Tuesday, February 26, 2019

android kotlin - Room RecyclerView LiveData example

MainActivity.kt 

package com.cfsuman.jetpack

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.activity_main.*
import org.jetbrains.anko.doAsync
import java.util.*


class MainActivity : AppCompatActivity() {

    private lateinit var model: StudentViewModel

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

        // Get the view model
        model = ViewModelProviders.of(this).get(StudentViewModel::class.java)

        // Specify layout for recycler view
        val linearLayoutManager = LinearLayoutManager(
            this, RecyclerView.VERTICAL,false)
        recyclerView.layoutManager = linearLayoutManager

        // Observe the model
        model.allStudents.observe(this, Observer{ students->
            // Data bind the recycler view
            recyclerView.adapter = RecyclerViewAdapter(students)
        })

        // Insert data into table
        btn.setOnClickListener {
            doAsync {
                model.insert(Student(null, UUID.randomUUID().toString()))
            }
        }
    }
}
RoomSingleton.kt 

package com.cfsuman.jetpack

import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase
import android.content.Context


@Database(entities = arrayOf(Student::class), version = 1, exportSchema = false)
abstract class RoomSingleton : RoomDatabase(){
    abstract fun studentDao():StudentDao

    companion object{
        private var INSTANCE: RoomSingleton? = null
        fun getInstance(context:Context): RoomSingleton{
            if (INSTANCE == null){
                INSTANCE = Room.databaseBuilder(
                    context,
                    RoomSingleton::class.java,
                    "roomdb")
                    .build()
            }

            return INSTANCE as RoomSingleton
        }
    }
}
RoomEntity.kt 

package com.cfsuman.jetpack

import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity(tableName = "studentTbl")
data class Student(
    @PrimaryKey
    var id:Long?,

    @ColumnInfo(name = "uuid")
    var name: String
)
RoomDao.kt 

package com.cfsuman.jetpack

import androidx.lifecycle.LiveData
import androidx.room.Dao
import androidx.room.Insert
import androidx.room.OnConflictStrategy
import androidx.room.Query

@Dao
interface StudentDao{
    @Query("SELECT * FROM studentTbl ORDER BY id DESC")
    fun allStudents(): LiveData<List<Student>>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun insert(student: Student)
}
StudentViewModel.kt 

package com.cfsuman.jetpack

import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import android.app.Application


class StudentViewModel(application:Application): AndroidViewModel(application){
    private val db:RoomSingleton = RoomSingleton.getInstance(application)
    internal val allStudents : LiveData<List<Student>> = db.studentDao().allStudents()

    fun insert(student:Student){
        db.studentDao().insert(student)
    }
}
RecyclerViewAdapter.kt 

package com.cfsuman.jetpack

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.custom_view.view.*

class RecyclerViewAdapter(val students: List<Student>)
    : RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>(){

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int)
            : RecyclerViewAdapter.ViewHolder {
        val v: View = LayoutInflater.from(parent.context)
            .inflate(R.layout.custom_view,parent,false)
        return ViewHolder(v)
    }

    override fun onBindViewHolder(holder: RecyclerViewAdapter.ViewHolder, position: Int) {
        holder.id.text = students[position].id.toString()
        holder.name.text = students[position].name
    }

    override fun getItemCount(): Int {
        return students.size
    }

    override fun getItemId(position: Int): Long {
        return super.getItemId(position)
    }

    override fun getItemViewType(position: Int): Int {
        return super.getItemViewType(position)
    }

    class ViewHolder(itemView:View): RecyclerView.ViewHolder(itemView){
        val id = itemView.tvId
        val name = itemView.tvName
    }
}
activity_main.xml 

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/rootLayout"
        tools:context=".MainActivity"
        android:background="#fdfdfc">
    <Button
            android:text="Insert Data"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btn"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="parent"
            android:layout_marginStart="8dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="8dp"/>
    <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="8dp"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginStart="8dp"
            app:layout_constraintHorizontal_bias="0.0"
            android:layout_marginBottom="8dp"
            app:layout_constraintBottom_toBottomOf="parent"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toBottomOf="@+id/btn"/>
</androidx.constraintlayout.widget.ConstraintLayout>
custom_view.xml 

<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.card.MaterialCardView
    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="wrap_content"
    app:contentPadding="10dp"
    android:layout_margin="3dp"
    app:cardElevation="2dp"
    app:cardMaxElevation="3dp">
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <TextView
            android:id="@+id/tvId"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:text="100"
            android:layout_margin="10dp"
            app:layout_constraintBottom_toBottomOf="parent"
            android:layout_marginBottom="8dp"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginStart="8dp"/>
        <TextView
            android:id="@+id/tvName"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            tools:text="dsfdfdsfdfdf"
            android:layout_marginTop="4dp"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="8dp"
            app:layout_constraintStart_toEndOf="@+id/tvId"
            android:layout_marginStart="8dp"
            app:layout_constraintHorizontal_bias="0.0"
            android:layout_margin="10dp"
        />
    </androidx.constraintlayout.widget.ConstraintLayout>
</com.google.android.material.card.MaterialCardView>
gradle settings 

apply plugin: 'kotlin-kapt'

dependencies {
    // Material components theme
    implementation 'com.google.android.material:material:1.0.0'

    // ViewModel and LiveData
    def lifecycle_version = "2.0.0"
    implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"

    // Room support
    def room_version = "2.1.0-alpha04"
    implementation "androidx.room:room-runtime:$room_version"
    kapt 'androidx.room:room-compiler:2.1.0-alpha04'

    // Anko Commons
    implementation "org.jetbrains.anko:anko-commons:0.10.5"

    // RecyclerView
    implementation 'androidx.recyclerview:recyclerview:1.0.0'
}
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