Ejemplo de cómo usar la batería en Android con Kotlin

BatteryInfo.kt

package com.webserveis.batterycheck

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.BatteryManager
import android.os.Build
import android.os.Bundle
import android.util.Log
import android.view.Menu
import android.view.MenuItem
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.app.AppCompatDelegate
import androidx.core.content.ContextCompat
import com.google.android.material.snackbar.Snackbar
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.main.content_main.*
import kotlin.math.roundToInt


/*
https://www.baeldung.com/java-to-kotlin
adb shell dumpsys battery set level 30

https://danielme.com/2016/01/23/android-tutorial-broadcast-receiver/
https://github.com/BharathVishal/AndroidBatteryStats/blob/master/app/src/main/java/androidbatterystats/bharathvishal/com/androidbatterystats/MainActivity.kt
21> ACTION_POWER_SAVE_MODE_CHANGED
*/
class MainActivity : AppCompatActivity() {

    companion object {
        val TAG: String = MainActivity::class.java.simpleName
    }

    //private lateinit var batteryPercent: WaveLoadingView


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)

        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)

        Log.d(TAG, "onCreate")

        //batteryPercent = findViewById<WaveLoadingView>(R.id.batteryPercent)

        fab.setOnClickListener { view ->

            if (isPlugged(this)) {
                Toast.makeText(this@MainActivity, "plugged!", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this@MainActivity, "unplugged!", Toast.LENGTH_SHORT).show()
            }

            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                .setAction("Action", null).show()
        }
    }


    override fun onStart() {
        super.onStart()
        registerReceiver(batteryChangeReceiver, IntentFilter(Intent.ACTION_BATTERY_CHANGED))
    }

    override fun onStop() {
        super.onStop()
        unregisterReceiver(batteryChangeReceiver)
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        return when (item.itemId) {
            R.id.action_battery_settings -> {
                val intentBatteryUsage = Intent(Intent.ACTION_POWER_USAGE_SUMMARY)
                startActivity(intentBatteryUsage)
                true
            }

            else -> super.onOptionsItemSelected(item)
        }
    }

    fun isPlugged(context: Context): Boolean {
        val batteryStatus: Intent? = IntentFilter(Intent.ACTION_BATTERY_CHANGED).let { ifilter ->
            context.registerReceiver(null, ifilter)
        }

        //original
        val plugged: Int = batteryStatus?.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1) ?: -1
        return plugged == BatteryManager.BATTERY_PLUGGED_AC || plugged == BatteryManager.BATTERY_PLUGGED_USB || plugged == BatteryManager.BATTERY_PLUGGED_WIRELESS

    }

    private val batteryChangeReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context?, intent: Intent?) {

            Log.i(TAG, "onReceive $intent")

            /*when (intent?.action) {
                Intent.ACTION_POWER_CONNECTED -> handleSomethingHappened()
            }*/

            val level: Int = intent!!.getIntExtra(BatteryManager.EXTRA_LEVEL, -1)
            val scale: Int = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
            val batteryPct: Float = level / scale.toFloat()

            val batteryInfo: BatteryInfo = BatteryInfo()
            batteryInfo.status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1)
            batteryInfo.level = batteryPct
            batteryInfo.chargePlug = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1)
            batteryInfo.health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH, BatteryManager.BATTERY_HEALTH_UNKNOWN)
            batteryInfo.voltage = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE, -1).toFloat()
            batteryInfo.temperature = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, -1)
            batteryInfo.technology = intent.getStringExtra(BatteryManager.EXTRA_TECHNOLOGY)

