<Button
    android:id="@+id/button1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Fragment 1"
    android:onClick="selectFrag" />

 <Button
     android:id="@+id/button2"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:onClick="selectFrag"
     android:text="Fragment 2" />

<fragment
    android:name="xxxxxxxxxx.Fragment1"
    android:id="@+id/fragment_place"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  setContentView(R.layout.activity_main);
}

public void selectFrag(View view) {
     Fragment fr;

     if(view == findViewById(R.id.button2)) {
         fr = new Fragment2();

     }else {
         fr = new Fragment1();
     }

     FragmentManager fm = getFragmentManager();
     FragmentTransaction fragmentTransaction = fm.beginTransaction();
     fragmentTransaction.replace(R.id.fragment_place, fr);
     fragmentTransaction.commit();

 }