop();     play.release(); }  @override public boolean oncreateoptionsmenu(menu menu)  {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.main, menu);     return true; }  } 

this log cat error

• 03-11 05:13:04.803: e/androidruntime(814): fatal exception: main
• 03-11 05:13:04.803: e/androidruntime(814): java.lang.nullpointerexception
• 03-11 05:13:04.803: e/androidruntime(814): @ co.example.projectplay.mainactivity$4.onclick(mainactivity.java:106)
• 03-11 05:13:04.803: e/androidruntime(814): @ android.view.view.performclick(view.java:4204)
• 03-11 05:13:04.803: e/androidruntime(814): @ android.view.view$performclick.run(view.java:17355)
• 03-11 05:13:04.803: e/androidruntime(814): @ android.os.handler.handlecallback(handler.java:725)
• 03-11 05:13:04.803: e/androidruntime(814): @ android.os.handler.dispatchmessage(handler.java:92)
• 03-11 05:13:04.803: e/androidruntime(814): @ android.os.looper.loop(looper.java:137)
• 03-11 05:13:04.803: e/androidruntime(814): @ android.app.activitythread.main(activitythread.java:5041)
• 03-11 05:13:04.803: e/androidruntime(814): @ java.lang.reflect.method.invokenative(native method)
• 03-11 05:13:04.803: e/androidruntime(814): @ java.lang.reflect.method.invoke(method.java:511)
• 03-11 05:13:04.803: e/androidruntime(814): @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:793)
• 03-11 05:13:04.803: e/androidruntime(814): @ com.androi03-11 05:13:04.803: e/androidruntime(814): @ dalvik.system.nativestart.main(native method)d.internal.os.zygoteinit.main(zygoteinit.java:560)
• 03-11 05:13:04.803: e/androidruntime(814): @ dalvik.system.nativestart.main(native method)
• 03-11 05:13:08.062: i/process(814): sending signal. pid: 814 sig: 9

your code doesn't show assignment txtbutton. should this:

txtbutton=(textview)findviewbyid(r.id.txtbutton); 

before use first time.