Merge pull request #327 from esensar/feature/unit-converter-remember-units

Store last selected units for each converter

app/src/main/kotlin/com/simplemobiletools/calculator/activities/UnitConverterActivity.kt

@@ -71,6 +71,11 @@ class UnitConverterActivity : SimpleActivity() {
             savedInstanceState.getBundle(CONVERTER_STATE)?.also {
                 binding.viewUnitConverter.viewConverter.root.restoreFromSavedState(it)
             }
+        } else {
+            val storedState = config.getLastConverterUnits(converter)
+            if (storedState != null) {
+                binding.viewUnitConverter.viewConverter.root.updateUnits(storedState.topUnit, storedState.bottomUnit)
+            }
         }
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/Config.kt

@@ -2,6 +2,8 @@ package com.simplemobiletools.calculator.helpers
 
 import android.content.Context
 import com.simplemobiletools.calculator.extensions.sharedPreferencesCallback
+import com.simplemobiletools.calculator.helpers.converters.Converter
+import com.simplemobiletools.calculator.models.ConverterUnitsState
 import com.simplemobiletools.commons.helpers.BaseConfig
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.filterNotNull
@@ -15,6 +17,26 @@ class Config(context: Context) : BaseConfig(context) {
         get() = prefs.getBoolean(USE_COMMA_AS_DECIMAL_MARK, getDecimalSeparator() == COMMA)
         set(useCommaAsDecimalMark) = prefs.edit().putBoolean(USE_COMMA_AS_DECIMAL_MARK, useCommaAsDecimalMark).apply()
 
+    fun getLastConverterUnits(converter: Converter): ConverterUnitsState? {
+        val storedState = prefs.getString("$CONVERTER_UNITS_PREFIX.${converter.key}", null)
+        return if (!storedState.isNullOrEmpty()) {
+            val parts = storedState.split(",").map { part ->
+                converter.units.first { it.key == part }
+            }
+            if (parts.size == 2) {
+                ConverterUnitsState(parts[0], parts[1])
+            } else {
+                null
+            }
+        } else {
+            null
+        }
+    }
+
+    fun putLastConverterUnits(converter: Converter, topUnit: Converter.Unit, bottomUnit: Converter.Unit) {
+        prefs.edit().putString("$CONVERTER_UNITS_PREFIX.${converter.key}", "${topUnit.key},${bottomUnit.key}").apply()
+    }
+
     val preventPhoneFromSleepingFlow: Flow<Boolean> = prefs.run { sharedPreferencesCallback { preventPhoneFromSleeping } }.filterNotNull()
     val vibrateOnButtonPressFlow: Flow<Boolean> = prefs.run { sharedPreferencesCallback { vibrateOnButtonPress } }.filterNotNull()
     val wasUseEnglishToggledFlow: Flow<Boolean> = prefs.run { sharedPreferencesCallback { wasUseEnglishToggled } }.filterNotNull()

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/Constants.kt

@@ -30,6 +30,7 @@ const val COMMA = ","
 
 // shared prefs
 const val USE_COMMA_AS_DECIMAL_MARK = "use_comma_as_decimal_mark"
+const val CONVERTER_UNITS_PREFIX = "converter_last_units"
 
 // calculator state
 const val RES = "res"

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/AreaConverter.kt

@@ -5,66 +5,77 @@ import com.simplemobiletools.calculator.R
 object AreaConverter : Converter {
     override val nameResId: Int = R.string.unit_area
     override val imageResId: Int = R.drawable.ic_box_vector
+    override val key: String = "AreaConverter"
 
