android - Fragment is not shown on Activity -

in app,one activity has include 3 fragments, 1 of them remains on activity other 2 have change places. fragments not shown on activity.

i have read somewhere here should change linearlayout fragmentlayout did not work.

public class mainactivity extends actionbaractivity {  private final fragment_1to6 f1to6 = new fragment_1to6(); private final fragment_7to12 f7to12 = new fragment_7to12();  private fragmentmanager mfragmentmanager; private framelayout mbuttonslayout, mlayout1to6; private framelayout mlayout7to12;  private static final int match_parent = linearlayout.layoutparams.match_parent; private static final int wrap_content = linearlayout.layoutparams.wrap_content;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);       mbuttonslayout = (framelayout) findviewbyid(r.id.fragment_buttons);     mlayout1to6 = (framelayout) findviewbyid(r.id.fragment_1to6);     mlayout7to12 = (framelayout) findviewbyid(r.id.fragment_7to12);      mfragmentmanager = getfragmentmanager();     final fragmenttransaction ft = mfragmentmanager.begintransaction();      ft.add(r.id.fragment_buttons, new buttonsfragment());     ft.add(r.id.fragment_1to6, f1to6);      ft.addtobackstack("fragment_buttons");     ft.addtobackstack("fragment_1to6");      ft.commit();      mfragmentmanager             .addonbackstackchangedlistener(new fragmentmanager.onbackstackchangedlistener() {                 public void onbackstackchanged() {                     setlayout();                 }             });       mfragmentmanager.executependingtransactions();   }  private void setlayout() {      // determine whether fragment has been added     if (!f7to12.isadded()) {          mbuttonslayout.setlayoutparams(new linearlayout.layoutparams(wrap_content,                 match_parent, 1f));         mlayout1to6.setlayoutparams(new linearlayout.layoutparams(wrap_content,                 match_parent, 6f));     } else {          mbuttonslayout.setlayoutparams(new linearlayout.layoutparams(wrap_content,                 match_parent, 1f));         // make titlelayout take 6/13 of layout's width         mlayout1to6.setlayoutparams(new linearlayout.layoutparams(wrap_content,                 match_parent, 6f));          // make quotelayout take 6/13's of layout's width         mlayout7to12.setlayoutparams(new linearlayout.layoutparams(wrap_content,                 match_parent, 6f));     }   } 

how can solve ?

i had tablerows , reason, deleted them , made linearlayout , shows in preview of fragment not in activity_main. xml code main activity. , below xlm code of fragment activity. , adding fragment activity calling:mbuttonsfragment = (buttonsfragment) mfragmentmanager.findfragmentbyid(r.id.fragment_buttons);

    <linearlayout     xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:paddingleft="@dimen/activity_horizontal_margin"     android:paddingright="@dimen/activity_horizontal_margin"     android:paddingtop="@dimen/activity_vertical_margin"     android:paddingbottom="@dimen/activity_vertical_margin"     tools:context=".mainactivity"     android:orientation="horizontal">       <include         android:id="@+id/app_bar"         layout="@layout/app_bar" />       <fragment         android:layout_width="wrap_content"         android:layout_height="match_parent"         android:id="@+id/fragment_buttons"         class="com.example.user.timeline.buttonsfragment"         tools:layout="@layout/fragment_buttons"         android:layout_weight="1"         android:layout_gravity="left">      </fragment>        <framelayout      android:layout_width="match_parent"     android:layout_height="match_parent"         class="com.example.user.timeline.fragment_1to6"     android:id="@+id/fragment_1to6"         tools:layout="@layout/fragment_buttons"         android:layout_weight="3"> </framelayout>       <framelayout     android:layout_width="match_parent"     android:layout_height="match_parent"     android:id="@+id/fragment_7to12"         android:layout_weight="3"> </framelayout>   </linearlayout>      <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="wrap_content"     android:layout_height="match_parent"     tools:context="com.example.user.timeline.buttonsfragment"     android:orientation="vertical"    >       <button             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:id="@+id/button"             android:text="add activity"             android:width="40dp"             android:height="30dp"             android:background="#b6b6b6"             android:textcolor="#000000"             android:onclick="onclick"               />          <button             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="add activity"             android:id="@+id/button2"             android:width="40dp"             android:height="30dp"             android:background="#b6b6b6"             android:textcolor="#000000"             android:onclick="onclick" />            <button             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="add activity"             android:id="@+id/button3"             android:layout_column="0"             android:width="40dp"             android:height="30dp"             android:background="#b6b6b6"             android:textcolor="#000000"             android:onclick="onclick" />  </linearlayout>