Mobile_Application_Development_project/DailyHelper/app/src/main/java/at/fhj/swd/dailyhelper/ui/activity/MainActivity.java

package at.fhj.swd.dailyhelper.ui.activity;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.support.v4.view.GravityCompat;
import android.support.v7.app.ActionBarDrawerToggle;
import android.view.MenuItem;
import android.support.design.widget.NavigationView;
import android.support.v4.widget.DrawerLayout;

import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;

import at.fhj.swd.dailyhelper.R;
import at.fhj.swd.dailyhelper.ui.fragemnt.HomeFragment;
import at.fhj.swd.dailyhelper.ui.fragemnt.LevelFragment;
import at.fhj.swd.dailyhelper.ui.fragemnt.MapFragment;
import at.fhj.swd.dailyhelper.ui.fragemnt.WeatherFragment;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {


    private static final String HOME = "home";
    private static final String WEATHER = "weather";
    private static final String MAP = "map";
    private static final String LEVEL = "level";


    private HomeFragment homeFragment;
    private LevelFragment levelFragment;
    private MapFragment mapFragment;
    private WeatherFragment weatherFragment;

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


        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        homeFragment = new HomeFragment();
        levelFragment = new LevelFragment();
        mapFragment = new MapFragment();
        weatherFragment = new WeatherFragment();

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
        DrawerLayout drawer = findViewById(R.id.drawer_layout);
        NavigationView navigationView = findViewById(R.id.nav_view);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.add(R.id.flFragmentContainer, homeFragment);
        transaction.add(R.id.flFragmentContainer, levelFragment);
        transaction.add(R.id.flFragmentContainer, mapFragment);
        transaction.add(R.id.flFragmentContainer, weatherFragment);

        transaction.commit();

        setSelectedFragment(HOME);

        navigationView.setNavigationItemSelectedListener(this);
    }

    @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 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();

        //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();

        if (id == R.id.nav_home) {
            setSelectedFragment(HOME);
        } else if (id == R.id.nav_weather) {
            setSelectedFragment(WEATHER);
        } else if (id == R.id.nav_map) {
            setSelectedFragment(MAP);
       // } else if (id == R.id.nav_level) {
      //      setSelectedFragment(LEVEL);
        }

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

    private void setSelectedFragment (String fragmentName) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();

        transaction.hide(homeFragment);
        transaction.hide(levelFragment);
        transaction.hide(mapFragment);
        transaction.hide(weatherFragment);
        System.out.println(fragmentName);
        switch (fragmentName) {
            case HOME:
                transaction.show(homeFragment);
                break;
            case LEVEL:
                 transaction.show(levelFragment);
                break;
            case MAP:
                transaction.show(mapFragment);
                break;
            case WEATHER:
                transaction.show(weatherFragment);
                break;
        }
        transaction.commit();
    }
}