-    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double) : Converter.Unit(nameResId, symbolResId, factor) {
+    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double, key: String) : Converter.Unit(nameResId, symbolResId, factor, key) {
         data object SquareKilometer : Unit(
             nameResId = R.string.unit_area_square_kilometer,
             symbolResId = R.string.unit_area_square_kilometer_symbol,
-            factor = 1000000.0
+            factor = 1000000.0,
+            key = "SquareKilometer"
         )
 
         data object SquareMeter : Unit(
             nameResId = R.string.unit_area_square_meter,
             symbolResId = R.string.unit_area_square_meter_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "SquareMeter"
         )
 
         data object SquareCentimeter : Unit(
             nameResId = R.string.unit_area_square_centimeter,
             symbolResId = R.string.unit_area_square_centimeter_symbol,
-            factor = 0.0001
+            factor = 0.0001,
+            key = "SquareCentimeter"
         )
 
         data object SquareMillimeter : Unit(
             nameResId = R.string.unit_area_square_millimeter,
             symbolResId = R.string.unit_area_square_millimeter_symbol,
-            factor = 0.000001
+            factor = 0.000001,
+            key = "SquareMillimeter"
         )
 
         data object SquareMile : Unit(
             nameResId = R.string.unit_area_square_mile,
             symbolResId = R.string.unit_area_square_mile_symbol,
-            factor = 2_589_988.110336
+            factor = 2_589_988.110336,
+            key = "SquareMile"
         )
 
         data object SquareYard : Unit(
             nameResId = R.string.unit_area_square_yard,
             symbolResId = R.string.unit_area_square_yard_symbol,
-            factor = 0.83612736
+            factor = 0.83612736,
+            key = "SquareYard"
         )
 
         data object SquareFoot : Unit(
             nameResId = R.string.unit_area_square_foot,
             symbolResId = R.string.unit_area_square_foot_symbol,
-            factor = 0.09290304
+            factor = 0.09290304,
+            key = "SquareFoot"
         )
 
         data object SquareInch : Unit(
             nameResId = R.string.unit_area_square_inch,
             symbolResId = R.string.unit_area_square_inch_symbol,
-            factor = 0.00064516
+            factor = 0.00064516,
+            key = "SquareInch"
         )
 
         data object Acre : Unit(
             nameResId = R.string.unit_area_acre,
             symbolResId = R.string.unit_area_acre_symbol,
-            factor = 4_046.8564224
+            factor = 4_046.8564224,
+            key = "Acre"
         )
 
         data object Hectare : Unit(
             nameResId = R.string.unit_area_hectare,
             symbolResId = R.string.unit_area_hectare_symbol,
-            factor = 10_000.0
+            factor = 10_000.0,
+            key = "Hectare"
         )
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/Base.kt

@@ -21,6 +21,8 @@ interface Converter {
     val defaultTopUnit: Unit
     val defaultBottomUnit: Unit
 
+    val key: String
+
     fun convert(from: ValueWithUnit<Unit>, to: Unit): ValueWithUnit<Unit> {
         return ValueWithUnit(to.fromBase(from.unit.toBase(from.value)), to)
     }
@@ -28,7 +30,8 @@ interface Converter {
     open class Unit(
         val nameResId: Int,
         val symbolResId: Int,
-        val factor: Double
+        val factor: Double,
+        val key: String
     ) {
 
         open fun toBase(value: Double) = value * factor

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/LengthConverter.kt

@@ -5,102 +5,119 @@ import com.simplemobiletools.calculator.R
 object LengthConverter : Converter {
     override val nameResId: Int = R.string.unit_length
     override val imageResId: Int = R.drawable.ic_height_vector
+    override val key: String = "LengthConverter"
 
-    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double) : Converter.Unit(nameResId, symbolResId, factor) {
+    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double, key: String) : Converter.Unit(nameResId, symbolResId, factor, key) {
         data object Kilometer : Unit(
             nameResId = R.string.unit_length_kilometer,
             symbolResId = R.string.unit_length_kilometer_symbol,
-            factor = 1000.0
+            factor = 1000.0,
+            key = "Kilometer"
         )
 
         data object Meter : Unit(
             nameResId = R.string.unit_length_meter,
             symbolResId = R.string.unit_length_meter_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "Meter"
         )
 
         data object Centimeter : Unit(
             nameResId = R.string.unit_length_centimeter,
             symbolResId = R.string.unit_length_centimeter_symbol,
-            factor = 0.01
+            factor = 0.01,
+            key = "Centimeter"
         )
 
