Firebase/Android - Check if data from database matches with another data in the same database

Question

I have an app that offers odd jobs to people. There is a section where one can see the jobs available to him near him. When the user clicks this option, jobs available in his location should show up. I have a firebase database with two nodes, Job and Users in which the user's location and job's location are added. How do I display jobs available in his location? For example, the user lives in Dubai, and he wants to see the jobs available in Dubai. I want to be able to extract the current user's location and check if it matches with the location of the job. This is what I have tried but it doesn't work.

Home_NearYou.java:

package com.example.oddsynew;

import android.os.Bundle;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

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.Query;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;

public class Home_NearYou extends AppCompatActivity {

    DatabaseReference myRef;
    FirebaseAuth mAuth;
    RecyclerView nearYouList;
    ArrayList<Job> list;
    HomeAdapter adapter;
    Query query;
    Users user;
    FirebaseUser u;
    String userID;

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

        try {
            mAuth = FirebaseAuth.getInstance();
            u = mAuth.getCurrentUser();
            userID = u.getUid();
            myRef = FirebaseDatabase.getInstance().getReference("Users").child(userID).child("state");

            nearYouList = (RecyclerView) findViewById(R.id.nearYou);
            nearYouList.setLayoutManager(new LinearLayoutManager(this));
            list = new ArrayList<Job>();

            adapter = new HomeAdapter(Home_NearYou.this, list);
            nearYouList.setAdapter(adapter);

            query = FirebaseDatabase.getInstance().getReference("Jobs")
                    .orderByChild("location")
                    .equalTo(myRef.toString());

            query.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    for (DataSnapshot ds : dataSnapshot.getChildren()) {
                        Job j = ds.getValue(Job.class);
                        list.add(j);
                    }
                    adapter.notifyDataSetChanged();
                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
                    Toast.makeText(Home_NearYou.this, "Error", Toast.LENGTH_SHORT).show();
                }
            });
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

Job.java:

package com.example.oddsynew;

public class Job {
    String job_name, recruiter_name, location, job_charge, add_pref, start_date, end_date, start_time, end_time, tasks, job_desc, prof_pic, job_tasks;

    public Job() {
    }

    public Job(String job_name, String recruiter_name, String location, String job_charge, String add_pref, String start_date,
               String end_date, String start_time, String end_time, String tasks, String job_desc, String prof_pic, String job_tasks) {
        this.job_name = job_name;
        this.recruiter_name = recruiter_name;
        this.location = location;
        this.job_charge = job_charge;
        this.add_pref = add_pref;
        this.start_date = start_date;
        this.end_date = end_date;
        this.start_time = start_time;
        this.end_time = end_time;
        this.tasks = tasks;
        this.job_desc = job_desc;
        this.prof_pic = prof_pic;
        this.job_tasks = job_tasks;
    }

    public Job(String prof_pic) {
        this.prof_pic = prof_pic;
    }

    public String getJob_name() {
        return job_name;
    }

    public void setJob_name(String job_name) {
        this.job_name = job_name;
    }

    public String getRecruiter_name() {
        return recruiter_name;
    }

    public void setRecruiter_name(String recruiter_name) {
        this.recruiter_name = recruiter_name;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

    public String getJob_charge() {
        return job_charge;
    }

    public void setJob_charge(String job_charge) {
        this.job_charge = job_charge;
    }

    public String getProf_pic() {
        return prof_pic;
    }

    public void setProf_pic(String prof_pic) {
        this.prof_pic = prof_pic;
    }

    public String getAdd_pref() {
        return add_pref;
    }

    public void setAdd_pref(String add_pref) {
        this.add_pref = add_pref;
    }

    public String getStart_time() {
        return start_time;
    }

    public void setStart_time(String start_time) {
        this.start_time = start_time;
    }

    public String getEnd_time() {
        return end_time;
    }

    public String getStart_date() {
        return start_date;
    }

    public void setStart_date(String start_date) {
        this.start_date = start_date;
    }

    public String getEnd_date() {
        return end_date;
    }

    public void setEnd_date(String end_date) {
        this.end_date = end_date;
    }

    public void setEnd_time(String end_time) {
        this.end_time = end_time;
    }

    public String getTasks() {
        return tasks;
    }

    public void setTasks(String tasks) {
        this.tasks = tasks;
    }

    public String getJob_desc() {
        return job_desc;
    }

    public void setJob_desc(String job_desc) {
        this.job_desc = job_desc;
    }

    public String getJob_tasks() {
        return job_tasks;
    }

    public void setJob_tasks(String job_tasks) {
        this.job_tasks = job_tasks;
    }
}

