How to connect code with the layout (.xml) after I selected it in a Navigation Drawer?

If I select something in the Navigation Drawer, it switches layouts but how do I bring code behind it?

I normally had different classes and opened them with Intent. So the code was always in the Classfor the specific layout. But now I wan't to navigate through a Navigation Drawer.

First.java: Thats how I navigate now, but how to connect the code from Second.java which is for secondlayout.xml?

private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
private String[] list = {"first","second","third"};


protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.navigation_drawer);
    mTitle = mDrawerTitle = getTitle();

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerList = (ListView) findViewById(R.id.left_drawer);

    mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
    mDrawerList.setAdapter(new ArrayAdapter<String>(this,R.layout.drawer_list_item, list));
    mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

    getActionBar().setDisplayHomeAsUpEnabled(true);
    getActionBar().setHomeButtonEnabled(true);

    mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout,
            R.drawable.ic_drawer,  
            R.string.drawer_open,  
            R.string.drawer_close 
    ) {
        public void onDrawerClosed(View view) {
            getActionBar().setTitle(mTitle);
            invalidateOptionsMenu();
        }

        public void onDrawerOpened(View drawerView) {
            getActionBar().setTitle(mDrawerTitle);
            invalidateOptionsMenu();
        }
    };
    mDrawerLayout.setDrawerListener(mDrawerToggle);

    if (savedInstanceState == null) {
        selectItem(0);
    }
}

private void selectItem(int position){
    FrameLayout frameLayout = (FrameLayout) findViewById(R.id.content_frame);
    LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    if(position == 0){
        RelativeLayout myView = (RelativeLayout) inflater.inflate(R.layout.firstlayout, null);
        frameLayout.addView(myView);
    }else if(position == 1){
        RelativeLayout myView = (RelativeLayout) inflater.inflate(R.layout.secondlayout, null);
        frameLayout.addView(myView);
    }else if(position == 2){
        RelativeLayout myView = (RelativeLayout) inflater.inflate(R.layout.thirdlayout, null);
        frameLayout.addView(myView);
    }
    mDrawerList.setItemChecked(position, true);
    setTitle(list[position]);
    mDrawerLayout.closeDrawer(mDrawerList);
}

    private class DrawerItemClickListener implements ListView.OnItemClickListener {
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        selectItem(position);
    }
}

public void setTitle(CharSequence title) {
    mTitle = title;
    getActionBar().setTitle(mTitle);
}

protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    mDrawerToggle.syncState();
}

public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    mDrawerToggle.onConfigurationChanged(newConfig);
}

public boolean onOptionsItemSelected(MenuItem item) {
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}