         data object Millimeter : Unit(
             nameResId = R.string.unit_length_millimeter,
             symbolResId = R.string.unit_length_millimeter_symbol,
-            factor = 0.001
+            factor = 0.001,
+            key = "Millimeter"
         )
 
         data object Micrometer : Unit(
             nameResId = R.string.unit_length_micrometer,
             symbolResId = R.string.unit_length_micrometer_symbol,
-            factor = 0.000001
+            factor = 0.000001,
+            key = "Micrometer"
         )
 
         data object Nanometer : Unit(
             nameResId = R.string.unit_length_nanometer,
             symbolResId = R.string.unit_length_nanometer_symbol,
-            factor = 0.000000001
+            factor = 0.000000001,
+            key = "Nanometer"
         )
 
         data object Angstrom : Unit(
             nameResId = R.string.unit_length_angstrom,
             symbolResId = R.string.unit_length_angstrom_symbol,
-            factor = 1e-10
+            factor = 1e-10,
+            key = "Angstrom"
         )
 
         data object Mile : Unit(
             nameResId = R.string.unit_length_mile,
             symbolResId = R.string.unit_length_mile_symbol,
-            factor = 1_609.344
+            factor = 1_609.344,
+            key = "Mile"
         )
 
         data object Yard : Unit(
             nameResId = R.string.unit_length_yard,
             symbolResId = R.string.unit_length_yard_symbol,
-            factor = 0.9144
+            factor = 0.9144,
+            key = "Yard"
         )
 
         data object Foot : Unit(
             nameResId = R.string.unit_length_foot,
             symbolResId = R.string.unit_length_foot_symbol,
-            factor = 0.3048
+            factor = 0.3048,
+            key = "Foot"
         )
 
         data object Inch : Unit(
             nameResId = R.string.unit_length_inch,
             symbolResId = R.string.unit_length_inch_symbol,
-            factor = 0.0254
+            factor = 0.0254,
+            key = "Inch"
         )
 
         data object Fathom : Unit(
             nameResId = R.string.unit_length_fathom,
             symbolResId = R.string.unit_length_fathom_symbol,
-            factor = 1.852
+            factor = 1.852,
+            key = "Fathom"
         )
 
         data object NauticalMile : Unit(
             nameResId = R.string.unit_length_nautical_mile,
             symbolResId = R.string.unit_length_nautical_mile_symbol,
-            factor = 1_852.0
+            factor = 1_852.0,
+            key = "NauticalMile"
         )
 
         data object AstronomicalUnit : Unit(
             nameResId = R.string.unit_length_astronomical_unit,
             symbolResId = R.string.unit_length_astronomical_unit_symbol,
-            factor = 1.495979e+11
+            factor = 1.495979e+11,
+            key = "AstronomicalUnit"
         )
 
         data object Parsec : Unit(
             nameResId = R.string.unit_length_parsec,
             symbolResId = R.string.unit_length_parsec_symbol,
-            factor = 3.0857e+16
+            factor = 3.0857e+16,
+            key = "Parsec"
         )
 
         data object LightYear : Unit(
             nameResId = R.string.unit_length_light_year,
             symbolResId = R.string.unit_length_light_year_symbol,
-            factor = 9.4607e+15
+            factor = 9.4607e+15,
+            key = "LightYear"
         )
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/MassConverter.kt

@@ -5,90 +5,105 @@ import com.simplemobiletools.calculator.R
 object MassConverter : Converter {
     override val nameResId: Int = R.string.unit_mass
     override val imageResId: Int = R.drawable.ic_scale_vector
+    override val key: String = "MassConverter"
 
