how to set default fragment of naviagationdrawer on oncreate activity

Question

I tried a lot of fragment transaction ways but my default fragment is not launching while opening navigationdrawer activity.

     public class MainActivity extends AppCompatActivity{
    private DrawerLayout drawerLayout;
    private NavigationView navigationView;
    private int mSelectedId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        Toolbar toolbar = (Toolbar)findViewById(R.id.tool_bar);
        toolbar.setNavigationIcon(R.drawable.nav_icon);
        setSupportActionBar(toolbar);

        drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
        navigationView = (NavigationView)findViewById(R.id.nvView);
        setupDrawerContent(navigationView);

        mSelectedId = R.id.home;
        selectDrawerItem(mSelectedId);



    }


    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem.getItemId());
                        return true;
                    }
                });
    }
//    @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_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.
        switch (item.getItemId()) {
            case android.R.id.home:
                drawerLayout.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
    }

    public void selectDrawerItem(int mSelectedId) {
        // Create a new fragment and specify the planet to show based on
        // position
        Fragment fragment = null;

        Class fragmentClass;
        switch(mSelectedId) {
            case R.id.home:
                fragmentClass = Main.class;
                break;
            case R.id.orderhistory:
                fragmentClass = Order_history.class;
                break;
            case R.id.profile:
                fragmentClass = Profile.class;
                break;
            case R.id.contact:
                fragmentClass = Contact.class;
                break;
            case R.id.polices:
                fragmentClass = polices.class;
                break;
            default:
                fragmentClass = Main.class;
        }

        try {
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.flContent, fragment);
        fragmentTransaction.commit();

        // Highlight the selected item, update the title, and close the drawer
//        menuItem.setChecked(true);
//        setTitle(menuItem.getTitle());
        drawerLayout.closeDrawers();
    }
}

Its still showing the activity first while launching. do pass suggestions so as i can move forward.

Activity_main.xml

    <android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout"
    tools:context="in.co.blogspot.mellow.mellow.MainActivity">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <include
        android:id= "@+id/tool_bar"
        layout= "@layout/tool_bar"></include>

    <FrameLayout
        android:id="@+id/flContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />

</android.support.v4.widget.DrawerLayout>

Main.class

public class Main extends Fragment {
    public static TabLayout tabLayout;
    public static ViewPager viewPager;
    public static int int_items = 3 ;

    public Main() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main,null);
        tabLayout = (TabLayout) rootView.findViewById(R.id.tabs);
        viewPager = (ViewPager) rootView.findViewById(R.id.viewpager);

        /**
         *Set an Apater for the View Pager
         */
        viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));

        /**
         * Now , this is a workaround ,
         * The setupWithViewPager dose't works without the runnable .
         * Maybe a Support Library Bug .
         */

        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });

        // Inflate the layout for this fragment
        return rootView;
    }

    class MyAdapter extends FragmentPagerAdapter {

        public MyAdapter(FragmentManager fm) {
            super(fm);
        }

        /**
         * Return fragment with respect to Position .
         */

        @Override
        public Fragment getItem(int position)
        {
            switch (position){
                case 0 : return new p1();
                case 1 : return new p2();
                case 2 : return new p3();
            }
            return null;
        }

        @Override
        public int getCount() {

            return int_items;

        }

Answer 1

I think you can change a little your code.

Change your method selectDrawerItem in this way selectDrawerItem(int mSelectedId) so you can receive the id of the menu and not the menu so in onCreate() method you can do something like this

MainActivity

public class MainActivity extends AppCompatActivity {

    private DrawerLayout drawerLayout;
    private NavigationView navigationView;
    private int mSelectedId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
        navigationView = (NavigationView)findViewById(R.id.nvView);
        setupDrawerContent(navigationView);

        mSelectedId = R.id.orderhistory;
        selectDrawerItem(mSelectedId);

    }


    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem.getItemId());
                        return true;
                    }
                });
    }
//    @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_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.
        switch (item.getItemId()) {
            case android.R.id.home:
                drawerLayout.openDrawer(GravityCompat.START);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
    }

    public void selectDrawerItem(int mSelectedId) {
        // Create a new fragment and specify the planet to show based on
        // position
        Fragment fragment = null;

        Class fragmentClass;
        switch(mSelectedId) {
            case R.id.home:
                fragmentClass = Main.class;
                break;
            case R.id.orderhistory:
                fragmentClass = Order_history.class;
                break;
            default:
                fragmentClass = Main.class;
        }

        try {
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.flContent, fragment);
        fragmentTransaction.commit();

        // Highlight the selected item, update the title, and close the drawer
//        menuItem.setChecked(true);
//        setTitle(menuItem.getTitle());
        drawerLayout.closeDrawers();
    }
}

activity_main.xml

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/drawer_layout">

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

        <FrameLayout
            android:id="@+id/flContent"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:menu="@menu/drawer_view" />

</android.support.v4.widget.DrawerLayout>

drawer_view.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/home"
        android:title="Home"
        />

    <item
        android:id="@+id/orderhistory"
        android:title="Cursos"
        />
</menu>

Order_history.java

public class Order_history extends Fragment {


    public Order_history() {
        // Required empty public constructor
    }


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

}

fragment_order_history.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.enterprise.prueba.Order_history">

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

</FrameLayout>

Main.Java

public class Main extends Fragment {

    public Main() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, null);


        // Inflate the layout for this fragment
        return rootView;
    }
}

fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="I'm a fragment"/>

</LinearLayout>

Edited

It's very weird, now I create a new project with the same code and this is the result when I select order history in Oncreate().

I Update my code to show you all the files