Creating a Realm Database and Populating it using JSON File in Android

Repository

https://github.com/realm/realm-java

Retrofit Image

What Will I Learn?

• How to create a Realm Objects and save to it using JSON File
• How to use the Lombok plugin.
• How to use the RealmRecyclerViewAdapter and its subclasses.
• How to use the InputStream to read from raw files.

Requirements

• An Integrated Development Environment(IDE) for building Android Application(e.g Anroid Studio, IntelliJ)
• An Android Device or a Virtual Device.
• Java Programming Experience.
• Of course, willingness to learn

Resources

• Retrofit Website. https://realm.io/
• Retrofit Github. - https://github.com/realm
• Retrofit License - Apache License

Difficulty

• Intermediate

Description

Tutorial Overview

In this tutorial, we are going to be learning on how to create a realm database and populate the database using a json file and in order to teach this, we are going to be creating a fruit list application which will be using a recyclerview to show the fruit Image, Name and Price.

In computing, JavaScript Object Notation or JSON is an open-standard file format that uses human-readable text to transmit data objects consisting of attribute–value pairs and array data types (or any other serializable value). It is a very common data format used for asynchronous browser–server communication, including as a replacement for XML in some AJAX-style systems.

Source - https://en.wikipedia.org/wiki/JSON

We are also going to be using the Lombok plugin/library (https://projectlombok.org) to inject Getter and Setter methods using the @Getter and @Setter annotations.

Outline

User Dependencies (01:13 - 02:33)

• implementation 'com.jakewharton:butterknife:8.8.1'
  annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

The Butterknife plugin is used to make the injection of views in our activity java class file easier and simpler.

All you have to do is insert your cursor on the layout file then press alt + ins on a windows pc , select the Generate Butterknife Injection option and then select the views (Edittext, TextView , Button etc) and then click the confirm button.

• implementation 'io.realm:android-adapters:2.1.0'

The relam adapter plugin makes it possible that we use the RealmRecyclerViewAdapter instead of the default RecyclerViewAdapter which makes databinding a lot easier and less stresful as you will see in the tutorial.
(09:20 - 18:31)

• implementation 'org.projectlombok:lombok:1.16.20'
  annotationProcessor 'org.projectlombok:lombok:1.16.20'

The lombok library makes the creation of getter and setter methods easier just by including the @Getter and @Setter annotations on the fields. (07:38 - 09:07)

• implementation 'com.squareup.picasso:picasso:2.71828'

The Picasso plugin/library is used to load images.

Including RecyclerView into xml and Creating Single row Layout (02:35 - 05:53)

Inorder to display the list of fruits, we create a recycler view that will fill the screen by setting its height and weight properties to match_parent with an id of fruitsRecView. The id is useful for us when we inject the recyclerview in our activity java class file using ButterKnife.

Also, to display the list of fruits inside the recycler view, we must create a layout file that will determine how each list will look.

Inorder to achieve the above layout, we create a new layout resource file by right clicking on our res folder and selecting new resource file as shown in the image below.

We insert three views - ImageView , and then two TextViews which will be used to display the image of the Fruit and the price and name.

Creating JSON file in raw android repository Folder (05:53 - 07:46)

Inorder to create our json file, we have to save it in the raw android repository folder, the JSON file contains Five JSON objects with three fields - Image , Name , Price which will as the name implies display the Image, Price and Name of each fruit.

Creation Of Model Class (07:46 - 09:07)

For us to correctly be able to display the details of the fruits from the JSON file, we must have an appropraite model class that will be used to get and set the details of the fruits.

The Fruits model is created and since we are intending to use it as our realm class, it must extend the RealmObject class.

We finally use the lombok library to set the gettr and setter methods of the fields.

Creating our custom Adapter (09:22 - 18:31)

To bind the views from the single_fruit_row into our recyclerview, we create a custom Adapter - FruitsAdapter that extends from the RealmRecyclerViewAdapter where we use the onCreateViewHolder() method to inflate the single_fruit_row layout file and also use the onBindViewHolder() method to set the neccesary details of each row of fruits.

The FruitsViewHolder class uses ButterKnife to bind the views in the single_fruit_row so that they can be accessable in the onBindViewHolder() method.

Linking Everything Together (18:43 - 24:23)

In our MainActivity.java class file, we create the Realm database and populate it in our fillUpDatabase() method where we use an InputStream variable that opens a Raw resource file which is our JSON file (fruits.json).

We then create the realm objects from the json file using the createAllFromJson() method and passing the Fruits model as the first parameter and the inputStream variable as the second arguement.

Next we get all the objects of Fruits type from the realm database using the realm.where().findAll() method store in a RealmResults variable and pass this to our custom Adapter and then set a vertical LinearLayoutManager as the layout manager of the recycler view and then set its fix size - .setHasFixedSize() to true.

Video Tutorial

Application Execution

Related Videos

Creating a Contact Saving Android Application with Realm Database

• Creating a Contact Saving Android Application with Realm Database - PART 1
• Creating a Contact Saving Android Application with Realm Database - PART 2
• Creating a Contact Saving Android Application with Realm Database - PART 3
• Creating a Contact Saving Android Application with Realm Database - PART 4

• Retriving Data from MySql Database and Saving them in Realm Database in Android

Tutorial codes can be gotten from this GitHub repository: https://github.com/generalkolo/Realm-JSON

Proof of Work

https://github.com/generalkolo