            Log.d(TAG, "batteryInfo $batteryInfo")

            lblBatteryStatus.text = getBatteryStatusString(batteryInfo.status)

            when (batteryInfo.chargePlug) {
                BatteryManager.BATTERY_PLUGGED_WIRELESS -> lblBatteryCharge.text =
                    getText(R.string.battery_plugged_wireless)
                BatteryManager.BATTERY_PLUGGED_AC -> lblBatteryCharge.text = getText(R.string.battery_plugged_ac)
                BatteryManager.BATTERY_PLUGGED_USB -> lblBatteryCharge.text = getText(R.string.battery_plugged_usb)
                else -> lblBatteryCharge.text = getText(R.string.battery_in_use)
            }

            lblBatteryHealth.text = getBatteryHealthString(batteryInfo.health)

            batteryPercent.progressValue = (batteryPct * 100).roundToInt()
            batteryPercent.centerTitle = (batteryPct * 100).roundToInt().toString() + " %"
            batteryPercent.setAnimDuration(3000L)

            when ((batteryPct * 100).toInt()) {
                in 31..100 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_green_600)
                in 11..30 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_yellow_500)
                in 0..10 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_red_500)
            }


            outputText.text = null

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_status_label).toString(),
                    getBatteryStatusString(batteryInfo.status)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_plugged_label).toString(),
                    getBatteryPluggedString(batteryInfo.chargePlug)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_level_label).toString(),
                    level
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_health_label).toString(),
                    getBatteryHealthString(batteryInfo.health)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_voltage_label).toString(),
                    batteryInfo.voltage
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_temperature_label).toString(),
                    (batteryInfo.temperature / 10).toFloat()
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_technology_label).toString(),
                    batteryInfo.technology
                ) + System.getProperty("line.separator")
            )

        }

    }

    private fun getBatteryStatusString(status: Int?): String {
        return when (status) {
            BatteryManager.BATTERY_STATUS_CHARGING -> getText(R.string.battery_status_charging).toString()
            BatteryManager.BATTERY_STATUS_DISCHARGING -> getText(R.string.battery_status_discharging).toString()
            BatteryManager.BATTERY_STATUS_FULL -> getText(R.string.battery_status_full).toString()
            BatteryManager.BATTERY_STATUS_NOT_CHARGING -> getText(R.string.battery_status_not_charging).toString()
            BatteryManager.BATTERY_STATUS_UNKNOWN -> getText(R.string.battery_status_unknown).toString()
            else -> ""
        }
    }

    private fun getBatteryPluggedString(plugged: Int?): String {
        return when (plugged) {
            BatteryManager.BATTERY_PLUGGED_WIRELESS -> getText(R.string.battery_plugged_wireless).toString()
            BatteryManager.BATTERY_PLUGGED_AC -> getText(R.string.battery_plugged_ac).toString()
            BatteryManager.BATTERY_PLUGGED_USB -> getText(R.string.battery_plugged_usb).toString()
            else -> getText(R.string.battery_plugged_not).toString()
        }
    }

    private fun getBatteryHealthString(health: Int?): String {
        return when (health) {
            BatteryManager.BATTERY_HEALTH_GOOD -> getText(R.string.battery_health_good).toString()
            BatteryManager.BATTERY_HEALTH_COLD -> getText(R.string.battery_health_cold).toString()
            BatteryManager.BATTERY_HEALTH_DEAD -> getText(R.string.battery_health_dead).toString()
            BatteryManager.BATTERY_HEALTH_OVERHEAT -> getText(R.string.battery_health_overheat).toString()
            BatteryManager.BATTERY_HEALTH_OVER_VOLTAGE -> getText(R.string.battery_health_over_voltage).toString()
            BatteryManager.BATTERY_HEALTH_UNSPECIFIED_FAILURE -> getText(R.string.battery_health_unspecified_failure).toString()
            else -> getText(R.string.battery_health_unknown).toString()
        }
    }

    private fun getBatteryCapacity(ctx: Context): Long {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            val mBatteryManager = ctx.getSystemService(Context.BATTERY_SERVICE) as BatteryManager
            val chargeCounter = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CHARGE_COUNTER)
            val capacity = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)

            val currentAvg = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_AVERAGE)
            val currentNow: Long =
                (mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_NOW) / 1000)

