Check if a perticular value exist in Firebase Database

Question

I'm developing an android application using java and Firebase. This is my code for creating a user profile and store the data in firebase database.

package com.eNotification.getnotify;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.content.ContentResolver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.ConnectivityManager;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.text.TextUtils;
import android.view.View;
import android.webkit.MimeTypeMap;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import com.eNotification.getnotify.utils.Utils;
import com.google.android.gms.tasks.Continuation;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.textfield.TextInputEditText;
import com.google.android.material.textfield.TextInputLayout;
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.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.StorageTask;
import com.google.firebase.storage.UploadTask;
import com.mikhaellopez.circularimageview.CircularImageView;
import com.squareup.picasso.Picasso;
import com.theartofdev.edmodo.cropper.CropImage;
import com.theartofdev.edmodo.cropper.CropImageView;

import java.util.ArrayList;
import java.util.List;

public class MainActivityCreateProfile extends AppCompatActivity {

    private static final int STORAGE_PERMISSION_CODE=1;

    private TextInputLayout dUsername,dRegNo;
    private TextInputEditText dEditUsername,dEditRegNo;
    private CircularImageView dProfileImage;
    private Spinner dCourse;
    private TextView selected;
    private Button dDoneBtn;

    private String uid,email;
    private String select="Select course",maxid,s;
    private Uri selectedImage=null,uri;

    private FirebaseDatabase firebaseDatabase;
    private DatabaseReference databaseReference;
    private StorageReference storageReference;
    private FirebaseStorage firebaseStorage;

    private StorageTask mUploadTask;

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

        firebaseDatabase = FirebaseDatabase.getInstance();
        firebaseStorage = FirebaseStorage.getInstance();
        databaseReference = FirebaseDatabase.getInstance().getReference().child("USERS");
        storageReference = firebaseStorage.getReference("Profile images");

        uid = getIntent().getStringExtra("uid");
        email = getIntent().getStringExtra("email");

        dProfileImage = findViewById(R.id.dProfileImg);
        dUsername = findViewById(R.id.dUsername);
        dRegNo = findViewById(R.id.dRegNo);
        dEditUsername = findViewById(R.id.dEditUsername);
        dEditRegNo = findViewById(R.id.dEditReg);
        selected = findViewById(R.id.course);
        dCourse = findViewById(R.id.dCourse);

        List<String> categories = new ArrayList<>();
        categories.add(0,"Select course");
        categories.add("BCA");
        categories.add("BBA");
        categories.add("BCOM");
        categories.add("BA");

        ArrayAdapter<String> dataAdapter;
        dataAdapter = new  ArrayAdapter(this,android.R.layout.simple_spinner_item,categories);

        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        dCourse.setAdapter(dataAdapter);
        dCourse.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            //    if (parent.getItemAtPosition(position).equals("Select course")){
              //      Toast.makeText(MainActivityCreateProfile.this, "Select the course", Toast.LENGTH_SHORT).show();
                //} else {
                    selected.setText(parent.getSelectedItem().toString());
                //}
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {
                Toast.makeText(MainActivityCreateProfile.this, "Select a course", Toast.LENGTH_SHORT).show();
            }
        });

        dDoneBtn = findViewById(R.id.dDoneBtn);

        dDoneBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                inputValidation();
            }
        });

        dProfileImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(MainActivityCreateProfile.this,
                        Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(MainActivityCreateProfile.this, "You have already granted permission", Toast.LENGTH_SHORT).show();
                    SelectImage();
                }  else {
                    requestStoragePermission();
                }
            }
        });
    }

    private void requestStoragePermission() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivityCreateProfile.this, Manifest.permission.READ_EXTERNAL_STORAGE)) {
            new AlertDialog.Builder(this)
                    .setTitle("Permission needed")
                    .setMessage("This Permission is needed for uploading the Image")
                    .setPositiveButton("ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            ActivityCompat.requestPermissions(MainActivityCreateProfile.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
                        }
                    })
                    .setNegativeButton("cancel", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss();
                        }
                    })
                    .create().show();
        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == STORAGE_PERMISSION_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permission granted", Toast.LENGTH_SHORT).show();
                SelectImage();
            } else {
                Toast.makeText(this, "Permission denied", Toast.LENGTH_SHORT).show();

            }
        }
    }

    public void SelectImage() {
        CropImage.activity()
                .setGuidelines(CropImageView.Guidelines.ON)
                .setAspectRatio(1,1)
                .start(this);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == CropImage.CROP_IMAGE_ACTIVITY_REQUEST_CODE) {
            CropImage.ActivityResult result = CropImage.getActivityResult(data);
            if (resultCode == RESULT_OK) {
                selectedImage = result.getUri();
                Picasso.get().load(selectedImage).into(dProfileImage);
            } else if (resultCode == CropImage.CROP_IMAGE_ACTIVITY_RESULT_ERROR_CODE) {
                Exception error = result.getError();
            }
        }
    }

    private void inputValidation() {
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        if (cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isConnected()) {
            //Username validation
            if (!Utils.inputValidation(dEditUsername)) {
                Toast.makeText(this, "Enter the username", Toast.LENGTH_SHORT).show();
                return;
            } else if (!Utils.usernameVerify(dEditUsername)) {
                Toast.makeText(this, "A Username should not exceed 15 characters", Toast.LENGTH_SHORT).show();
                return;
            } else {
                dUsername.setErrorEnabled(false);
            }

