problems to interact with the database from a fragment

From so much research I realized that the fragment do not work the relation with the database SQLite as do the activity directly, that this could help me to work or what is the correct code line for to be able to work with the Database from fragment

SQLite.class (where I have the database only 2 tables)

package company.viral.organizadorjec;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by erny on 27/10/2016.
 */

public class SQLite extends SQLiteOpenHelper {

    //constructor.......
    public SQLite(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }



    //aqui se crea la tabla...
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table usuarios (id_usuario integer primary key autoincrement, " +
                "usuario text, clave text)");


        db.execSQL("create table profesores (id_profesor integer primary key autoincrement," +
                "nombre_profesor text, comentario_profesor text");


        db.execSQL("insert into usuarios values('0','admin','admin')");


    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("create table usuarios (id_usuario integer primary key autoincrement, " +
                "usuario text, clave text)");


        db.execSQL("create table profesores (id_profesor integer primary key autoincrement," +
                "nombre_profesor text, comentario_profesor text");

        db.execSQL("insert into usuarios values('0','admin','admin')");


    }
}

MenuCentral (is the activity where the fragment works which is a Navigation Drawer )

    package company.viral.organizadorjec;

import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentManager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.PopupWindow;
import android.widget.RelativeLayout;

import company.viral.organizadorjec.Fragment.AjustesF;
import company.viral.organizadorjec.Fragment.CalendarioF;
import company.viral.organizadorjec.Fragment.ConfiguracionActividadF;
import company.viral.organizadorjec.Fragment.ConfiguracionMateriaF;
import company.viral.organizadorjec.Fragment.ConfiguracionPeriodoF;
import company.viral.organizadorjec.Fragment.ConfiguracionProfesorF;
import company.viral.organizadorjec.Fragment.InicioF;
import company.viral.organizadorjec.Fragment.PerfilF;
import company.viral.organizadorjec.Fragment.ProfesoresF;

public class MenuCentral extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    private PopupWindow popupadicion;
    private DrawerLayout posicionpopup;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu_central);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        posicionpopup = (DrawerLayout) findViewById(R.id.drawer_layout);



        //colocamos el fragment con que inicia el menu

        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.contenedor,new InicioF()).commit();


        //este es el apartado para el botonsito flotante

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {

            //metodo de escucha para el popup
            @Override
            public void onClick(View view) {

                //implementamos el popup
                LayoutInflater inflater = (LayoutInflater)getBaseContext().getSystemService(LAYOUT_INFLATER_SERVICE);
                final View vistaadicion = inflater.inflate(R.layout.activity_pop_adicion,null);

                popupadicion = new PopupWindow(
                        vistaadicion, RelativeLayout.LayoutParams.WRAP_CONTENT,
                        RelativeLayout.LayoutParams.WRAP_CONTENT
                );

                //luego de clicear y abrir el popup le decimos...
                //si das al profe ve a profe
                LinearLayout btnprofe = (LinearLayout) vistaadicion.findViewById(R.id.btnagregarprofesor);
                btnprofe.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        FragmentManager fragmentManager = getSupportFragmentManager();
                        fragmentManager.beginTransaction().replace(R.id.contenedor,new ConfiguracionProfesorF()).commit();
                        popupadicion.dismiss();

                    }
                });
                //si le das actividad ve actividad
                LinearLayout btnactividad = (LinearLayout) vistaadicion.findViewById(R.id.btnagregaractividad);
                btnactividad.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        FragmentManager fragmentManager = getSupportFragmentManager();
                        fragmentManager.beginTransaction().replace(R.id.contenedor,new ConfiguracionActividadF()).commit();
                        popupadicion.dismiss();

                    }
                });
                //si le das a materias ve a materias
                LinearLayout btnmaterias = (LinearLayout) vistaadicion.findViewById(R.id.btnagregarmateria);
                btnmaterias.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        FragmentManager fragmentManager = getSupportFragmentManager();
                        fragmentManager.beginTransaction().replace(R.id.contenedor,new ConfiguracionMateriaF()).commit();
                        popupadicion.dismiss();

                    }
                });
                //si le das a periodo ve a periodo
                LinearLayout btnperiodo = (LinearLayout) vistaadicion.findViewById(R.id.btnagregarperiodo);
                btnperiodo.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        FragmentManager fragmentManager = getSupportFragmentManager();
                        fragmentManager.beginTransaction().replace(R.id.contenedor,new ConfiguracionPeriodoF()).commit();
                        popupadicion.dismiss();

                    }
                });
                //luego le decimos que cierre el popup con el boton