            Log.d(TAG, "chargeCounter $chargeCounter")
            Log.d(TAG, "capacity $capacity")
            Log.d(TAG, "CurrentAvg $currentAvg mah")
            Log.d(TAG, "currentNow $currentNow mah")

            return (chargeCounter.toFloat() / capacity.toFloat() * 100f).toLong()
        }

        return 0
    }


}

BatteryInfo.md

Recursos de los apuntes (Crear una app en Kotlin: Analizador de bateria)[ https://dev4phones.wordpress.com/2019/05/16/crear-una-app-paso-a-paso-usando-kotlin-en-android-studio-kotlin-battery-parte1/]

1 versión: valores directos

La primera versión es obteniendo los valores directos al detectar un cambio de la bateria

2 versión: Usando un objeto propio

La segunda versión es usando un objeto que almacene los valores al detectar un cambio de estado de la batería

• MainActivity2.kt
• BatteryInfo.kt

3 versió: Usando viewmodel (proximamente)

La tercer versión es implmentar el patrón viewmodel así al rotar el dispositivo no sea necesario desregistrar y registrar de nuevo la escucha del cambio de la batería, solo basta con suscribirse a la obtención de datos mediante un método del viewmodel

• MainActivity3.kt
• BatteryInfo.kt
• BatteryViewModel.kt

content_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"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        tools:showIn="@layout/activity_main"
        tools:context=".MainActivity"
        >

    <androidx.cardview.widget.CardView
            android:id="@+id/cardViewBatteryStatus"
            android:layout_gravity="center"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            app:cardCornerRadius="4dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            >

        <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                >

            <me.itangqi.waveloadingview.WaveLoadingView
                    android:id="@+id/batteryPercent"
                    android:layout_width="128dp"
                    android:layout_height="128dp"
                    app:wlv_borderColor="@color/colorAccent"
                    app:wlv_borderWidth="3dp"
                    app:wlv_progressValue="40"
                    app:wlv_shapeType="circle"
                    app:wlv_round_rectangle="true"
                    app:wlv_triangle_direction="north"
                    app:wlv_titleCenterStrokeColor="@android:color/holo_blue_dark"
                    app:wlv_titleCenterStrokeWidth="3dp"
                    app:wlv_titleCenter="30%"
                    app:wlv_titleCenterColor="@android:color/white"
                    app:wlv_titleCenterSize="24sp"
                    app:wlv_waveAmplitude="50"
                    app:layout_constraintTop_toTopOf="parent"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintBottom_toBottomOf="parent"
                    android:layout_marginBottom="8dp"
                    android:layout_marginStart="8dp"
                    android:layout_marginTop="8dp"
                    />

            <TextView
                    tools:text="Charging..."
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textAppearance="@style/TextAppearance.MaterialComponents.Headline6"
                    android:id="@+id/lblBatteryStatus"
                    app:layout_constraintStart_toEndOf="@+id/batteryPercent"
                    android:layout_marginStart="8dp"
                    app:layout_constraintEnd_toEndOf="parent"
                    android:layout_marginEnd="8dp"
                    android:layout_marginTop="8dp"
                    app:layout_constraintTop_toTopOf="parent"
                    app:layout_constraintHorizontal_bias="0.5"
                    app:layout_constraintBottom_toTopOf="@+id/lblBatteryCharge"
                    />

            <TextView
                    tools:text="usb charging"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textAppearance="@style/TextAppearance.MaterialComponents.Body2"
                    android:id="@+id/lblBatteryCharge"
                    android:layout_marginTop="8dp"
                    app:layout_constraintTop_toBottomOf="@+id/lblBatteryStatus"
                    app:layout_constraintStart_toEndOf="@+id/batteryPercent"
                    android:layout_marginStart="8dp"
                    app:layout_constraintEnd_toEndOf="parent"
                    android:layout_marginEnd="8dp"
                    app:layout_constraintHorizontal_bias="0.5"
                    app:layout_constraintBottom_toTopOf="@+id/lblBatteryHealth"
                    />

            <TextView
                    tools:text="goood"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textAppearance="@style/TextAppearance.MaterialComponents.Caption"
                    android:id="@+id/lblBatteryHealth"
                    app:layout_constraintTop_toBottomOf="@+id/lblBatteryCharge"
                    app:layout_constraintStart_toEndOf="@+id/batteryPercent"
                    android:layout_marginStart="8dp"
                    app:layout_constraintEnd_toEndOf="parent"
                    android:layout_marginEnd="8dp"
                    android:layout_marginTop="8dp"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintHorizontal_bias="0.5"
                    />

