Android Architecture Components - Room - Kotlin

-

Introduction:

Google's Android Architecture components became stable now. It is nothing but a collection of libraries that ease our Android Development.

Android Architecture Components:


Let's see about Room in this post. 

Room is a new way to create a database in your Android Apps. 

SQLite vs Room:

The following are some of the advantages of Room over SQLite.

(a) In SQLite, there is no compile-time verification of SQL queries, whereas Room verifies it.
(b) We need to write lots of boilerplate codes to convert SQL queries to Java Objects.
(c) We need to update the affected SQL queries manually, while the schema changes in SQLite. Whereas, Room will take care of it automatically.

Room Architecure and Components:

Three components are there in Room:

(1) Database is a holder class that uses annotation to define the list of entities (i.e., tables) and database version. 
(2) Entity - represents a table within the database
(3) DAO (Database Access Objects) - Contains methods used for accessing database.

Code:

build.gradle (module level gradle):

Include the following in your module - level gradle.


apply plugin: 'kotlin-kapt'

compile 'com.android.support:recyclerview-v7:27.0.2'
compile 'com.android.support:cardview-v7:27.0.2'
compile "android.arch.persistence.room:runtime:1.0.0"
kapt "android.arch.persistence.room:compiler:1.0.0"

dialog.xml:

Design a layout to show as dialog while adding/inserting data to the created Table in Database.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="10dp">

    <android.support.design.widget.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.design.widget.TextInputEditText
            android:id="@+id/name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Book Name" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.design.widget.TextInputEditText
            android:id="@+id/author"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Author" />
    </android.support.design.widget.TextInputLayout>


    <android.support.design.widget.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1">

        <android.support.design.widget.TextInputEditText
            android:id="@+id/genre"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Genre" />
    </android.support.design.widget.TextInputLayout>


    <TextView
        android:id="@+id/submit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dp"
        android:layout_marginTop="20dp"
        android:background="@color/colorPrimary"
        android:gravity="center"
        android:padding="15dp"
        android:text="Submit"
        android:textColor="@color/white" />

</LinearLayout>

db_layout.xml:

Let's design a layout to list the stored data in Recyclerview and a FloatingActionButton to add new data to the database.

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@drawable/add"
        app:elevation="2dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</android.support.constraint.ConstraintLayout>

Book.kt (Entity - Class)

Entity is nothing but Table in Database. In Kotlin, we can define the Entity class as same as data class with so much ease. By default, the class name "Book" will be considered as Table name. If you need to assign a different name, you have define that as follows:
@Entity(tableName = "book_table")

data class Book(var bookName : String)


Likewise, if we need to change columnName of Table ,

data class Book(@ColumnInfo(name = "book_name")var bookName : String)











Each table should contain one PrimaryKey, it can be added manually or auto generated. In this example, we are adding that autogenerate.



So, Our Book.kt class will be like as follows:








@Entity
data class Book(var bookName : String, var author : String,
                var genre : String){
    @PrimaryKey(autoGenerate = true)
    var id : Long? = null
}






BookDao.kt (Dao - Interface)





Dao interface contains all queries that will be used to process Database.








@Dao
interface BookDao {
    @Query("SELECT * FROM Book")
    fun getBookInfo() : MutableList<Book>

    @Insert
    fun addBook(book : Book)

    @Update(onConflict = REPLACE)
    fun updateBook( book: Book)

    @Delete
    fun deleteBook( book: Book)
}








MyDatabase.kt (Database - Class)





Database class should be declared once like Singleton class and can be accessed throughout the app. It should include array of entities and version of Database. In Kotlin, there is no static keyword. But it can be replaced with companion object. Also, do remember that every database operations should be done only in Background thread. Otherwise the app will crash.