                Button cerrarboton = (Button) vistaadicion.findViewById(R.id.btnpopupcerrar);
                cerrarboton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        popupadicion.dismiss();
                    }
                });
                //hubicamos donde queremos el popup
                popupadicion.showAtLocation(posicionpopup, Gravity.CENTER,0,0 );
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

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

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        FragmentManager fragmentManager = getSupportFragmentManager();

        if (id == R.id.nav_camera) {
            fragmentManager.beginTransaction().replace(R.id.contenedor,new InicioF()).commit();

        } else if (id == R.id.nav_gallery) {
            fragmentManager.beginTransaction().replace(R.id.contenedor,new ProfesoresF()).commit();

        } else if (id == R.id.nav_slideshow) {
            fragmentManager.beginTransaction().replace(R.id.contenedor,new CalendarioF()).commit();

        } else if (id == R.id.nav_manage) {
            fragmentManager.beginTransaction().replace(R.id.contenedor,new AjustesF()).commit();

        } else if (id == R.id.nav_share) {
            fragmentManager.beginTransaction().replace(R.id.contenedor,new PerfilF()).commit();

        } else if (id == R.id.nav_send) {

        } else if (id == R.id.nav_materia){
            fragmentManager.beginTransaction().replace(R.id.contenedor,new ConfiguracionMateriaF()).commit();
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

ProffesorF configuration ( fragment involved in the problem)

    package company.viral.organizadorjec.Fragment;

    import android.content.ContentValues;
    import android.database.sqlite.SQLiteDatabase;
    import android.os.Bundle;
    import android.support.v4.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.Button;
    import android.widget.EditText;

    import company.viral.organizadorjec.R;
    import company.viral.organizadorjec.SQLite;


    public class ConfiguracionProfesorF extends Fragment {

        private EditText etnombreprofesorf;
        private EditText etcomentarioprofesorf;
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            // Inflate the layout for this fragment
            View view = inflater.inflate(R.layout.fragment_configuracion_profesor, container, false);

            etnombreprofesorf = (EditText)view.findViewById(R.id.etnombreprofesor);
            etcomentarioprofesorf = (EditText)view.findViewById(R.id.etcomentarioprofesor);

            Button btnagrerarpf = (Button)view.findViewById(R.id.btnagregarprofesor);
            btnagrerarpf.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    String auxnp = etnombreprofesorf.getText().toString();
                    String auxcp = etcomentarioprofesorf.getText().toString();

                    SQLite admin = new SQLite(getActivity(),"administracion",null,1);
                    SQLiteDatabase bd = admin.getWritableDatabase();

                    ContentValues registroprofe = new ContentValues();

                    registroprofe.put("nombre_profesor",auxnp);
                    registroprofe.put("comentario_profesor",auxcp);

                    bd.insert("profesores",null,registroprofe);

                    bd.close();

                    etnombreprofesorf.setText("");
                    etcomentarioprofesorf.setText("");

                }
            });


            return view;
        }


    }

**fragment_configuracion_profesor** (correspondiente 'layout' de dicho 'fragment')

<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="company.viral.organizadorjec.Fragment.ConfiguracionProfesorF">


    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:text="Registro de Profesores"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:textSize="24sp"
            tools:textColor="@color/colorPrimary"/>

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1">

            <Space
                android:layout_width="match_parent"
                android:layout_height="20dp" />

            <EditText
                android:layout_height="wrap_content"
                android:inputType="textPersonName"
                android:ems="10"
                android:id="@+id/etnombreprofesor"
                android:hint="Nombre del profesor"
                android:layout_width="match_parent" />

            <TextView
                android:text="Elija primera caracteristica:"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/textView8" />

            <Spinner
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/spinner" />

            <Space
                android:layout_width="match_parent"
                android:layout_height="35dp" />

            <TextView
                android:text="Elija segunda caracteristica:"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/textView11" />

            <Spinner
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/spinner2" />

            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:inputType="textMultiLine"
                android:ems="10"
                android:hint="Si lo desea ingrese comentarios del profesor"
                android:id="@+id/etcomentarioprofesor" />


        </LinearLayout>

        <LinearLayout
            android:orientation="horizontal"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <Button
                android:text="Agregar"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/button2"
                android:layout_weight="1"
                style="@android:style/Widget.Button" />

            <Button
                android:text="Editar"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/button"
                android:layout_weight="1"
                style="@android:style/Widget.Button" />
        </LinearLayout>

    </LinearLayout>

</FrameLayout>

Thank you very much for helping me, sorry for the code so noob, but keep in mind that I'm starting and is "self-taught" if they have exercises to learn how to reduce code of truth I would really appreciate it ... finally many Thanks for your time !!!