        </androidx.constraintlayout.widget.ConstraintLayout>
    </androidx.cardview.widget.CardView>

    <androidx.cardview.widget.CardView
            android:id="@+id/cardViewBatteryInfo"
            android:layout_gravity="center"
            android:layout_width="0dp"
            android:layout_height="0dp"
            app:cardCornerRadius="4dp"
            android:padding="8dp"
            android:layout_marginStart="8dp"
            app:layout_constraintTop_toBottomOf="@+id/cardViewBatteryStatus"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="8dp"
            android:layout_marginTop="16dp"
            android:layout_marginBottom="8dp"
            app:layout_constraintBottom_toBottomOf="parent"
            >

        <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                >

            <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="Battery info"
                    android:textAppearance="@style/TextAppearance.AppCompat.Large"
                    app:layout_constraintStart_toStartOf="parent"
                    android:layout_marginStart="8dp"
                    android:layout_marginTop="8dp"
                    app:layout_constraintTop_toTopOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    android:layout_marginEnd="8dp"
                    android:id="@+id/textView2"
                    />

            <TextView
                    android:id="@+id/outputText"
                    android:layout_width="0dp"
                    android:layout_height="0dp"
                    android:layout_marginTop="8dp"
                    tools:text="output text"
                    android:padding="8dp"
                    android:fontFamily="monospace"
                    android:background="@color/cardview_dark_background"
                    android:textColor="@color/md_grey_400"
                    app:layout_constraintTop_toBottomOf="@+id/textView2"
                    app:layout_constraintEnd_toEndOf="parent"
                    android:layout_marginEnd="8dp"
                    app:layout_constraintStart_toStartOf="parent"
                    android:layout_marginStart="8dp"
                    android:layout_marginBottom="8dp"
                    app:layout_constraintBottom_toBottomOf="parent"
                    />

        </androidx.constraintlayout.widget.ConstraintLayout>

    </androidx.cardview.widget.CardView>

</androidx.constraintlayout.widget.ConstraintLayout>

MAinActivity.kt

package com.example.batterycheck

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.BatteryManager
import android.os.Build
import android.os.Bundle
import android.util.Log
import android.view.Menu
import android.view.MenuItem
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.app.AppCompatDelegate
import androidx.core.content.ContextCompat
import com.google.android.material.snackbar.Snackbar
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.main.content_main.*
import kotlin.math.roundToInt

class MainActivity : AppCompatActivity() {

    companion object {
        val TAG: String = MainActivity::class.java.simpleName
    }

    //private lateinit var batteryPercent: WaveLoadingView


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)

        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)

        Log.d(TAG, "onCreate")

    }


    override fun onStart() {
        super.onStart()
        registerReceiver(batteryChangeReceiver, IntentFilter(Intent.ACTION_BATTERY_CHANGED))
    }

    override fun onStop() {
        super.onStop()
        unregisterReceiver(batteryChangeReceiver)
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        return when (item.itemId) {
            R.id.action_settings -> true
            else -> super.onOptionsItemSelected(item)
        }
    }


    fun isPlugged(context: Context): Boolean {
        val batteryStatus: Intent? = IntentFilter(Intent.ACTION_BATTERY_CHANGED).let { ifilter ->
            context.registerReceiver(null, ifilter)
        }

        //original
        val plugged: Int = batteryStatus?.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1) ?: -1
        return plugged == BatteryManager.BATTERY_PLUGGED_AC || plugged == BatteryManager.BATTERY_PLUGGED_USB || plugged == BatteryManager.BATTERY_PLUGGED_WIRELESS

    }

    private val batteryChangeReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context?, intent: Intent?) {

            Log.i(TAG, "onReceive $intent")