@Database(entities = arrayOf(Book::class), version = 1)
abstract class MyDatabase : RoomDatabase() {
    abstract fun bookDao(): BookDao

    companion object {
        var INSTANCE: MyDatabase? = null

        fun getInstance(context: Context): MyDatabase {

            if (INSTANCE == null) {
                INSTANCE = Room.databaseBuilder(context.applicationContext, MyDatabase::class.java, "Books.db").build()
            }
            return INSTANCE as MyDatabase;
        }

        @SuppressLint("StaticFieldLeak")
        fun insertData(mydata: MyDatabase, book: Book) {
            object : AsyncTask<Void, Void, Void>() {
                override fun doInBackground(vararg voids: Void): Void? {
                    mydata.bookDao().addBook(book)
                    return null
                }
            }.execute()
        }

        @SuppressLint("StaticFieldLeak")
        fun getData(mydata: MyDatabase): MutableList<Book> {
            lateinit var lists: MutableList<Book>

            return object : AsyncTask<Void, Void, MutableList<Book>>() {
                override fun doInBackground(vararg voids: Void): MutableList<Book>? {
                    lists = mydata.bookDao().getBookInfo()
                    return lists
                }
            }.execute().get()
        }
    }
}





RecyclerAdapter.kt (Adapter - Class)






class RecyclerAdapter(var context: Context, var data : List<Book>) : RecyclerView.Adapter<RecyclerAdapter.Holder>() {
    override fun onBindViewHolder(holder: Holder?, position: Int) {
        holder?.bindItems(data.get(position))
    }

    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): Holder {
        val v = LayoutInflater.from(context).inflate(R.layout.recycler_item, parent, false)
        return Holder(v)
    }

    override fun getItemCount(): Int = data.size

    class Holder(itemView: View?) : RecyclerView.ViewHolder(itemView) {
        fun bindItems(book: Book){
            itemView.name.text = book.bookName
            itemView.author.text = book.author
            itemView.genre.text = book.genre
        }

    }
}










DbActivity.kt





Finally, we can fetch data from Database and add it to our list and set it to our recyclerview's adapter. In FloatingActionButton's click event, a dialog will be opened. There the details of the book can be added and stored into the database. Now its done.








class DbActivity : AppCompatActivity() {

    lateinit var adapter: RecyclerAdapter
    lateinit var list: MutableList<Book>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.db_layout)

        list = MyDatabase.getData(MyDatabase.getInstance(this))

        recyclerView.layoutManager = LinearLayoutManager(this)
        adapter = RecyclerAdapter(this, list)
        recyclerView.adapter = adapter

        add.setOnClickListener {
            openDialog()
        }

    }

    private fun openDialog() {
        val dialog = Dialog(this)
        dialog.requestWindowFeature(Window.FEATURE_NO_TITLE)
        dialog.setContentView(R.layout.dialog)
        val lp: WindowManager.LayoutParams = WindowManager.LayoutParams().apply {
            copyFrom(dialog.window.attributes)
            width = WindowManager.LayoutParams.MATCH_PARENT
            height = WindowManager.LayoutParams.WRAP_CONTENT
        }

        val submit = dialog.findViewById<View>(R.id.submit) as TextView
        val name = dialog.findViewById<View>(R.id.name) as EditText
        val author = dialog.findViewById<View>(R.id.author) as EditText
        val genre = dialog.findViewById<View>(R.id.genre) as EditText

        submit.setOnClickListener {
            when {
                name.length() == 0 || author.length() == 0 || genre.length() == 0 ->
                    Toast.makeText(this@DbActivity, "Please fill all the fields"
                            , Toast.LENGTH_SHORT).show()

                else -> {
                    val book = Book(name.text.toString(), author.text.toString(), genre.text.toString())
                    MyDatabase.insertData(MyDatabase.getInstance(this), book)
                    dialog.dismiss()
                    Handler().postDelayed({
                        list.clear()
                        list.addAll(MyDatabase.getData(MyDatabase.getInstance(this)))
                        adapter.notifyDataSetChanged()
                    }, 1000)
                }
            }
        }
        dialog.show()
        dialog.getWindow().setAttributes(lp)
    }
}






Run Application:





    























































