MainActivity.kt
package com.cfsuman.jetpack
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import java.util.*
class MainActivity : AppCompatActivity() {
private lateinit var mModel: RandomNumberViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Get the view model
mModel = ViewModelProviders.of(this).get(RandomNumberViewModel::class.java)
// Create the observer which updates the ui
val randomNumberObserver = Observer<Int>{newNumber->
// Update the ui with current data
textView.text = "Current Number : $newNumber"
}
// Observe the live data, passing in this activity as the life cycle owner and the observer
mModel.currentRandomNumber.observe(this,randomNumberObserver)
// Button click listener
button.setOnClickListener{
// Change the data
mModel.currentRandomNumber.value = Random().nextInt(50)
}
}
}
RandomNumberViewModel.kt
package com.cfsuman.jetpack
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
class RandomNumberViewModel:ViewModel(){
// Create a LiveData with a random number
val currentRandomNumber:MutableLiveData<Int> by lazy {
MutableLiveData<Int>()
}
}
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="Generate New Random Number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/button"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginStart="8dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintHorizontal_bias="0.454"
android:layout_marginTop="32dp"
app:layout_constraintTop_toTopOf="parent"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/textView"
android:text="Live Data"
android:textAppearance="@style/TextAppearance.AppCompat.Large"
android:layout_marginTop="32dp"
app:layout_constraintTop_toBottomOf="@+id/button"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
android:layout_marginStart="8dp"
app:layout_constraintStart_toStartOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
gradle dependencies
def lifecycle_version = "2.0.0"
// ViewModel and LiveData
implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"



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