Handle state saving in ConverterView

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

@@ -10,6 +10,7 @@ import com.simplemobiletools.calculator.databinding.ActivityUnitConverterBinding
 import com.simplemobiletools.calculator.extensions.config
 import com.simplemobiletools.calculator.extensions.updateViewColors
 import com.simplemobiletools.calculator.helpers.COMMA
+import com.simplemobiletools.calculator.helpers.CONVERTER_STATE
 import com.simplemobiletools.calculator.helpers.DOT
 import com.simplemobiletools.calculator.helpers.converters.Converter
 import com.simplemobiletools.commons.extensions.getProperTextColor
@@ -65,6 +66,12 @@ class UnitConverterActivity : SimpleActivity() {
 
         binding.viewUnitConverter.viewConverter.root.setConverter(converter)
         binding.unitConverterToolbar.setTitle(converter.nameResId)
+
+        if (savedInstanceState != null) {
+            savedInstanceState.getBundle(CONVERTER_STATE)?.also {
+                binding.viewUnitConverter.viewConverter.root.restoreFromSavedState(it)
+            }
+        }
     }
 
     private fun setupOptionsMenu() {
@@ -112,6 +119,11 @@ class UnitConverterActivity : SimpleActivity() {
         }
     }
 
+    override fun onSaveInstanceState(outState: Bundle) {
+        super.onSaveInstanceState(outState)
+        outState.putBundle(CONVERTER_STATE, binding.viewUnitConverter.viewConverter.root.saveState())
+    }
+
     private fun checkHaptic(view: View) {
         if (vibrateOnButtonPress) {
             view.performHapticFeedback()

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

@@ -30,6 +30,8 @@ const val COMMA = ","
 
 // shared prefs
 const val USE_COMMA_AS_DECIMAL_MARK = "use_comma_as_decimal_mark"
+
+// calculator state
 const val RES = "res"
 const val PREVIOUS_CALCULATION = "previousCalculation"
 const val LAST_KEY = "lastKey"
@@ -38,3 +40,9 @@ const val BASE_VALUE = "baseValue"
 const val SECOND_VALUE = "secondValue"
 const val INPUT_DISPLAYED_FORMULA = "inputDisplayedFormula"
 const val CALCULATOR_STATE = "calculatorState"
+
+// converter state
+const val TOP_UNIT = "top_unit"
+const val BOTTOM_UNIT = "bottom_unit"
+const val CONVERTER_VALUE = "converter_value"
+const val CONVERTER_STATE = "converter_state"

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

@@ -6,6 +6,7 @@ import android.content.res.ColorStateList
 import android.graphics.drawable.GradientDrawable
 import android.graphics.drawable.LayerDrawable
 import android.graphics.drawable.RippleDrawable
+import android.os.Bundle
 import android.util.AttributeSet
 import android.view.View
 import android.widget.LinearLayout
@@ -13,9 +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.helpers.COMMA
+import com.simplemobiletools.calculator.helpers.*
-import com.simplemobiletools.calculator.helpers.DOT
-import com.simplemobiletools.calculator.helpers.NumberFormatHelper
 import com.simplemobiletools.calculator.helpers.converters.Converter
 import com.simplemobiletools.commons.dialogs.RadioGroupDialog
 import com.simplemobiletools.commons.extensions.*
@@ -242,4 +241,19 @@ class ConverterView @JvmOverloads constructor(
             }
         }
     }
+
+    fun saveState(): Bundle = Bundle().apply {
+        putInt(TOP_UNIT, converter!!.units.indexOf(topUnit!!))
+        putInt(BOTTOM_UNIT, converter!!.units.indexOf(bottomUnit!!))
+        putString(CONVERTER_VALUE, binding.topUnitText.text.toString())
+    }
+
+    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)
+
+        updateBottomValue()
+        updateUnitLabelsAndSymbols()
+    }
 }