How can I let users remain logged in my android app

Question

package com.casser.casser;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.app.ProgressDialog;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.database.core.Tag;

import org.w3c.dom.Text;

public class Login extends AppCompatActivity {

    EditText email, password;
    Button login;
    TextView txt_signup;

    FirebaseAuth auth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        // This is ths screen optimization...
        try {
            this.getSupportActionBar().hide();
        } catch (NullPointerException e) {
        }

        View decorView = getWindow().getDecorView();
        int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                | View.SYSTEM_UI_FLAG_FULLSCREEN;
        decorView.setSystemUiVisibility(uiOptions);

        setContentView(R.layout.activity_login);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
    /*
        FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
        if (user != null) {
            // User is signed in
            Intent i = new Intent(Login.this, MainActivity.class);
            i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
            startActivity(i);
        } else {
            // User is signed out

        }
     */
        // This is ths screen optimization... After this the main login screen is there Work from below don't touch code above!

        email = findViewById(R.id.email);
        password = findViewById(R.id.password);
        login = findViewById(R.id.login);
        txt_signup = findViewById(R.id.txt_signup);


        auth = FirebaseAuth.getInstance();



        final SharedPreferences sp;
        sp = getSharedPreferences("login",MODE_PRIVATE);

        if(sp.getBoolean("logged",false)){
            goToMainActivity();
        }

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                goToMainActivity();
                sp.edit().putBoolean("logged",true).apply();
            }
        });

        txt_signup.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(Login.this, SignUp.class));

            }
        });
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final ProgressDialog pd = new ProgressDialog(Login.this);
                pd.setMessage("Please wait...");
                pd.show();

                String str_email = email.getText().toString();
                String str_password = password.getText().toString();

                if (TextUtils.isEmpty(str_email) || (TextUtils.isEmpty(str_password))) {
                    Toast.makeText(Login.this, "All fields are required", Toast.LENGTH_SHORT).show();
                } else {

                    auth.signInWithEmailAndPassword(str_email, str_password)
                            .addOnCompleteListener(Login.this, new OnCompleteListener<AuthResult>() {
                                @Override
                                public void onComplete(@NonNull Task<AuthResult> task) {
                                    if (task.isSuccessful()) {
                                        DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Users")
                                                .child(auth.getCurrentUser().getUid());

                                        reference.addValueEventListener(new ValueEventListener() {
                                            @Override
                                            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                                                pd.dismiss();
                                                Intent intent = new Intent(Login.this, MainActivity.class);
                                                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                                                startActivity(intent);
                                            }

                                            @Override
                                            public void onCancelled(@NonNull DatabaseError databaseError) {
                                                pd.dismiss();

                                            }
                                        });
                                    } else {
                                        pd.dismiss();
                                        Toast.makeText(Login.this, "SignIn failed", Toast.LENGTH_SHORT).show();
                                    }
                                }
                            });
                }

            }
        });


    }


    public void goToMainActivity() {
        Intent i = new Intent(this, MainActivity.class);
        startActivity(i);
    }

}

How Can I remain users logged in my app I have done auth with firebase how can I remain them logged in I have tried many things but they didn't work in same way like just once you logged in and then you don't need to sign in again until and unless you log out or delete your app I can also give some examples like facebook snapchat instagram AnyHelp will be very helpful I am beginning any help will be highly appreciated

Answer 1

package com.casser.casser;

import android.app.Application;
import android.content.Intent;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class  Home extends Application {

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

        FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
        FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();

        if (firebaseUser !=null){
            Intent i = new Intent(Home.this, MainActivity.class);

            i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            startActivity(i);
        }
    }
}

See create a class named anything you want I created named '.Home' create that and copy the above code and paste it there after that go into your manifest file and paste this : at the very top then you are done feel free to comment and contact in any case of problem thankyou Paste this at manifest file: android:name=".Home"