Get easily started with Firebase in Android Studio

Before I thought it was a hassle to get started with a new project with Android Studio for Firebase but there are now some great tools in Android Studio to speed up the process. My goal for this post is to show you how to get started with Firestore for a new app to your firebase account. I currently running Android Studio 4.0.1.

Lets go to and see at “Option 2: Add Firebase using the Firebase Assistant” which is what we want to do here.

  1. In your Android Studio, create a new Android Project. Note that even if you do this in Java instead of Kotlin it might work just fine, but can’t guarantee the experience to be the same.
Making a new project with language Kotlin and minimum SDK API 16 with a Basic Activity
  1. Open up File > Settings > Plugins > Firebase Services > and select Update to keep the Firebase services updated. In case you don’t have it installed, install it.
  2. Select Tools > Firebase to open the Assistant pane.
Selecting Firestore

Firebase Assistant Steps

  1. Click Connect to Firebase.
    Then we will get this popup where we just select our project then click Connect.
  2. The second step is what is the time saver for sure, click this button and you will be greeted with information that the program will add some things (dependencies) to your gradle files. Accept changes.

    Unfortunately it can happen that there there is an issue when trying to sync the gradle files. I got this generated in my build gradle file:
    classpath ‘’
    classpath ‘’

    An nice soul explained that changing from to (we have 4.3.3 in my case) to fixed the issue. This might work for you too if you are having such problem.
  3. You should get a check mark on step two, and now for third step, you finally get access to the Firestore library where you can start having fun, so start by copying or writing the code for the Firebase Firestore object:
    In Java (see image as well): FirebaseFirestore db = FirebaseFirestore.getInstance();
    In Kotlin (see image as well): val db = FirebaseFirestore.getInstance()
    into your main activity located somewhere in MainActivity inside your onCreate function, and remember to click ALT+ENTER to import the dependencies or write in the top of MainActivity:
How it looks when you’ve done step three.

Or it does look like this (with Kotlin)

Using Kotlin have different syntax

Add data step (4)

Cloud Firestore stores data in Documents, which are stored in Collections. Cloud Firestore creates collections and documents implicitly the first time you add data to the document. You do not need to explicitly create collections or documents.

Firebase > Firestore Step 4: Add Data

Collections and documents are created implicitly in Cloud Firestore. Simply assign data to a document within a collection. If either the collection or document does not exist, Cloud Firestore creates it.

Google Firebase Firestore

This means that you do not need to do these two steps below, but remember this place. This is where your documents will be created. Just for the sake of learning how documents “looks” in the Firebase UI, lets create a collection and a document.

Indicating the button where to create a Firestore collection
Your first document can be anything. Just make something to create the collection.

What is amazing with firestore is that you can just push in data anywhere without much preparation, all you need is just to connect to your Firebase project and it will just work from there on.

So why don’t we just paste the whole code block from step four into our OnCreate function and see the magic work for itself.

Below is my whole file of MainActivity where I have pasted the code from step 4 for writing data just after the db object declaration and initialization. Note that you must add a property for the TAG which is used in the example. Another change is that I changed my collection name from users to usersTest but it doesn’t matter, it is just the desired collection name that will be created. If you are writing in Java syntax will obviously be different but this is how my code looks so far after copying the sample code and pasting it into my activity.

package fileidea.firestore

import android.os.Bundle
import android.view.Menu
import android.view.MenuItem

class MainActivity : AppCompatActivity() {

    private val TAG = "MainActivity"

    override fun onCreate(savedInstanceState: Bundle?) {

        val db = FirebaseFirestore.getInstance()

        // Create a new user with a first and last name

        // Create a new user with a first and last name
        val user: MutableMap<String, Any> = HashMap()
        user["first"] = "Ada"
        user["last"] = "Lovelace"
        user["born"] = 1815

        // Add a new document with a generated ID

        // Add a new document with a generated ID
                .addOnSuccessListener { documentReference -> Log.d(TAG, "DocumentSnapshot added with ID: " + }
                .addOnFailureListener { e -> Log.w(TAG, "Error adding document", e) }

        findViewById<FloatingActionButton>( { view ->
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show()

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(, menu)
        return true

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        return when (item.itemId) {
   -> true
            else -> super.onOptionsItemSelected(item)

If everything is in order, the application when it starts should write one document to a new collection called usersTest, and this user has three fields: first, last and born with the specified data from above (Ada, Lovelace, 1815). Now to see if is actually writing, we can check the Logcat in Android Studio, and also in Firebase under Firestore. Let’s try start the application right now and be ready with your Logcat.

The Android Studio Logcat

Running the app can be done with SHIFT+F10.
Right away I got some problem installing the application, something with “Cannot fit requested classes in a single dex file.Try supplying a main-dex list” when running the application. What I did was adding an implementation and set using multiDexEnabled: true (see code block below). Referring to this StackOverFlow post.

My build.gradle (app) looked like this in the end with successful build:

apply plugin: ''
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: ''

android {
    compileSdkVersion 29

    defaultConfig {
        applicationId "fileidea.firestore"
        minSdkVersion 16
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        multiDexEnabled true
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), ''
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    kotlinOptions {
        jvmTarget = '1.8'

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.1.0'
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation ''
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'androidx.navigation:navigation-fragment-ktx:2.1.0'
    implementation 'androidx.navigation:navigation-ui-ktx:2.1.0'
    implementation ''
    implementation ''
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'


Error adding document PERMISSION_DENIED ?

If you got below error your FireStore rules are not open enough probably. Check the rules.

Logcat shows error when trying to adding documents

As we see above we can see that there is error when adding documents and that there are insufficient permissions. This most likely means that you need to go to FireBase and your project, and to Firestore and open up the rules for writing (see below). Also, remember, this rules are insecure and should not be used in production.

Seeing the succesful result

The successful document write should look like this:

Let’s take a look at the Database tab in the administration page of Firebase of your project

Select Database then FireStore if asked

We can then confirm that we got the documents in Firestore! This is how to get started with FireStore in Android Studio by just connecting basically and pasting in some code. Of course, how it is up to you to make a nice design and functionality. In similar ways you can read data by following the steps in Android Studio as well, pretty much the same thing!

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