-    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double) : Converter.Unit(nameResId, symbolResId, factor) {
+    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double, key: String) : Converter.Unit(nameResId, symbolResId, factor, key) {
         data object Gram : Unit(
             nameResId = R.string.unit_mass_gram,
             symbolResId = R.string.unit_mass_gram_symbol,
-            factor = 0.001
+            factor = 0.001,
+            key = "Gram"
         )
 
         data object Kilogram : Unit(
             nameResId = R.string.unit_mass_kilogram,
             symbolResId = R.string.unit_mass_kilogram_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "Kilogram"
         )
 
         data object Milligram : Unit(
             nameResId = R.string.unit_mass_milligram,
             symbolResId = R.string.unit_mass_milligram_symbol,
-            factor = 0.000001
+            factor = 0.000001,
+            key = "Milligram"
         )
 
         data object Microgram : Unit(
             nameResId = R.string.unit_mass_microgram,
             symbolResId = R.string.unit_mass_microgram_symbol,
-            factor = 0.000000001
+            factor = 0.000000001,
+            key = "Microgram"
         )
 
         data object Tonne : Unit(
             nameResId = R.string.unit_mass_tonne,
             symbolResId = R.string.unit_mass_tonne_symbol,
-            factor = 1_000.0
+            factor = 1_000.0,
+            key = "Tonne"
         )
 
         data object Pound : Unit(
             nameResId = R.string.unit_mass_pound,
             symbolResId = R.string.unit_mass_pound_symbol,
-            factor = 0.45359237
+            factor = 0.45359237,
+            key = "Pound"
         )
 
         data object Ounce : Unit(
             nameResId = R.string.unit_mass_ounce,
             symbolResId = R.string.unit_mass_ounce_symbol,
-            factor = 0.028349523125
+            factor = 0.028349523125,
+            key = "Ounce"
         )
 
         data object Grain : Unit(
             nameResId = R.string.unit_mass_grain,
             symbolResId = R.string.unit_mass_grain_symbol,
-            factor = 0.00006479891
+            factor = 0.00006479891,
+            key = "Grain"
         )
 
         data object Dram : Unit(
             nameResId = R.string.unit_mass_dram,
             symbolResId = R.string.unit_mass_dram_symbol,
-            factor = 0.0017718451953125
+            factor = 0.0017718451953125,
+            key = "Dram"
         )
 
         data object Stone : Unit(
             nameResId = R.string.unit_mass_stone,
             symbolResId = R.string.unit_mass_stone_symbol,
-            factor = 6.35029318
+            factor = 6.35029318,
+            key = "Stone"
         )
 
         data object LongTon : Unit(
             nameResId = R.string.unit_mass_long_ton,
             symbolResId = R.string.unit_mass_long_ton_symbol,
-            factor = 1_016.0469088
+            factor = 1_016.0469088,
+            key = "LongTon"
         )
 
         data object ShortTon : Unit(
             nameResId = R.string.unit_mass_short_ton,
             symbolResId = R.string.unit_mass_short_ton_symbol,
-            factor = 907.18474
+            factor = 907.18474,
+            key = "ShortTon"
         )
 
         data object Carat : Unit(
             nameResId = R.string.unit_mass_carat,
             symbolResId = R.string.unit_mass_carat_symbol,
-            factor = 0.0002051965483
+            factor = 0.0002051965483,
+            key = "Carat"
         )
 
         data object CaratMetric : Unit(
             nameResId = R.string.unit_mass_carat_metric,
             symbolResId = R.string.unit_mass_carat_metric_symbol,
-            factor = 0.0002
+            factor = 0.0002,
+            key = "CaratMetric"
         )
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/TemperatureConverter.kt

@@ -5,13 +5,15 @@ import com.simplemobiletools.calculator.R
 object TemperatureConverter : Converter {
     override val nameResId: Int = R.string.unit_temperature
     override val imageResId: Int = R.drawable.ic_thermostat_vector
+    override val key: String = "TemperatureConverter"
 
-    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double) : Converter.Unit(nameResId, symbolResId, factor) {
+    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double, key: String) : Converter.Unit(nameResId, symbolResId, factor, key) {
 
         data object Celsius : Unit(
             nameResId = R.string.unit_temperature_celsius,
             symbolResId = R.string.unit_temperature_celsius_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "Celsius"
         ) {
             const val KELVIN_OFFSET = 273.15
 
