//========================================
    // Router
//  something is wrong here...  with .replace
    public void btnNextGotoStep00(View view){
        //setContentView(R.layout.fragment_zzf__v01__s00);
        getFragmentManager()
                .beginTransaction()
                .addToBackStack(null).
                replace("container", "fragment_zzf__v01__s00")
                .commit();
    }
    public void btnClickGotoStep01(View view){
        //setContentView(R.layout.fragment_zzf__v01__s01);
        getFragmentManager()
                .beginTransaction()
                .addToBackStack(null).
                replace("container", "fragment_zzf__v01__s01")
                .commit();
    }
    public void btnNextGotoStep02(View view){
        //setContentView(R.layout.fragment_zzf__v01__s02);
        getFragmentManager()
                .beginTransaction()
                .addToBackStack(null).
                replace("container", "fragment_zzf__v01__s02")
                .commit();
    }
    public void btnNextGotoStep03(View view){
        setContentView(R.layout.fragment_zzf__v01__s03);
    }
    public void btnNextGotoStep04(View view){
        setContentView(R.layout.fragment_zzf__v01__s04);
    }
    public void btnNextGotoStep05(View view){
        setContentView(R.layout.fragment_zzf__v01__s05);
    }
    public void btnNextGotoStep06(View view){
        setContentView(R.layout.fragment_zzf__v01__s06);
    }
    public void btnNextGotoStep10(View view){
        setContentView(R.layout.fragment_zzf__v01__s10);
    }
    public void btnNextGotoStep11(View view){
        setContentView(R.layout.fragment_zzf__v01__s11);
    }
    public void btnClose(View view){
        this.finish();
    }

This is the XML file for the Layout.
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.techlatin.logi.ZZF_V01_S00"
    tools:ignore="MergeRootFrame" />


///  It would seem to me that the FragmentID would be "container"?