Android STUDIO, replacing Fragments

I am trying to do a connect the dots kind of Navigation thing in ANDROID Studio 0.8
I created this from BlankActivity with Fragment.

Fragment_My has a button that on click should goto FRAG02
FRAG02 goes to FRAG03

//===============================================================================
MyActivity
//===============================================================================

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
import android.widget.Toast;


public class MyActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    //.add(R.id.container, new FRAG02())
                    .commit();
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.my, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_my, container, false);
            return rootView;
        }
    }

    public void btnClickGotoFrag02 (View view){
        Toast.makeText(getApplicationContext(), "-----   just clicked goto frag02 ----", Toast.LENGTH_LONG).show();


        //  this is where we chall change to a new Fragment

        FragmentManager FM  = getFragmentManager();
        FragmentTransaction FT = FM.beginTransaction();
        //Fragment newFrag02 = new FRAG02();
        FT.replace(R.id.container,  new FRAG02());
        FT.addToBackStack(null);

        FT.commit();

        //mListener = (FRAG02.OnFragmentInteractionListener) MyActivity;
        //mListener.onFragmentInteraction(null);
    }



    public void btnClickGotoFrag03 (View view){
        Toast.makeText(getApplicationContext(), "-----   just clicked goto frag03 ----", Toast.LENGTH_LONG).show();

        //  this is where we chall change to a new Fragment

        FragmentManager FM  = getFragmentManager();
        FragmentTransaction FT = FM.beginTransaction();
        //Fragment newFrag02 = new FRAG02();
        FT.replace(R.id.container,  new FRAG03());
        FT.addToBackStack(null);

        FT.commit();

        //mListener = (FRAG03.OnFragmentInteractionListener) MyActivity;
        //mListener.onFragmentInteraction(null);
    }


}



//===============================================================================
FRAG02
//===============================================================================

package com.techlatin.vyoumans.blankfrag31;

import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;



/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link FRAG02.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link FRAG02#newInstance} factory method to
 * create an instance of this fragment.
 *
 */
public class FRAG02 extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment FRAG02.
     */
    // TODO: Rename and change types and number of parameters
    public static FRAG02 newInstance(String param1, String param2) {
        FRAG02 fragment = new FRAG02();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }
    public FRAG02() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_frag02, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnFragmentInteractionListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        public void onFragmentInteraction(Uri uri);
    }

}





//===============================================================================
FRAG03
//===============================================================================

package com.techlatin.vyoumans.blankfrag31;

import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;



/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link FRAG03.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link FRAG03#newInstance} factory method to
 * create an instance of this fragment.
 *
 */
public class FRAG03 extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment FRAG03.
     */
    // TODO: Rename and change types and number of parameters
    public static FRAG03 newInstance(String param1, String param2) {
        FRAG03 fragment = new FRAG03();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }
    public FRAG03() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_frag03, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnFragmentInteractionListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        public void onFragmentInteraction(Uri uri);
    }

}




//===============================================================================
activity_my.xml
//===============================================================================
<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=".MyActivity"
    tools:ignore="MergeRootFrame" />


//===============================================================================
fragment_my.xml
//===============================================================================

<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"
    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=".MyActivity$PlaceholderFragment">

    <TextView
        android:text="@string/txtFrag01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/txtFrag0001" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Goto Frag 02"
        android:id="@+id/btnGotoFrag02"
        android:layout_centerVertical="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:onClick="btnClickGotoFrag02" />


</RelativeLayout>


//===============================================================================
fragment_FRAG02.xml
//===============================================================================

<FrameLayout 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="com.techlatin.vyoumans.blankfrag31.FRAG02">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/txtFrag02"
        android:id="@+id/FRAG00002" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="GOTO FRAG 03"
        android:id="@+id/btnGotoFRAG03"
        android:layout_gravity="left|center_vertical"
        android:onClick="btnClickGotoFrag03" />

</FrameLayout>




//===============================================================================
fragment_FRAG03.xml
//===============================================================================


<FrameLayout 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="com.techlatin.vyoumans.blankfrag31.FRAG02">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/txtFrag02"
        android:id="@+id/FRAG00002" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="GOTO FRAG 03"
        android:id="@+id/btnGotoFRAG03"
        android:layout_gravity="left|center_vertical"
        android:onClick="btnClickGotoFrag03" />

</FrameLayout>