@@ -22,7 +24,8 @@ object TemperatureConverter : Converter {
         data object Fahrenheit : Unit(
             nameResId = R.string.unit_temperature_fahrenheit,
             symbolResId = R.string.unit_temperature_fahrenheit_symbol,
-            factor = 9.0 / 5
+            factor = 9.0 / 5,
+            key = "Fahrenheit"
         ) {
             private const val CELSIUS_OFFSET = 32
 
@@ -34,13 +37,15 @@ object TemperatureConverter : Converter {
         data object Rankine : Unit(
             nameResId = R.string.unit_temperature_rankine,
             symbolResId = R.string.unit_temperature_rankine_symbol,
-            factor = 5.0 / 9
+            factor = 5.0 / 9,
+            key = "Rankine"
         )
 
         data object Kelvin : Unit(
             nameResId = R.string.unit_temperature_kelvin,
             symbolResId = R.string.unit_temperature_kelvin_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "Kelvin"
         )
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/TimeConverter.kt

@@ -5,8 +5,9 @@ import com.simplemobiletools.calculator.R
 object TimeConverter : Converter {
     override val nameResId: Int = R.string.unit_time
     override val imageResId: Int = com.simplemobiletools.commons.R.drawable.ic_clock_vector
+    override val key: String = "TimeConverter"
 
-    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double) : Converter.Unit(nameResId, symbolResId, factor) {
+    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double, key: String) : Converter.Unit(nameResId, symbolResId, factor, key) {
         companion object {
             private const val MINUTE = 60.0
             private const val HOUR = 60.0 * MINUTE
@@ -17,43 +18,50 @@ object TimeConverter : Converter {
         data object Hour : Unit(
             nameResId = R.string.unit_time_hour,
             symbolResId = R.string.unit_time_hour_symbol,
-            factor = HOUR
+            factor = HOUR,
+            key = "Hour"
         )
 
         data object Minute : Unit(
             nameResId = R.string.unit_time_minute,
             symbolResId = R.string.unit_time_minute_symbol,
-            factor = MINUTE
+            factor = MINUTE,
+            key = "Minute"
         )
 
         data object Second : Unit(
             nameResId = R.string.unit_time_second,
             symbolResId = R.string.unit_time_second_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "Second"
         )
 
         data object Millisecond : Unit(
             nameResId = R.string.unit_time_millisecond,
             symbolResId = R.string.unit_time_millisecond_symbol,
-            factor = 0.001
+            factor = 0.001,
+            key = "Millisecond"
         )
 
         data object Day : Unit(
             nameResId = R.string.unit_time_day,
             symbolResId = R.string.unit_time_day_symbol,
-            factor = DAY
+            factor = DAY,
+            key = "Day"
         )
 
         data object Week : Unit(
             nameResId = R.string.unit_time_week,
             symbolResId = R.string.unit_time_week_symbol,
-            factor = DAY * 7
+            factor = DAY * 7,
+            key = "Week"
         )
 
         data object Year : Unit(
             nameResId = R.string.unit_time_year,
             symbolResId = R.string.unit_time_year_symbol,
-            factor = GREGORIAN_YEAR
+            factor = GREGORIAN_YEAR,
+            key = "Year"
         )
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/converters/VolumeConverter.kt

@@ -5,144 +5,168 @@ import com.simplemobiletools.calculator.R
 object VolumeConverter : Converter {
     override val nameResId: Int = R.string.unit_volume
     override val imageResId: Int = R.drawable.ic_drop_vector
+    override val key: String = "VolumeConverter"
 
-    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double) : Converter.Unit(nameResId, symbolResId, factor) {
+    sealed class Unit(nameResId: Int, symbolResId: Int, factor: Double, key: String) : Converter.Unit(nameResId, symbolResId, factor, key) {
         data object CubicMeter : Unit(
             nameResId = R.string.unit_volume_cubic_meter,
             symbolResId = R.string.unit_volume_cubic_meter_symbol,
-            factor = 1.0
+            factor = 1.0,
+            key = "CubicMeter"
         )
 
         data object CubicDecimeter : Unit(
             nameResId = R.string.unit_volume_cubic_decimeter,
             symbolResId = R.string.unit_volume_cubic_decimeter_symbol,
-            factor = 0.001
+            factor = 0.001,
+            key = "CubicDecimeter"
         )
 
