KotlinMessenger

Pratice Android Application that features a fully functional chat messaging environment.

User to User messaging

To send and receive messages the app saves a list of messages under a node in Firebase Database. Next, it listens for all these messages as they are entered in the system, and then refreshes the adapter items in real time.

private fun performSendMessage() {
        //Get sender info
        val text = edittext_chat_log.text.toString()
        val fromId = FirebaseAuth.getInstance().uid
        //Get receiver info
        val user = intent.getParcelableExtra<User>(NewMessageActivity.USER_KEY)
        val toId = user?.uid
        if (fromId == null) return
        //Push messages to each user message's list on the RealTimeDatabase
        val reference =
            FirebaseDatabase.getInstance().getReference("/user-messages/$fromId/$toId").push()
        val toReference =
            FirebaseDatabase.getInstance().getReference("/user-messages/$toId/$fromId").push()
        val chatMessage =
            ChatMessage(reference.key!!, text, fromId, toId!!, System.currentTimeMillis() / 1000)
        reference.setValue(chatMessage)
            .addOnSuccessListener {
                Log.d(TAG, "Saved chat message: ${reference.key}")
                edittext_chat_log.text.clear()
                recyclerview_chat_log.scrollToPosition(adapter.itemCount - 1)
            }
        toReference.setValue(chatMessage)
        //Update Latest message to the recently uploaded message
        val latestMessageRef =
            FirebaseDatabase.getInstance().getReference("/latest-messages/$fromId/$toId")
        latestMessageRef.setValue(chatMessage)
        val latestMessageToRef =
            FirebaseDatabase.getInstance().getReference("/latest-messages/$toId/$fromId")
        latestMessageToRef.setValue(chatMessage)
    }

Latest Messages

The initial activity displays a list of users whom the currently logged user is messaging. Each adapter’s item also fetches the information from a specific Firebase node that monitors the latest messages saved.

private fun listenForLatestMessages() {
        val fromId = FirebaseAuth.getInstance().uid
        val ref = FirebaseDatabase.getInstance().getReference("/latest-messages/$fromId")
        //Fetch Latest Messages for each active conversation
        ref.addChildEventListener(object : ChildEventListener {
            override fun onChildAdded(p0: DataSnapshot, p1: String?) {
                val chatMessage = p0.getValue(ChatMessage::class.java) ?: return
                latestMessagesMap[p0.key!!] = chatMessage
                refreshRecyclerViewMessages()
            }
            override fun onChildChanged(p0: DataSnapshot, p1: String?) {
                val chatMessage = p0.getValue(ChatMessage::class.java) ?: return
                latestMessagesMap[p0.key!!] = chatMessage
                refreshRecyclerViewMessages()
            }
            override fun onCancelled(error: DatabaseError) {
            }
            override fun onChildMoved(snapshot: DataSnapshot, previousChildName: String?) {
            }
            override fun onChildRemoved(snapshot: DataSnapshot) {
            }
        })
    }

Firebase Auth

Using the Firebase Auth library users can be registered with email and password. They can create a username and upload a profile picture.
Integrating CircleImageView allows to round off the corners of the images

RecyclerView

Using Groupie library for easier adapter object creation.

//ViewHolder Class for outbound messages
        class ChatFromItem(val text: String, val user: User) : Item<GroupieViewHolder>() {
            override fun bind(viewHolder: GroupieViewHolder, position: Int) {
                viewHolder.itemView.textView_from_row.text = text
                val uri = user.profileImageUrl
                val targetImageView = viewHolder.itemView.imageView_from_row
                Picasso.get().load(uri).into(targetImageView)
            }
            override fun getLayout(): Int {
                return R.layout.chat_from_row
    }
}

• Remember to add your own Firebase credentials when you test the app, add your own google-services.json

Credits

Firebase analytics 17.5.0, auth 19.4.0, storage 19.2.0, database 19.4.0

Circle Image View 3.1.0

Groupie 2.8.1

Picasso 2.71828

Android Gradle plugin version: 4.0.1

Gradle version: 6.1.1

com.google.gms4.3.3

buildToolsVersion “30.0.1”

ext.kotlin_version = “1.4.0”

Gradle dependecies

    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.1'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.1'
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    implementation 'com.google.firebase:firebase-analytics:17.5.0'
    implementation 'com.google.firebase:firebase-auth-ktx:19.4.0'
    implementation 'com.google.firebase:firebase-storage-ktx:19.2.0'
    implementation 'com.google.firebase:firebase-database-ktx:19.4.0'
    implementation 'de.hdodenhof:circleimageview:3.1.0'
    implementation "com.xwray:groupie:2.8.1"
    implementation 'com.squareup.picasso:picasso:2.71828'