            /*when (intent?.action) {
                Intent.ACTION_POWER_CONNECTED -> handleSomethingHappened()
            }*/

            val status: Int? = intent?.getIntExtra(BatteryManager.EXTRA_STATUS, -1)
            val isCharging: Boolean = status == BatteryManager.BATTERY_STATUS_CHARGING
                    || status == BatteryManager.BATTERY_STATUS_FULL


            lblBatteryStatus.text = getBatteryStatusString(status)

            Log.d(TAG, "isCharging $isCharging")

            val chargePlug: Int? = intent?.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1)
            val isPlugged: Boolean = chargePlug == BatteryManager.BATTERY_PLUGGED_USB
                    || status == BatteryManager.BATTERY_PLUGGED_AC
                    || status == BatteryManager.BATTERY_PLUGGED_WIRELESS

            val usbCharge: Boolean = chargePlug == BatteryManager.BATTERY_PLUGGED_USB
            val acCharge: Boolean = chargePlug == BatteryManager.BATTERY_PLUGGED_AC
            val wirelessCharge: Boolean = chargePlug == BatteryManager.BATTERY_PLUGGED_WIRELESS

            when (chargePlug) {
                BatteryManager.BATTERY_PLUGGED_WIRELESS -> lblBatteryCharge.text =
                    getText(R.string.battery_plugged_wireless)
                BatteryManager.BATTERY_PLUGGED_AC -> lblBatteryCharge.text = getText(R.string.battery_plugged_ac)
                BatteryManager.BATTERY_PLUGGED_USB -> lblBatteryCharge.text = getText(R.string.battery_plugged_usb)
                else -> lblBatteryCharge.text = getText(R.string.battery_in_use)
            }

            val health: Int? = intent?.getIntExtra(BatteryManager.EXTRA_HEALTH, BatteryManager.BATTERY_HEALTH_UNKNOWN)
            lblBatteryHealth.text = getBatteryHealthString(health)

            val level: Int = intent!!.getIntExtra(BatteryManager.EXTRA_LEVEL, -1)
            val scale: Int = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
            val batteryPct: Float = level / scale.toFloat()

            Log.d(TAG, "batteryPct $batteryPct")

            batteryPercent.progressValue = (batteryPct * 100).roundToInt()
            batteryPercent.centerTitle = (batteryPct * 100).roundToInt().toString() + " %"
            batteryPercent.setAnimDuration(3000L)

            when ((batteryPct * 100).toInt()) {
                in 31..100 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_green_600)
                in 11..30 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_yellow_500)
                in 0..10 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_red_500)
            }


            val batteryVoltage: Int = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE, -1)
            val batteryTemperature: Int = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, -1)
            val batteryTechnology: String? = intent.getStringExtra(BatteryManager.EXTRA_TECHNOLOGY)

            Log.d(TAG, "battery voltage $batteryVoltage")
            Log.d(TAG, "battery temperature $batteryTemperature")
            Log.d(TAG, "battery technology $batteryTechnology")

            outputText.text = null

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_status_label).toString(),
                    getBatteryStatusString(status)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_plugged_label).toString(),
                    getBatteryPluggedString(chargePlug)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_level_label).toString(),
                    level
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_health_label).toString(),
                    getBatteryHealthString(health)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_voltage_label).toString(),
                    batteryVoltage
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_temperature_label).toString(),
                    (batteryTemperature / 10).toFloat()
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_technology_label).toString(),
                    batteryTechnology
                ) + System.getProperty("line.separator")
            )

        }

    }

    private fun getBatteryStatusString(status: Int?): String {
        return when (status) {
            BatteryManager.BATTERY_STATUS_CHARGING -> getText(R.string.battery_status_charging).toString()
            BatteryManager.BATTERY_STATUS_DISCHARGING -> getText(R.string.battery_status_discharging).toString()
            BatteryManager.BATTERY_STATUS_FULL -> getText(R.string.battery_status_full).toString()
            BatteryManager.BATTERY_STATUS_NOT_CHARGING -> getText(R.string.battery_status_not_charging).toString()
            BatteryManager.BATTERY_STATUS_UNKNOWN -> getText(R.string.battery_status_unknown).toString()
            else -> ""
        }
    }

