Android: Can't replace fragments, getting a error on replace method

I am developing an app with navigation drawer and fragments but I can't seem to resolve one error.

I have a error in FragmentTransaction method replace(int,Fragment) . It is showing The method replace(int, Fragment) in the type FragmentTransaction is not applicable for the arguments (int, MyFragment).

MyFragment is a custom fragment.

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBarDrawerToggle;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
@SuppressWarnings("deprecation")
public class MainActivity extends ActionBarActivity implements OnItemClickListener {

    private DrawerLayout drawerlayout;
    private ListView listview;
    private String[] planets;
    private ActionBarDrawerToggle drawerlistener;
    private ActionBar actionBar;    
    private FragmentTransaction fragmenttransaction;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        drawerlayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        listview = (ListView) findViewById(R.id.list);
        planets = getResources().getStringArray(R.array.planets);
        listview.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        listview.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_activated_1, planets));
        listview.setOnItemClickListener(this);
        drawerlistener = new ActionBarDrawerToggle(this, drawerlayout, R.drawable.ic_drawer, R.string.drawer_open);

        drawerlayout.setDrawerListener(drawerlistener);
        actionBar = getSupportActionBar();
        actionBar.setHomeButtonEnabled(true);
        //getSupportActionBar().setDisplayShowHomeEnabled(true);
        actionBar.setDisplayHomeAsUpEnabled(true);

        FragmentManager fragmentmanager = getSupportFragmentManager();
        fragmenttransaction = fragmentmanager.beginTransaction();
        loadSelection(0);
    }

    private void loadSelection(int i) {
        // TODO Auto-generated method stub
        listview.setItemChecked(i, true);
        if(i==1)
        {
            MyFragment fragment1 = new MyFragment();
            fragmenttransaction.replace(R.id.main, fragment1);
            fragmenttransaction.commit();
        }
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onPostCreate(savedInstanceState);
        drawerlistener.syncState();
    }

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

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        // TODO Auto-generated method stub

        switch (position) {
        case 0:

            break;

        case 1:

            break;

        case 3:

            break;
        default:
            break;
        }
        drawerlayout.closeDrawer(listview);
    }
}

And the MyFragment.java is here:

package com.example.test3;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MyFragment extends Fragment
 {
   public MyFragment(){

    }
    @SuppressWarnings({ "deprecation" })
    @Override
    public void onAttach(Activity activity) {
        // TODO Auto-generated method stub
        super.onAttach(activity);
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        //return super.onCreateView(inflater, container, savedInstanceState);
        return inflater.inflate(R.layout.fragment1, container, false);
    }
    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onActivityCreated(savedInstanceState);
    }
    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
    }
}