Mercury-IM/app/src/main/java/org/mercury_im/messenger/ui/MainActivity.java

package org.mercury_im.messenger.ui;

import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import com.google.android.material.floatingactionbutton.FloatingActionButton;

import org.mercury_im.messenger.MercuryImApplication;
import org.mercury_im.messenger.R;
import org.mercury_im.messenger.ui.login.AccountsActivity;
import org.mercury_im.messenger.ui.login.LoginActivity;
import org.mercury_im.messenger.ui.settings.SettingsActivity;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        MercuryImApplication.getApplication().getAppComponent().inject(this);

        FloatingActionButton fab = findViewById(R.id.fab);
    }

    @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) {
        int id = item.getItemId();

        switch (id) {
            case R.id.action_settings:
                startActivity(new Intent(getApplicationContext(), SettingsActivity.class));
                return true;

            case R.id.action_login:
                startActivity(new Intent(getApplicationContext(), LoginActivity.class));
                return true;

            case R.id.action_accounts:
                startActivity(new Intent(getApplicationContext(), AccountsActivity.class));
                return true;
        }

        return super.onOptionsItemSelected(item);
    }
}