    private fun getBatteryPluggedString(plugged: Int?): String {
        return when (plugged) {
            BatteryManager.BATTERY_PLUGGED_WIRELESS -> getText(R.string.battery_plugged_wireless).toString()
            BatteryManager.BATTERY_PLUGGED_AC -> getText(R.string.battery_plugged_ac).toString()
            BatteryManager.BATTERY_PLUGGED_USB -> getText(R.string.battery_plugged_usb).toString()
            else -> getText(R.string.battery_plugged_not).toString()
        }
    }

    private fun getBatteryHealthString(health: Int?): String {
        return when (health) {
            BatteryManager.BATTERY_HEALTH_GOOD -> getText(R.string.battery_health_good).toString()
            BatteryManager.BATTERY_HEALTH_COLD -> getText(R.string.battery_health_cold).toString()
            BatteryManager.BATTERY_HEALTH_DEAD -> getText(R.string.battery_health_dead).toString()
            BatteryManager.BATTERY_HEALTH_OVERHEAT -> getText(R.string.battery_health_overheat).toString()
            BatteryManager.BATTERY_HEALTH_OVER_VOLTAGE -> getText(R.string.battery_health_over_voltage).toString()
            BatteryManager.BATTERY_HEALTH_UNSPECIFIED_FAILURE -> getText(R.string.battery_health_unspecified_failure).toString()
            else -> getText(R.string.battery_health_unknown).toString()
        }
    }

    private fun getBatteryCapacity(ctx: Context): Long {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            val mBatteryManager = ctx.getSystemService(Context.BATTERY_SERVICE) as BatteryManager
            val chargeCounter = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CHARGE_COUNTER)
            val capacity = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)

            val currentAvg = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_AVERAGE)
            val currentNow: Long =
                (mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_NOW) / 1000)

            Log.d(TAG, "chargeCounter $chargeCounter")
            Log.d(TAG, "capacity $capacity")
            Log.d(TAG, "CurrentAvg $currentAvg mah")
            Log.d(TAG, "currentNow $currentNow mah")

            return (chargeCounter.toFloat() / capacity.toFloat() * 100f).toLong()
        }

        return 0
    }


}

MainActivity2.kt

package com.webserveis.batterycheck

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.BatteryManager
import android.os.Build
import android.os.Bundle
import android.util.Log
import android.view.Menu
import android.view.MenuItem
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.app.AppCompatDelegate
import androidx.core.content.ContextCompat
import com.google.android.material.snackbar.Snackbar
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.main.content_main.*
import kotlin.math.roundToInt


/*
https://www.baeldung.com/java-to-kotlin
adb shell dumpsys battery set level 30

https://danielme.com/2016/01/23/android-tutorial-broadcast-receiver/
https://github.com/BharathVishal/AndroidBatteryStats/blob/master/app/src/main/java/androidbatterystats/bharathvishal/com/androidbatterystats/MainActivity.kt
21> ACTION_POWER_SAVE_MODE_CHANGED
*/
class MainActivity : AppCompatActivity() {

    companion object {
        val TAG: String = MainActivity::class.java.simpleName
    }

    //private lateinit var batteryPercent: WaveLoadingView


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)

        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)

        Log.d(TAG, "onCreate")

        //batteryPercent = findViewById<WaveLoadingView>(R.id.batteryPercent)

        fab.setOnClickListener { view ->

            if (isPlugged(this)) {
                Toast.makeText(this@MainActivity, "plugged!", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this@MainActivity, "unplugged!", Toast.LENGTH_SHORT).show()
            }

            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                .setAction("Action", null).show()
        }
    }


    override fun onStart() {
        super.onStart()
        registerReceiver(batteryChangeReceiver, IntentFilter(Intent.ACTION_BATTERY_CHANGED))
    }

    override fun onStop() {
        super.onStop()
        unregisterReceiver(batteryChangeReceiver)
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        // Inflate the menu; this adds items to the action bar if it is present.
        menuInflater.inflate(R.menu.menu_main, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        return when (item.itemId) {
            R.id.action_battery_settings -> {
                val intentBatteryUsage = Intent(Intent.ACTION_POWER_USAGE_SUMMARY)
                startActivity(intentBatteryUsage)
                true
            }

            else -> super.onOptionsItemSelected(item)
        }
    }

    fun isPlugged(context: Context): Boolean {
        val batteryStatus: Intent? = IntentFilter(Intent.ACTION_BATTERY_CHANGED).let { ifilter ->
            context.registerReceiver(null, ifilter)
        }

