Урок 4: Справочник рыбака

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import androidx.core.view.GravityCompat;
import androidx.appcompat.app.ActionBarDrawerToggle;
import android.view.MenuItem;
import com.google.android.material.navigation.NavigationView;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.view.Menu;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Arrays;

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
private ListView list;
private String[] array;
private ArrayAdapter adapter;
private Toolbar toolbar;
private int category_index;

@Override
 protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
list = findViewById(R.id.listView);
array = getResources().getStringArray(R.array.fish_array);
adapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,new ArrayList(Arrays.asList(array)));
list.setAdapter(adapter);
toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

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();
navigationView.setNavigationItemSelectedListener(this);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
 public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
Intent intent = new Intent(MainActivity.this,Text_Content_Activity.class);
intent.putExtra("category",category_index);
intent.putExtra("position",position);
startActivity(intent);

}
});

}

@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);
toolbar.setTitle(R.string.fish);
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);
}

@Override
 public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
 int id = item.getItemId();

if (id == R.id.id_fish) {

fillArray(R.string.fish,R.array.fish_array,0 );

}
else if
 (id == R.id.id_na)
{

fillArray(R.string.na,R.array.na_array,1 );
}
else if (id == R.id.id_sna)
{
toolbar.setTitle(R.string.sna);
array = getResources().getStringArray(R.array.sna_array);
adapter.clear();
adapter.addAll(array);
adapter.notifyDataSetChanged();
category_index = 2;
}
else if (id == R.id.id_pri)
{
toolbar.setTitle(R.string.pri);
array = getResources().getStringArray(R.array.pri_array);
adapter.clear();
adapter.addAll(array);
adapter.notifyDataSetChanged();
category_index = 3;
}
else if (id == R.id.id_history)
{
toolbar.setTitle(R.string.history);
array = getResources().getStringArray(R.array.history_array);
adapter.clear();
adapter.addAll(array);
adapter.notifyDataSetChanged();
category_index = 4;
}
else if (id == R.id.id_advice)
{
toolbar.setTitle(R.string.advice);
array = getResources().getStringArray(R.array.advice_array);
adapter.clear();
adapter.addAll(array);
adapter.notifyDataSetChanged();
category_index = 5;
}

DrawerLayout drawer = findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
private void fillArray(int title,int arrayList,int index )
{
toolbar.setTitle(title);
array = getResources().getStringArray(arrayList);
adapter.clear();
adapter.addAll(array);
adapter.notifyDataSetChanged();
category_index = index;
}
}