Building a Cryptocurrency with Kotlin : Part 1

Kotlin has been becoming more and more mature with every release. We arguably have the most concise modern programming language that currently exists. With language idioms like data classes, extensions, kotlin objects, delegated properties, lambdas and of course, the latest version of Kotlin adds coroutine support. Lets talk about Node.js for a second. Node.js helped us to create many amazing websites and services, and provides numerous modules to make our lives as developers easier. But just because a tool is good enough does not mean we should stop innovation there. Kotlin is now Node.js' competitor because Kotlin's powerful language idioms enable us to create a powerful and fast framework for building asynchronous servers and clients, called Ktor.

Lets go back in time for a moment. Back in 2008 a small C++ side project was started by Satoshi Nakamoto. This project would change the world for ever. 10 years later Bitcoin managed to inspire dozens of crypto currency projects, i…

Android Architecture Components meets Data Binding : Lifecycle awareness!

Finally Android Data Binding library got updated to play nice with Android Architecture Components library and became life-cycle aware! This means that any changes to the LiveData objects will be reflected in the layouts... automagically! :)
* Tested on Android Studio 3.1 - canary 6

Whats new?
To make the binding life-cycle aware you need to pass the life-cycle owner to the ViewDataBinding by calling the setLifecycleOwner method.

The ViewModel: Our view model consists of the LiveData object that is simply and observable data container, where the observer gets notified of data changes.

The model: Our model has one field that is used to store user's name. A POJO.

The layout:-Out layout consists of a text field that is bound to the user's name. And will be updated when our LiveData container posts a change.
-We also have an EditText that is two-way bound to the user's name, meaning when text gets entered, the name is updated and vise-versa, when the user LiveDate is updated t…

Android Lists Made Easy: DataBinding + RecyclerViewBindingAdapter Library

RecyclerViewBindingAdapter LibraryThis library provides a powerful yet reusable RecyclerView adapter that leverages ObservableArrayList and DataBinding to simplify your life. Tell the adapter which layouts your models map to and then just modify your observable list and the adapter takes care of the rest. Its that simple! Check out the library and example app source code here.

Step 1:
Add jitpack repository to you project's build.gradlefile

Step 2:Enable Android data binding and add library dependency in the module's build.gradle file that you will be using the library in. You will need data binding to create layouts bound to ViewModels. The adapter dynamically creates all the rows and manages recycling of the layouts.

Step 3:
Create ObservableArrayList that will hold all the view models and initialize EasyRecyclerAdapter with it. Set up the mappings between the layouts you intend to show in the list and the view model and the variable id (variable name) from the layout's<…

Android Architecture Components : ViewModel

ViewModel : UI-Related Data ObjectOne of the biggest challenges for an Android developer is keeping data across configuration changes such as screen rotation or during the recreation of Activity/Fragments after its been destroyed and recreated by the framework. Luckily the new Android Architecture Components library has ViewModel class that is intended to store and manage UI-related data so that the data survives configuration changes.  BenefitsKeeps data across UI recreationNo need to repeat API calls and Database queries on UI recreation Keeps Activity/Fragments clean since work is now delegated to ViewModelsShare ViewModels between Fragments Subclass ViewModel
To create a view-model just subclass ViewModel. View-models are responsible to provide data and keep reference to it. Our TimerViewModel lazily initializes TimerLiveData which is a LiveData implementation of a timer that counts seconds, read more about TimerLiveData and what exactly LiveData is used for in my post here.

Android Architecture Components : LiveData

Live Data : Life-cycle aware Observables
As an Android developer you often have to work with data that is dynamic and changing with user input, device configuration changes, or even time changes. On top of this as a developer you have to respect the life-cycle of an Activity of Fragment that contains this dynamically changing data: stop updates onStop() or onPause() and restart the updates onStart() and onResume(). Examples of this is location data, countdown timers, user's list selections and any other type of dynamically changing data. Lets see how we can make these tasks easier using LiveData. We will demonstrate LiveData by creating a self contained timer.

Subclass LiveData LiveData object is set active when the observer's lifecycle is stated or resumed. And the LiveData object is set inactive when the observer's lifecycle is stopped or pause. In our TimerLiveData we start timer when onActive() is called and stop the timer when onInactive() is called. This way the obs…

Android Architecture Components : Room Persistence Library

Room: a SQLite object mapping library After many years and using countless 3rd party DAO libraries I am happy to finally introduce official Android solution to working with SQLite databases and it is called Room Persistence Library. Before we begin you can find code from this tutorial here.

SQL ReviewData is stored in tablesTable's rows contain entitiesTable's columns contain entity's fieldsRows can have id's (primary keys) and id's must be uniqueYou can create relationships between rows in different tables by referring to other row's id (foreign key)Index primary key columns for performanceUse SQL queries to find sort and filter the data from tables What is Room? Room is a library that uses annotations in your Java data models and your data access objects (DAO's) to generate database schema (table definitions) and SQLite queries. So you don't have to write all the SQLite queries from scratch and have logic for storing and retrieving your models from d…

Android Data Binding : Dynamic RecyclerView Adapter

One of the most common list design patterns that I encounter as Android developer is a list with a variation of the following:

Multiple row types. Expandable/Collapsible rows or sections. Load more/Scroll to load more. Delete rows/Sections. 
And all of these can be implemented in a generic manner with Android Data Binding library. You can write one adapter for all the RecycleViews in your app and use it to render all the common design patterns. Check out the source for the example in this tutorial here.

Final result:

Lets begin by defining our adapter:

public class RecyclerViewBindingAdapter extends RecyclerView.Adapter<RecyclerViewBindingAdapter.BindingViewHolder> { private ObservableList<AdapterDataItem> data; public RecyclerViewBindingAdapter(ObservableList<AdapterDataItem> data) { = data; data.addOnListChangedCallback(new ObservableListCallback()); } @Override public BindingViewHolder onCreateViewHolder(ViewGroup par…