Comments











Post a Comment








































Popular posts from this blog









SOAP Client using ksoap2 in Android - Kotlin






-














Image







            Introduction:     SOAP stands for Simple Object Access Protocol. It is XML-based protocol that allows programs that run on different operating systems (like Windows, Linux, etc) to communicate using HTTP and XML.   Pros:    Security - SOAP provides its own security known as WS Security .  Platform Independent - SOAP web services can be written in any programming language and executed in any platform    Cons:     Slow - It uses XML format that must be parsed, to be read. It defines many standards to be followed while developing. So its slow and consumes more bandwidth and resource.  WSDL dependent - It uses WSDL mechanism and doesn't have any other mechanism to discover the service.    Things to know:    The following are the things we have to know before we proceed further:                         URL  - It is the URL of WSDL file.                         NAMESPACE  - It is targetNamespace in WSDL.                                             METHOD_NAME  - It is the met








Read more










RecyclerView  with different number of columns using SpanSizeLookup






-














Image







         We already know how to design RecyclerView. But how to create RecyclerView with different columns depending on its row? Like below image?       Yeah, we can do that, by using two different layouts with different viewType on Adapter. Another way is do some logic to do so. But, it's cumbersome. Luckily, we have another simple way to do that using SpanSizeLookUp . Let's see how to implement that in this post.   Implementation:   build.gradle   Include the following in app-level gradle file.       implementation  'com.android.support:recyclerview-v7:27.0.2'    implementation  'com.android.support.constraint:constraint-layout:1.1.0-beta5'     recycler.xml    <?xml version= "1.0"  encoding= "utf-8" ?> <android.support.constraint.ConstraintLayout xmlns:android= "http://schemas.android.com/apk/res/android"      android:layout_width= "match_parent"      android:layout_height= "match_parent"      xmlns:ap








Read more










Using Camera in Android - Kotlin






-














Image







         Nowadays, most of our Android app require access to Camera to capture picture or Video. We can do that in two ways.                                  (i) Using built-in Camera,                                  (ii) Using custom Camera.   Using Built-in Camera  In this post, Let's see how to use the built-in camera to capture images and save it.     Its a simple way to capture pics. We can use the mobile's built-in camera app using Intent.      val REQUEST_IMAGE_CAPTURE =  1    private fun takePictureIntent() {       val takePictureIntent =  Intent(MediaStore . ACTION_IMAGE_CAPTURE)       if  (takePictureIntent . resolveActivity(packageManager) !=  null) {            startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE)       }  }           After the picture has been captured, the result will received on onActivityResult method. There, we can get the data, in Bitmap form.     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {    








Read more










Databinding in RecyclerView - Android - Kotlin






-














Image







 Hey Guyss!!   Already we have seen the basics of Databinding  and how to use it in previous  post .   Now let's see how to use Databinding  in RecyclerView . And Its gonna be a short post. ;)   You can find the Project in GitHub .   Prerequisite:  build.gradle   First, we have enable dataBinding in app-level build.gradle                             android {                                      dataBinding {                                              enabled = true                                      }                             }   Next, we have add the following plugin.                                 apply plugin: 'kotlin-kapt'    Next, we have to include dependency for databinding, (Not needed, if using Android Studio 3.2 or above, since its already bundled)                               kapt "com.android.databinding:compiler:3.2.0-alpha10"      Implementation:    We can directly bind the data to RecyclerView's Adapter layout. So, let's design the








Read more










Map, Location update and AutoComplete Places - Kotlin






-














Image







         Let's see how to show current location in Maps and also show the location which is chosen from AutoComplete in Maps with the updated Google play services. That is, for location listening we gonna use   FusedLocationProviderClient and for autocomplete places, we gonna use, GeoDataClient with AutoCompletePrediction, i.e., no need to call places url from our end, Google Playservices will do that work for you. Okiee, Let's start now.   You can find the project in Github .   PreRequisite:  Navigate to  https://developers.google.com/maps/documentation/android-api/signup  and do as per the instructions to start.   Manifest:   Include your API key, which you got from previous step in AndroidManifest.xml              <meta-data             android:name= "com.google.android.geo.API_KEY"              android:value= "AIzXXXXXXXXXX_XXXXXXXXXXXXXX"  />     Gradle:  Include the following in app-level build 's dependencies.         implementation 'com