         data object CubicCentimeter : Unit(
             nameResId = R.string.unit_volume_cubic_centimeter,
             symbolResId = R.string.unit_volume_cubic_centimeter_symbol,
-            factor = 0.000001
+            factor = 0.000001,
+            key = "CubicCentimeter"
         )
 
         data object CubicMillimeter : Unit(
             nameResId = R.string.unit_volume_cubic_millimeter,
             symbolResId = R.string.unit_volume_cubic_millimeter_symbol,
-            factor = 0.000000001
+            factor = 0.000000001,
+            key = "CubicMillimeter"
         )
 
         data object Liter : Unit(
             nameResId = R.string.unit_volume_liter,
             symbolResId = R.string.unit_volume_liter_symbol,
-            factor = 0.001
+            factor = 0.001,
+            key = "Liter"
         )
 
         data object Centiliter : Unit(
             nameResId = R.string.unit_volume_centiliter,
             symbolResId = R.string.unit_volume_centiliter_symbol,
-            factor = 0.0001
+            factor = 0.0001,
+            key = "Centiliter"
         )
 
         data object Deciliter : Unit(
             nameResId = R.string.unit_volume_deciliter,
             symbolResId = R.string.unit_volume_deciliter_symbol,
-            factor = 0.00001
+            factor = 0.00001,
+            key = "Deciliter"
         )
 
         data object Milliliter : Unit(
             nameResId = R.string.unit_volume_milliliter,
             symbolResId = R.string.unit_volume_milliliter_symbol,
-            factor = 0.000001
+            factor = 0.000001,
+            key = "Milliliter"
         )
 
         data object AcreFoot : Unit(
             nameResId = R.string.unit_volume_acre_foot,
             symbolResId = R.string.unit_volume_acre_foot_symbol,
-            factor = 1_233.48183754752
+            factor = 1_233.48183754752,
+            key = "AcreFoot"
         )
 
         data object CubicFoot : Unit(
             nameResId = R.string.unit_volume_cubic_foot,
             symbolResId = R.string.unit_volume_cubic_foot_symbol,
-            factor = 0.028316846592
+            factor = 0.028316846592,
+            key = "CubicFoot"
         )
 
         data object CubicInch : Unit(
             nameResId = R.string.unit_volume_cubic_inch,
             symbolResId = R.string.unit_volume_cubic_inch_symbol,
-            factor = 0.000016387064
+            factor = 0.000016387064,
+            key = "CubicInch"
         )
 
         data object BarrelUS : Unit(
             nameResId = R.string.unit_volume_barrel_us,
             symbolResId = R.string.unit_volume_barrel_us_symbol,
-            factor = 0.119240471196
+            factor = 0.119240471196,
+            key = "BarrelUS"
         )
 
         data object GallonUS : Unit(
             nameResId = R.string.unit_volume_gallon_us,
             symbolResId = R.string.unit_volume_gallon_us_symbol,
-            factor = 0.003785411784
+            factor = 0.003785411784,
+            key = "GallonUS"
         )
 
         data object QuartUS : Unit(
             nameResId = R.string.unit_volume_quart_us,
             symbolResId = R.string.unit_volume_quart_us_symbol,
-            factor = 0.000946352946
+            factor = 0.000946352946,
+            key = "QuartUS"
         )
 
         data object PintUS : Unit(
             nameResId = R.string.unit_volume_pint_us,
             symbolResId = R.string.unit_volume_pint_us_symbol,
-            factor = 0.000473176473
+            factor = 0.000473176473,
+            key = "PintUS"
         )
 
         data object GillUS : Unit(
             nameResId = R.string.unit_volume_gill_us,
             symbolResId = R.string.unit_volume_gill_us_symbol,
-            factor = 0.00011829411825
+            factor = 0.00011829411825,
+            key = "GillUS"
         )
 
         data object FluidOunceUS : Unit(
             nameResId = R.string.unit_volume_fluid_ounce_us,
             symbolResId = R.string.unit_volume_fluid_ounce_us_symbol,
-            factor = 0.00003
+            factor = 0.00003,
+            key = "FluidOunceUS"
         )
 
