MainActivity.java

package com.servilat.intouch;

import android.os.Bundle;
import android.support.design.widget.NavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
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.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.servilat.intouch.dialog.DialogsListFragment;
import com.servilat.intouch.friends.FriendListFragment;
import com.servilat.intouch.login.LoginVkFragment;
import com.squareup.picasso.Picasso;
import com.vk.sdk.VKAccessToken;
import com.vk.sdk.VKSdk;
import com.vk.sdk.api.VKApi;
import com.vk.sdk.api.VKApiConst;
import com.vk.sdk.api.VKParameters;
import com.vk.sdk.api.VKRequest;
import com.vk.sdk.api.VKResponse;
import com.vk.sdk.api.model.VKApiUserFull;
import com.vk.sdk.api.model.VKList;

import org.json.JSONException;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {
    private DrawerLayout drawerLayout;
    private Fragment visibleFragment;

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        toolbar.setBackgroundColor(getResources().getColor(R.color.colorVk));
        drawerLayout = findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawerLayout, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close) {
            @Override
            public void onDrawerClosed(View drawerView) {
                super.onDrawerClosed(drawerView);
                if (visibleFragment != null) {
                    FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
                    fragmentTransaction.replace(R.id.frame_layout, visibleFragment, "visible_fragment");
                    fragmentTransaction.addToBackStack(null);
                    fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
                    fragmentTransaction.commit();
                }
            }
        };
        drawerLayout.addDrawerListener(toggle);
        toggle.syncState();

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

        if (!VKSdk.isLoggedIn()) {
            drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED);
            visibleFragment = new LoginVkFragment();
            FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
            fragmentTransaction.replace(R.id.frame_layout, visibleFragment, "visible_fragment");
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
            fragmentTransaction.commit();
        } else {
            showUserDialogs();
            vkRequestForHeader();
        }
    }
/*

    @Override
    protected void onStart() {
        super.onStart();

    }
*/

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

    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        int id = item.getItemId();

        visibleFragment = null;
        switch (id) {
            case R.id.nav_friends:
                showUserFriends();
                break;
            case R.id.nav_messages:
                showUserDialogs();
                break;
        }

        drawerLayout.closeDrawer(GravityCompat.START);
        return true;
    }

    private void showUserFriends() {
        FriendListFragment friendListFragment = new FriendListFragment();

        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.frame_layout, friendListFragment, "visible_friends");
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        fragmentTransaction.commit();
    }


    public void showUserDialogs() {
        DialogsListFragment dialogsListFragment = new DialogsListFragment();

        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.frame_layout, dialogsListFragment, "visible_dialogs");
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        fragmentTransaction.commit();
    }

    public void vkRequestForHeader() {
        VKRequest vkRequest = VKApi.users().get(VKParameters.from(
                VKApiConst.USER_IDS, VKAccessToken.currentToken().userId,
                VKApiConst.FIELDS, "photo_100, status"));

        vkRequest.executeWithListener(new VKRequest.VKRequestListener() {
            @Override
            public void onComplete(VKResponse response) {
                super.onComplete(response);
                VKApiUserFull currentVKUser = (VKApiUserFull) ((VKList) response.parsedModel).get(0);
                String status = "";
                try {
                    status = currentVKUser.fields.getString("status");
                } catch (JSONException ignored) {
                }
                fillNavigationDrawerHeader(currentVKUser.toString(), status, currentVKUser.photo_100);
            }
        });
    }

    private void fillNavigationDrawerHeader(String fullName, String status, String photo) {
        View header = ((NavigationView) findViewById(R.id.nav_view)).getHeaderView(0);
        ((TextView) header.findViewById(R.id.nav_user_name)).setText(fullName);
        ((TextView) header.findViewById(R.id.nav_user_status)).setText(status);
        Picasso.with(getApplicationContext())
                .load(photo)
                .placeholder(R.drawable.placeholder_person)
                .error(R.drawable.placeholder_person)
                .into((ImageView) header.findViewById(R.id.nav_user_photo));
    }
}