        //original
        val plugged: Int = batteryStatus?.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1) ?: -1
        return plugged == BatteryManager.BATTERY_PLUGGED_AC || plugged == BatteryManager.BATTERY_PLUGGED_USB || plugged == BatteryManager.BATTERY_PLUGGED_WIRELESS

    }

    private val batteryChangeReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context?, intent: Intent?) {

            Log.i(TAG, "onReceive $intent")

            /*when (intent?.action) {
                Intent.ACTION_POWER_CONNECTED -> handleSomethingHappened()
            }*/

            val level: Int = intent!!.getIntExtra(BatteryManager.EXTRA_LEVEL, -1)
            val scale: Int = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
            val batteryPct: Float = level / scale.toFloat()

            val batteryInfo: BatteryInfo = BatteryInfo()
            batteryInfo.status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1)
            batteryInfo.level = batteryPct
            batteryInfo.chargePlug = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1)
            batteryInfo.health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH, BatteryManager.BATTERY_HEALTH_UNKNOWN)
            batteryInfo.voltage = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE, -1).toFloat()
            batteryInfo.temperature = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, -1)
            batteryInfo.technology = intent.getStringExtra(BatteryManager.EXTRA_TECHNOLOGY)

            Log.d(TAG, "batteryInfo $batteryInfo")

            lblBatteryStatus.text = getBatteryStatusString(batteryInfo.status)

            when (batteryInfo.chargePlug) {
                BatteryManager.BATTERY_PLUGGED_WIRELESS -> lblBatteryCharge.text =
                    getText(R.string.battery_plugged_wireless)
                BatteryManager.BATTERY_PLUGGED_AC -> lblBatteryCharge.text = getText(R.string.battery_plugged_ac)
                BatteryManager.BATTERY_PLUGGED_USB -> lblBatteryCharge.text = getText(R.string.battery_plugged_usb)
                else -> lblBatteryCharge.text = getText(R.string.battery_in_use)
            }

            lblBatteryHealth.text = getBatteryHealthString(batteryInfo.health)

            batteryPercent.progressValue = (batteryPct * 100).roundToInt()
            batteryPercent.centerTitle = (batteryPct * 100).roundToInt().toString() + " %"
            batteryPercent.setAnimDuration(3000L)

            when ((batteryPct * 100).toInt()) {
                in 31..100 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_green_600)
                in 11..30 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_yellow_500)
                in 0..10 -> batteryPercent.waveColor = ContextCompat.getColor(context!!, R.color.md_red_500)
            }


            outputText.text = null

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_status_label).toString(),
                    getBatteryStatusString(batteryInfo.status)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_plugged_label).toString(),
                    getBatteryPluggedString(batteryInfo.chargePlug)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_level_label).toString(),
                    level
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_health_label).toString(),
                    getBatteryHealthString(batteryInfo.health)
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_voltage_label).toString(),
                    batteryInfo.voltage
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_temperature_label).toString(),
                    (batteryInfo.temperature / 10).toFloat()
                ) + System.getProperty("line.separator")
            )

            outputText.append(
                String.format(
                    getText(R.string.battery_terminal_technology_label).toString(),
                    batteryInfo.technology
                ) + System.getProperty("line.separator")
            )

