android - Navigation drawer default fragment -

i novice developer , i´m integrating navigation drawer in app android-support v7 , have 1 question. when start app main layout this:

<?xml version="1.0" encoding="utf-8"?> 

<!-- main content view -->  <framelayout     android:id="@+id/content_frame"     android:layout_width="match_parent"     android:layout_height="match_parent" />  <!-- navigation drawer -->  <listview     android:id="@+id/left_drawer"     android:layout_width="240dp"     android:layout_height="match_parent"     android:layout_gravity="start"     android:background="@android:color/white"     android:choicemode="singlechoice"     android:divider="@android:color/transparent"     android:dividerheight="0dp" /> 

and main activity:

drawerlist.setonitemclicklistener(new onitemclicklistener() {         @override         public void onitemclick(adapterview<?> parent, view view,                 int position, long id) {              fragment fragment = null;              switch (position) {                 case 0:                     fragment = new fragment1();                     break;                 case 1:                     fragment = new fragment2();                     break;                 case 2:                     fragment = new fragment3();                     break;                   case 3:                     fragment = new fragment4();                     break;             }              fragmentmanager fragmentmanager =                      getsupportfragmentmanager();              fragmentmanager.begintransaction()                     .replace(r.id.content_frame, fragment)                     .commit();              drawerlist.setitemchecked(position, true);              tituloseccion = opcionesmenu[position];             getsupportactionbar().settitle(tituloseccion);              drawerlayout.closedrawer(drawerlist);         }     }); 

how can set default fragment main layout of app? thank you

if ok load default fragment every time activity created, can put fragmenttransaction in oncreate()

looks this:

@override public void oncreate(bundle savedinstancestate){      super.oncreate(savedinstancestate);     fragmenttransaction tx = getsupportfragmentmanager().begintransaction();     tx.replace(r.id.content_frame, new fragment1());     tx.commit();   } 

if want more sophisticated way of doing (for example switching different fragment when go main activity), can use intent extras determining fragment in oncreate(), put default fragment in defaultvalue upon loading extra:

int position = getintent().getintextra("position", 1); switch(position){      ...  }