Part 1 – Introduction

Part 2 – Preparations & Set Document

Part 3 – Get Document

Part 4 – SnapshotListener

Part 5 – Merge & Update

Part 6 – Delete Field & Document

Part 7 – Custom Objects

Part 8 – Add & Retrieve Multiple Documents

Part 9 – Simple Queries

Part 10 – Compound Queries

Part 11 – OR Queries

Part 12 – Pagination

Part 13 – DocumentChanges

Part 14 – Batched Writes

Part 15 – Transactions

Part 16 – Arrays

Part 17 – Nested Objects

Part 18 – Subcollections

Part 1 – Introduction

In this tutorial we will learn, how to use the Cloud Firestore database to store and retrieve data in an Android app.

Firestore is a cloud-hosted database that makes it easy to synchronize data in realtime between multiple connected client apps and across different platforms, without us having to manage our own servers.
Firestore is a schemaless NoSQL database and stores it’s data in documents which each contain a set of key-value pairs (fields). These fields can be simple datatypes like strings, integers and booleans, but also geographical points, raw binary values, timestamps, arrays, nested objects (maps) etc.
Documents are organized into collections and can contain subcollections.

Links:

Explanation Firestore data model:
firebase.google.com/docs/firestore/data-model

Comparison Firestore vs Realtime Database:
firebase.google.com/docs/firestore/rtdb-vs-firestore

Part 2 – Preparations & Set Document

In part 2 of the Firestore tutorial, we connect a new Android Studio project to Firebase with help of the Firebase assistant and add the Firestore dependency.
When that’s done we upload our first document into our first collection, by retrieving the user input from 2 EditText fields, saving the input as strings in a HashMap together with their keys, and passing this HashMap to Firestore over a database reference that we get with the static Firestore getInstance method. For this we simply call the collection and document reference methods on our Firestore reference, pass strings for their names and lastly call the set method to pass our Map to this reference and set it as the fields on our first document.
We also add an OnSuccessListener and an OnFailureListener to have callbacks about the upload success.

Add dependencies in gradle file from the official link of firebase:-

https://firebase.google.com/docs/android/setup

In activity_main.xml file add these lines:-

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp"
tools:context="com.codinginflow.firestoreexampleproject.MainActivity">

<EditText
android:id="@+id/edit_text_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Title"
android:inputType="text" />

<EditText
android:id="@+id/edit_text_description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Description"
android:inputType="text" />

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="saveNote"
android:text="Save" />

</LinearLayout>

In MainActivity.java class file add these lines of codes:-

import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.FirebaseFirestore;

import java.util.HashMap;
import java.util.Map;

public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";

private static final String KEY_TITLE = "title";
private static final String KEY_DESCRIPTION = "description";

private EditText editTextTitle;
private EditText editTextDescription;

private FirebaseFirestore db = FirebaseFirestore.getInstance();

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

editTextTitle = findViewById(R.id.edit_text_title);
editTextDescription = findViewById(R.id.edit_text_description);
}

public void saveNote(View v) {
String title = editTextTitle.getText().toString();
String description = editTextDescription.getText().toString();

Map<String, Object> note = new HashMap<>();
note.put(KEY_TITLE, title);
note.put(KEY_DESCRIPTION, description);

db.collection("Notebook").document("My First Note").set(note)
.addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void aVoid) {
Toast.makeText(MainActivity.this, "Note saved", Toast.LENGTH_SHORT).show();
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Toast.makeText(MainActivity.this, "Error!", Toast.LENGTH_SHORT).show();
Log.d(TAG, e.toString());
}
});
}

}

Part 3 – Get Document

In part 3 of the Firestore tutorial, we retrieve our uploaded document by calling the get method on our DocumentReference. As before we add an OnSuccessListener where we get a DocumentSnapshot that contains the data of our document. We can either retrieve our values directly by passing the key for each value to the DocumentSnapshot’s getString method, or alternatively recreate our original Map as a whole.
In the OnFailure method we print the exception to the stacktrace.

Add dependencies in gradle file from the official link of firebase:-

https://firebase.google.com/docs/android/setup

In activity_main.xml add these codes:-

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

android:padding="16dp"

tools:context="com.codinginflow.firestoreexampleproject.MainActivity">

<EditText

android:id="@+id/edit_text_title"

android:layout_width="match_parent"