Read more










Room with LiveData, ViewModel - Android Architecture Components - Kotlin






-














Image







              Introduction:     We have already learnt about Room in last post,  Room-Kotlin . In this post, lets learn about how to use ViewModel and LiveData with Room to improve usablity. Using LiveData with Room, allows views to be notified about data changes automatically.   LiveData:    LiveData is nothing but observable data holder class. It allows us to observer changes in data across multiple components of app. It is also aware of and respects lifecycle of Activities/Fragments. It also ensures that LiveData only updates app component observers that are in an active lifecycle state.     The following image depicts the Lifecycle and States:     Here, CREATED, STARTED, RESUMED - Active States            INTIALIZED, DESTROYED - InActive States   So, LiveData will remove the updates automatically while in InActive States, i.e., INTIALIZED and DESTROYED.   ViewModel:    ViewModel is an entity that is free of Activity/Fragment's lifecycle. So it allows us to store and manage UI-r








Read more










Stripe Integration in Android - Kotlin






-














Image







           Stripe is one of the simplest payment gateway to be used. It enables us to process payments in minutes. Let's see how to integrate Stripe in Android using Kotlin.    Operational Flow:                   1. App should provide order details to Stripe server and the order total will be returned to App.              2. Then the user will enter the payment/card details. That will be sent to Stripe server and the result of the request will be sent back to the App.    Create Stripe Account:   (a) Go to  https://dashboard.stripe.com/register  and enter all your details and create account.          (b) Click API in side tab. Make sure that the Account is in Test mode. And make a note of          Publishable Key and Secret Key for use.           Code:    build.gradle:     compile 'com.stripe:stripe-android:5.1.0'    Layout files:    main_layout.xml:    <?xml version="1.0" encoding="utf-8"?>   <android.support.constraint.ConstraintLayout xmlns:an








Read more










Braintree Integration in Android - Kotlin






-














Image







            Let’s learn how to integrate Braintree in Android app with Kotlin. Braintree is a subsidary of PayPal.  It focuses in helping businesses of all size and to help maximize business growth. Braintree accepts  the following payments:                                                            * Credit Cards                              * Venmo                             * Android Pay                             * Apple Pay                             * PayPal        Operation Flow:              1. App have to request token from the server.       2. Server have to generate a token using Braintree’s SDK and send that to the requested App.       3. With that Token, app should allow user to pay, which will be validated by Braintree’s server and              then the payment nonce will be received.       4. That received payment nonce and paid amount will be sent to our own server. There the             payment will be checked whether its successful or not and the response will be s








Read more










Exploring Android Slices - JetPack






-














Image







  Introduction:   Slices are a new way of embedding our app's content in other surfaces, like Google Search and later in other places like Google Assistant. Slices are UI templates, which gives look and feel at home in whatever surface, they get hosts in. Also they are rich, interactive and dynamically updatable.    Before jumping into that, first migrate your project to AndroidX, (Android Studio 3.2 & above), by navigating as,                                           Refactor --> Migrate  to AndroidX         Setup:   build.gradle        implementation 'androidx.slice:slice-core:1.0.0'     implementation 'androidx.slice:slice-builders-ktx:1.0.0-alpha6'     implementation 'androidx.slice:slice-builders:1.0.0'      Creating Slice Provider:   Slice Provider is a component that let us display the slices we are creating, on outside our application. We can create the Slice Provider by navigating,                                         File -> New ->








Read more










Android JetPack - Scheduling Tasks with WorkManager 






-














Image







            Introduction:    WorkManager is one of the Android JetPack component. It is specifically designed for scheduling and managing background tasks. If the app is running, task will be executed in a new thread. Otherwise, WorkManager automatically chooses an appropriate way to do so. It can be AlarmManager, JobScheduler or Firebase JobDispatcher, depends on device's API level and its dependencies.      WorkManager Basics:    Worker  WorkRequest  WorkManager  WorkInfo    (i) Worker:     It specifies what task need to be performed.     class  SampleWorker (context: Context, workerParams: WorkerParameters) : Worker(context, workerParams) {      override fun doWork (): ListenableWorker. Result  {         //do the work here         return  ListenableWorker. Result . SUCCESS      } }      (ii) WorkRequest:   It represents which Worker  should perform the task. Also we can specify any constraints/circumstances, based on which the task should be performed. Constraints  can be of Net








Read more