Firebase Cloud Firestore

3 min readFeb 7, 2023

Set Cloud Firestore

dependencies {
    // Import the BoM for the Firebase platform
    implementation platform('com.google.firebase:firebase-bom:31.2.0')

    // Declare the dependency for the Cloud Firestore library
    // When using the BoM, you don't specify versions in Firebase library dependencies
    implementation 'com.google.firebase:firebase-firestore-ktx'
}

Select a starting mode for your Cloud Firestore Security Rules: To get started with the Android SDK, select test mode. Good for getting started with mobile libraries, but allows anyone to read and overwrite your data. After testing, make sure to review the Secure your data section.

When you enable Cloud Firestore, it also enables the API in the Cloud API Manager.

Firestore user Entity Insert

java > models > User.kt class

data class User(
    val uid: String, 
    val displayName: String? = "",
    val imageUrl: String? = ""
)

java > daos> UserDao.kt class

Firebase.firestore and FirebaseFirestore.getInstance() are the same. They both return the same singleton instance of the FirebaseFirestore class, which provides the entry point for all server-side Firestore operations.

class UserDao {

    // Access a Cloud Firestore instance from your Activity

    private val db = FirebaseFirestore.getInstance()
    
    /* Or
    val db = Firebase.firestore*/

    private val userCollection = db.collection("users")

    fun allUser(user: User?){
        user?.let {
            // 
            GlobalScope.launch(Dispatchers.IO) {
                userCollection.document(user.uid).set(it)
            }
        }
    }
}

Add User Firebase (Activity)

private fun updateUI(firebaseUser: FirebaseUser?) {
    if(firebaseUser!=null) {

        /*Add User in Firebase*/
        val user = User(firebaseUser.uid, firebaseUser.displayName, firebaseUser.photoUrl.toString())
        val userDao = UserDao()
        userDao.allUser(user)

        /*Go to another Activity*/
        activity?.let { Navigation.findNavController(it, R.id.fragmentContainerView) }
            ?.navigate(R.id.homeFragment)
    }
}

Result

Firestore user post Entity Insert

java > models > Post. kt class

data class Post(
    val text: String = "",
    val createdBy: User = User(),
    val createdAt: Long = 0L,
    val likeBy: ArrayList<String> = ArrayList()
)

java > daos> UserDao.kt class (Some modify)

class UserDao {
    private val db = FirebaseFirestore.getInstance()
    private val userCollection = db.collection("users")

    fun allUser(user: User?){
        user?.let {
            GlobalScope.launch(Dispatchers.IO) {
                userCollection.document(user.uid).set(it)
            }
        }
    }
    
    /* add this getUserById()*/
    fun getUserById(uID: String): Task<DocumentSnapshot> {
        return userCollection.document(uID).get()
    }
}

java > daos> PostDao.kt class

class PostDao{

    private val auth = Firebase.auth
    private val db = FirebaseFirestore.getInstance()
    private val posCollections = db.collection("posts")

    fun addPost(text: String){
        val currentUser = auth.currentUser!!.uid

        GlobalScope.launch {
            val userDao = UserDao()
            val user = userDao.getUserById(currentUser).await().toObject(User::class.java)!!
            val currentTime = System.currentTimeMillis()
            val post = Post(text, user, currentTime)
            posCollections.document().set(post)
        }
    }
}

XML Design

<EditText
    android:id="@+id/postEt"
    android:layout_width="0dp"
    android:layout_height="200dp"
    android:layout_margin="12dp"
    android:background="@drawable/edit_text_round_shape"
    android:gravity="top"
    android:hint="What do you want to talk about?"
    android:padding="12dp"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<Button
    android:id="@+id/postBtn"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_margin="12dp"
    android:text="Post"
    android:background="@drawable/edit_text_round_shape"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/postEt" />

Activity

private lateinit var postDao: PostDao

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    postDao = PostDao()

    binding.postBtn.setOnClickListener {
        val postText = binding.postEt.text.toString().trim()
        if(postText.isNotEmpty()){
            postDao.addPost(postText)
        }
    }
}

Result

Firebase Cloud Firestore

Written by Papon Ahasan