Why findFragmentById returns the old fragment was in before the call to replace FragmentLayout?

Question

Why after changing fragments from the first(pageNews) to the second(pageViewFromWeb) "findFragmentById" returns a reference to the first(pageNews) fragment?

layout:

<RelativeLayout 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"
    tools:context=".MainActivity"
    android:paddingTop="10dp"
    android:background="#000">

    <FrameLayout
        android:id="@+id/frgmCont"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#000000">
    </FrameLayout>

</RelativeLayout>

code:

   fTrans = getSupportFragmentManager().beginTransaction();
   fTrans.add(R.id.frgmCont, pageNews);
   ....
   ....    
   public void selectNews(String news_id) {
   // Toast.makeText(this, news_id, Toast.LENGTH_SHORT).show();
    fTrans = getSupportFragmentManager().beginTransaction();
    fTrans.replace(R.id.frgmCont, pageViewFromWeb);
    fTrans.commit();
    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.frgmCont);
    ...
}

Answer 1

Its because replace() does not execute immediately, but the FragmentTransaction is scheduled. When you findFragmentById() immediately after replacing fragments, they are not replaced yet...