        }

    }

    private fun getBatteryStatusString(status: Int?): String {
        return when (status) {
            BatteryManager.BATTERY_STATUS_CHARGING -> getText(R.string.battery_status_charging).toString()
            BatteryManager.BATTERY_STATUS_DISCHARGING -> getText(R.string.battery_status_discharging).toString()
            BatteryManager.BATTERY_STATUS_FULL -> getText(R.string.battery_status_full).toString()
            BatteryManager.BATTERY_STATUS_NOT_CHARGING -> getText(R.string.battery_status_not_charging).toString()
            BatteryManager.BATTERY_STATUS_UNKNOWN -> getText(R.string.battery_status_unknown).toString()
            else -> ""
        }
    }

    private fun getBatteryPluggedString(plugged: Int?): String {
        return when (plugged) {
            BatteryManager.BATTERY_PLUGGED_WIRELESS -> getText(R.string.battery_plugged_wireless).toString()
            BatteryManager.BATTERY_PLUGGED_AC -> getText(R.string.battery_plugged_ac).toString()
            BatteryManager.BATTERY_PLUGGED_USB -> getText(R.string.battery_plugged_usb).toString()
            else -> getText(R.string.battery_plugged_not).toString()
        }
    }

    private fun getBatteryHealthString(health: Int?): String {
        return when (health) {
            BatteryManager.BATTERY_HEALTH_GOOD -> getText(R.string.battery_health_good).toString()
            BatteryManager.BATTERY_HEALTH_COLD -> getText(R.string.battery_health_cold).toString()
            BatteryManager.BATTERY_HEALTH_DEAD -> getText(R.string.battery_health_dead).toString()
            BatteryManager.BATTERY_HEALTH_OVERHEAT -> getText(R.string.battery_health_overheat).toString()
            BatteryManager.BATTERY_HEALTH_OVER_VOLTAGE -> getText(R.string.battery_health_over_voltage).toString()
            BatteryManager.BATTERY_HEALTH_UNSPECIFIED_FAILURE -> getText(R.string.battery_health_unspecified_failure).toString()
            else -> getText(R.string.battery_health_unknown).toString()
        }
    }

    private fun getBatteryCapacity(ctx: Context): Long {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            val mBatteryManager = ctx.getSystemService(Context.BATTERY_SERVICE) as BatteryManager
            val chargeCounter = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CHARGE_COUNTER)
            val capacity = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)

            val currentAvg = mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_AVERAGE)
            val currentNow: Long =
                (mBatteryManager.getLongProperty(BatteryManager.BATTERY_PROPERTY_CURRENT_NOW) / 1000)

            Log.d(TAG, "chargeCounter $chargeCounter")
            Log.d(TAG, "capacity $capacity")
            Log.d(TAG, "CurrentAvg $currentAvg mah")
            Log.d(TAG, "currentNow $currentNow mah")

            return (chargeCounter.toFloat() / capacity.toFloat() * 100f).toLong()
        }

        return 0
    }


}

strings.xml

<resources>
    <string name="app_name">Battery Check</string>
    <string name="action_settings">Settings</string>

    <string name="battery_status_charging">Charging</string>
    <string name="battery_status_discharging">Discharging</string>
    <string name="battery_status_full">Full</string>
    <string name="battery_status_not_charging">Not charging</string>
    <string name="battery_status_unknown">Unknown</string>

    <string name="battery_plugged_ac">Plugged AC</string>
    <string name="battery_plugged_usb">USB charge</string>
    <string name="battery_plugged_wireless">Wireless charge</string>
    <string name="battery_plugged_not">Not plugged</string>

    <string name="battery_in_use">Battery in use</string>

    <string name="battery_health_cold">Cold</string>
    <string name="battery_health_dead">Dead</string>
    <string name="battery_health_good">Good</string>
    <string name="battery_health_overheat">Overheat</string>
    <string name="battery_health_over_voltage">Over voltage</string>
    <string name="battery_health_unknown">Unknown</string>
    <string name="battery_health_unspecified_failure">Unspecified failure</string>

    <string name="battery_terminal_status_label">Status: %s</string>
    <string name="battery_terminal_plugged_label">Power plug: %s</string>
    <string name="battery_terminal_level_label">Level: %d%%</string>
    <string name="battery_terminal_health_label">Health: %s</string>
    <string name="battery_terminal_voltage_label">Current voltage: %d</string>
    <string name="battery_terminal_temperature_label">Temperature: %.1fºC</string>
    <string name="battery_terminal_technology_label">Technology: %s</string>
</resources>