MainActivity.kt
package com.example.jetpack
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.BatteryManager
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import java.math.RoundingMode
import java.text.DecimalFormat
class MainActivity : AppCompatActivity() {
// initialize a new broadcast receiver instance
private val receiver:BroadcastReceiver = object: BroadcastReceiver(){
override fun onReceive(context: Context?, intent: Intent?) {
// get battery voltage in Millivolts from intent
val voltage = intent?.getIntExtra(
BatteryManager.EXTRA_VOLTAGE, 0
)
voltage?.apply {
// show the battery voltage in volts
textView.text = "Battery Voltage\n\n$toVolts"
}
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// initialize a new intent filter instance
val filter = IntentFilter(Intent.ACTION_BATTERY_CHANGED)
// register the broadcast receiver
registerReceiver(receiver,filter)
}
}
// extension property to convert milli volts to volts
val Int.toVolts:String
get() {
// convert Millivolts to Volts
val volts = this * 0.001
// initialize a new decimal format instance
val decimalFormat = DecimalFormat("#.#")
// round the number using decimal format
decimalFormat.roundingMode = RoundingMode.CEILING
// format the decimal value to one decimal position
return "${decimalFormat.format(volts)} Volts"
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
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:id="@+id/constraintLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#EDEAE0"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:fontFamily="sans-serif-condensed"
android:gravity="center"
android:padding="32dp"
android:textColor="#0014A8"
android:textSize="35sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.25"
tools:text="TextView" />
</androidx.constraintlayout.widget.ConstraintLayout>

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