            //Reg no Validation
            if (!Utils.inputValidation(dEditRegNo)) {
                Toast.makeText(this, "Enter the Register No", Toast.LENGTH_SHORT).show();
                return;
            } else if (!Utils.regNoVerify(dEditRegNo)) {
                Toast.makeText(this, "Enter correct Register No", Toast.LENGTH_SHORT).show();
                return;
            }
            createProfile();
        }else {
            Toast.makeText(this, "Check internet connection", Toast.LENGTH_SHORT).show();
        }
    }

    public String GetFileExtension(Uri uri) {

        ContentResolver contentResolver = getContentResolver();
        MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
        return mimeTypeMap.getExtensionFromMimeType(contentResolver.getType(uri)) ;

    }

    private void createProfile(){
        final String username = dEditUsername.getText().toString();
        final String regNo = dEditRegNo.getText().toString();
        final String course = dCourse.getSelectedItem().toString();
        maxid = databaseReference.push().getKey();

        if (!TextUtils.isEmpty(username) && (!TextUtils.isEmpty(regNo))) {
            if (!course.equals(select)) {
                databaseReference.orderByChild("regNo").equalTo(regNo).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                            if (dataSnapshot.exists()){
                                Toast.makeText(MainActivityCreateProfile.this, "Reg no. exist", Toast.LENGTH_SHORT).show();
                            } else {
                                s = "https://firebasestorage.googleapis.com/v0/b/getnotify-da5c1.appspot.com/o/Permanent%2Fuser.png?alt=media&token=017d9013-ede2-49c7-b53b-6e96d90e3398";
                                UserDetails userDetails = new UserDetails(s, username, regNo, course, email);
                                databaseReference.child(maxid).setValue(userDetails);
                                Toast.makeText(MainActivityCreateProfile.this, "Upload Successful", Toast.LENGTH_SHORT).show();
                            }
                        }


                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {
                        Toast.makeText(MainActivityCreateProfile.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });
            } else {
                Toast.makeText(this, "Select a course", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(this, "Enter username and Register No.", Toast.LENGTH_SHORT).show();
        }
    }
}

I'm facing a problem where i want to check whether the Register No. already exist in the database or not and this is code to check that.

databaseReference.orderByChild("regNo").equalTo(regNo).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                            if (dataSnapshot.exists()){
                                Toast.makeText(MainActivityCreateProfile.this, "Reg no. exist", Toast.LENGTH_SHORT).show();
                            } else {
                                s = "https://firebasestorage.googleapis.com/v0/b/getnotify-da5c1.appspot.com/o/Permanent%2Fuser.png?alt=media&token=017d9013-ede2-49c7-b53b-6e96d90e3398";
                                UserDetails userDetails = new UserDetails(s, username, regNo, course, email);
                                databaseReference.child(maxid).setValue(userDetails);
                                Toast.makeText(MainActivityCreateProfile.this, "Upload Successful", Toast.LENGTH_SHORT).show();
                            }
                        }


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

The code works correctly. It detects if the value exist in database and shows Toast message Reg No. exist. If the value does not exist it successfully creates the child in database but it also displays Toast message Reg No. exist instead of Upload successful. I'm new to these concept so if you know anything please help.

Database node

Try `get` on `DocumentReference` instead of `addValueEventListener` — Hussain, Apr 18 '20 at 06:31

Ashish · Accepted Answer · 2020-04-18T07:09:17.117

2

As per Hussain Answer. addValueEventListener() is called each time there is changes in Your Database to overcome this situation you can call addListenerForSingleValueEvent(). Which will called once.

Other than that there is no Get option in Realtime Database

databaseReference.orderByChild("regNo").equalTo(regNo)
    .addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {
                //Do what you want to try
            }else{
                //Create New Node in Database
            }
        }

        @Override
            public void onCancelled(DatabaseError databaseError) {

        }
    });

edited Apr 18 '20 at 07:09

answered Apr 18 '20 at 07:04

Ashish

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Please tell me how to add .whereEqualTo – Dhanush Ambig Apr 18 '20 at 07:06
@Ashsh You said to add databaseReference.whereEqualTo. I'm not able to use it. Android studio showing error on .whereEqualTo – Dhanush Ambig Apr 18 '20 at 07:10
@DhanushAmbig I mistakenly provided you firestore query. Because i am not using ide right now. – Ashish Apr 18 '20 at 07:11

Hussain · Answer 2 · 2020-04-18T07:16:35.363

Here is what might be going wrong with the code. You are trying to check if the regno exist with addValueEventListener on user databaseReference.

From Android Documentation addValueEventListener does this

Add a listener for changes in the data at this location. Each time time the data changes, your listener will be called with an immutable snapshot of the data.

Therefore, when the dataSnapshot does not exists it creates a new node and eventually addValueEventListener fires again and your toast prints Reg no. exist.

What you can do is

databaseReference
    .child(regNo)
    .addListenerForSingleValueEvent(new ValueEventListenerAdapter() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            if (snapshot.exists()) {
               // Document exists
            } else {
               // Do something
            }
        }
    });

.whereEqualTo not working. How to add it. – Dhanush Ambig Apr 18 '20 at 07:04 — Dhanush Ambig, Apr 18 '20 at 07:04

Check if a perticular value exist in Firebase Database

2 Answers2