         data object BarrelImperial : Unit(
             nameResId = R.string.unit_volume_barrel_imperial,
             symbolResId = R.string.unit_volume_barrel_imperial_symbol,
-            factor = 0.16365924
+            factor = 0.16365924,
+            key = "BarrelImperial"
         )
 
         data object GallonImperial : Unit(
             nameResId = R.string.unit_volume_gallon_imperial,
             symbolResId = R.string.unit_volume_gallon_imperial_symbol,
-            factor = 0.00454609
+            factor = 0.00454609,
+            key = "GallonImperial"
         )
 
         data object QuartImperial : Unit(
             nameResId = R.string.unit_volume_quart_imperial,
             symbolResId = R.string.unit_volume_quart_imperial_symbol,
-            factor = 0.0011365225
+            factor = 0.0011365225,
+            key = "QuartImperial"
         )
 
         data object PintImperial : Unit(
             nameResId = R.string.unit_volume_pint_imperial,
             symbolResId = R.string.unit_volume_pint_imperial_symbol,
-            factor = 0.00056826125
+            factor = 0.00056826125,
+            key = "PintImperial"
         )
 
         data object GillImperial : Unit(
             nameResId = R.string.unit_volume_gill_imperial,
             symbolResId = R.string.unit_volume_gill_imperial_symbol,
-            factor = 0.0001420653125
+            factor = 0.0001420653125,
+            key = "GillImperial"
         )
 
         data object FluidOunceImperial : Unit(
             nameResId = R.string.unit_volume_fluid_ounce_imperial,
             symbolResId = R.string.unit_volume_fluid_ounce_imperial_symbol,
-            factor = 0.0000284130625
+            factor = 0.0000284130625,
+            key = "FluidOunceImperial"
         )
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/models/ConverterUnitsState.kt

@@ -0,0 +1,8 @@
+package com.simplemobiletools.calculator.models
+
+import com.simplemobiletools.calculator.helpers.converters.Converter
+
+data class ConverterUnitsState(
+    val topUnit: Converter.Unit,
+    val bottomUnit: Converter.Unit,
+)

app/src/main/kotlin/com/simplemobiletools/calculator/views/ConverterView.kt

@@ -14,6 +14,7 @@ import androidx.core.content.res.ResourcesCompat
 import androidx.core.widget.TextViewCompat
 import com.simplemobiletools.calculator.R
 import com.simplemobiletools.calculator.databinding.ViewConverterBinding
+import com.simplemobiletools.calculator.extensions.config
 import com.simplemobiletools.calculator.helpers.*
 import com.simplemobiletools.calculator.helpers.converters.Converter
 import com.simplemobiletools.commons.dialogs.RadioGroupDialog
@@ -243,6 +244,7 @@ class ConverterView @JvmOverloads constructor(
                     updateBottomValue()
                 }
                 updateUnitLabelsAndSymbols()
+                context.config.putLastConverterUnits(converter!!, topUnit!!, bottomUnit!!)
             }
         }
     }
@@ -254,9 +256,15 @@ class ConverterView @JvmOverloads constructor(
     }
 
     fun restoreFromSavedState(state: Bundle) {
-        topUnit = converter!!.units[state.getInt(TOP_UNIT)]
-        bottomUnit = converter!!.units[state.getInt(BOTTOM_UNIT)]
         binding.topUnitText.text = state.getString(CONVERTER_VALUE)
+        val storedTopUnit = converter!!.units[state.getInt(TOP_UNIT)]
+        val storedBottomUnit = converter!!.units[state.getInt(BOTTOM_UNIT)]
+        updateUnits(storedTopUnit, storedBottomUnit)
+    }
+
+    fun updateUnits(newTopUnit: Converter.Unit, newBottomUnit: Converter.Unit) {
+        topUnit = newTopUnit
+        bottomUnit = newBottomUnit
 
         updateBottomValue()
         updateUnitLabelsAndSymbols()