Users.java:

package com.example.oddsynew;

public class Users {
    private String fname;
    private String lname;
    private String email;
    private String pass;
    private String state;
    private String city;
    private String age;

    public Users() {
    }

    public String getFname() {
        return fname;
    }

    public String getLname() {
        return lname;
    }

    public String getEmail() {
        return email;
    }

    public String getPass() {
        return pass;
    }

    public void setFname(String fname) {
        this.fname = fname;
    }

    public void setLname(String lname) {
        this.lname = lname;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public void setPass(String pass) {
        this.pass = pass;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
}

Job Database:

User Database:

UPDATE: This is an example of how I insert data into Firebase.

SignUp2.java:

package com.example.oddsynew;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

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

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.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class SignUp2 extends AppCompatActivity {
    EditText state, city, age;
    Button submitBtn;
    FirebaseAuth mAuth;
    DatabaseReference myRef;
    Users user;
    String firstName, lastName, _email, _pass, state_, city_, age_;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sign_up2);

        state = (EditText) findViewById(R.id.state);
        city = (EditText) findViewById(R.id.city);
        age = (EditText) findViewById(R.id.age);
        submitBtn = (Button) findViewById(R.id.submitBtn);
        user = new Users();

        myRef = FirebaseDatabase.getInstance().getReference().child("Users");
        mAuth = FirebaseAuth.getInstance();

        /*if(mAuth.getCurrentUser() != null){
            startActivity(new Intent(getApplicationContext(), Home.class));
            Toast.makeText(SignUp2.this, "Welcome Back",Toast.LENGTH_LONG).show();
            finish();
        }*/

        submitBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                firstName = getIntent().getStringExtra("fName");
                lastName = getIntent().getStringExtra("lName");
                _email = getIntent().getStringExtra("email");
                _pass = getIntent().getStringExtra("pass");

                state_ = state.getText().toString().trim();
                city_ = city.getText().toString().trim();
                age_ = age.getText().toString();

                user.setFname(firstName);
                user.setLname(lastName);
                user.setEmail(_email);
                user.setPass(_pass);
                user.setState(state_);
                user.setCity(city_);
                user.setAge(age_);

                if(state_.matches("") || city_.matches("") || age_.matches("")){
                    Toast.makeText(SignUp2.this, "Please fill all fields",Toast.LENGTH_LONG).show();
                }
                else{
                    myRef.push().setValue(user);
                    Toast.makeText(SignUp2.this, "Data Inserted",Toast.LENGTH_LONG).show();
                }

                mAuth.createUserWithEmailAndPassword(_email, _pass).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if(task.isSuccessful()){
                            Toast.makeText(SignUp2.this, "User Created",Toast.LENGTH_LONG).show();
                            startActivity(new Intent(getApplicationContext(), Home.class));
                        }else{
                            Toast.makeText(SignUp2.this, "Error",Toast.LENGTH_LONG).show();

                        }
                    }
                });
            }
        });

    }
}

Answer 1

In your Users node you are not using the userID, those ids in the picture are ids generated by the push() method. Therefore first change the structure to use userID instead of push(), then you can do this:

mAuth = FirebaseAuth.getInstance();
u = mAuth.getCurrentUser();
userID = u.getUid();
myRef = FirebaseDatabase.getInstance().getReference("Users").child(userID);

            myRef.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                   String state = dataSnapshot.child("state").getValue(String.class);
                   query = FirebaseDatabase.getInstance().getReference("Jobs")
                    .orderByChild("location")
                    .equalTo(state);

                   query.addValueEventListener(new ValueEventListener() {
                    @Override
                   public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                     if(dataSnapshot.exists()){
                         //do whatever you want
                      }
                    }
                    @Override
                  public void onCancelled(@NonNull DatabaseError databaseError) {
                    Toast.makeText(Home_NearYou.this, "Error", Toast.LENGTH_SHORT).show();
                     }
                  });

                }
                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
                    Toast.makeText(Home_NearYou.this, "Error", Toast.LENGTH_SHORT).show();
                }
            });

So first retrieve the state from the user node. The only way to retrieve data is to use addValueEventListener. After retrieving the state, perform a different query for the jobs node that checks if the location is equal to the state retrieved, attach a valueEventListener and use the method exists() to check if you get any data from that query.