Kotlin & Firebase Android App Guide
Kotlin Basics
Kotlin Basics
Variables
- var name = "Chatu" // mutable
- val age = 20 // immutable
Data Types: String, Int, Double, Boolean, Float, Char
Functions
fun sayHi(name: String): String {
return "Hi $name!"
Conditionals
if (age > 18) { ... } else { ... }
Loops
for (i in 1..5) { println(i) }
Classes
class Person(val name: String, val age: Int)
Kotlin & Firebase Android App Guide
Null Safety
var name: String? = null
How to Build an App Using Kotlin
How to Build an App Using Kotlin
1. Setup
- Install Android Studio
- Create New Project -> Empty Activity -> Language: Kotlin
2. Files
- MainActivity.kt: Code
- activity_main.xml: UI layout
3. UI Example (XML)
<Button android:id="@+id/btnClick" android:text="Click Me!" />
4. Connect UI in Kotlin
val btn = findViewById<Button>(R.id.btnClick)
btn.setOnClickListener {
Toast.makeText(this, "Clicked!", Toast.LENGTH_SHORT).show()
}
Kotlin & Firebase Android App Guide
5. Run on Emulator or Device
Firebase Integration
Firebase Integration Guide
Step 1: Firebase Project
- Go to console.firebase.google.com
- Add project -> App (Android) -> Enter package name
- Download google-services.json and place it in the app/ folder
Step 2: Dependencies
- project-level build.gradle: classpath 'com.google.gms:google-services:4.3.15'
- app-level build.gradle:
apply plugin: 'com.google.gms.google-services'
dependencies {
implementation 'com.google.firebase:firebase-database-ktx'
implementation 'com.google.firebase:firebase-auth-ktx'
Step 3: Initialize Firebase
FirebaseApp.initializeApp(this)
Step 4: Realtime Database
Kotlin & Firebase Android App Guide
- Add data:
val db = FirebaseDatabase.getInstance().reference
db.child("users").push().setValue(User("Alice", 25))
- Read data:
db.child("users").addValueEventListener(object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
for (data in snapshot.children) {
val user = data.getValue(User::class.java)
override fun onCancelled(error: DatabaseError) {}
})
Step 5: Firebase Auth (Optional)
FirebaseAuth.getInstance().createUserWithEmailAndPassword(email, password)
Data Class
data class User(val name: String? = null, val age: Int? = null)
