Make use of Kotlin's null safe operations to avoid NullPointerException in various places in the app. Use of the ContextCompat and ConfigurationCompat classes in different screens to safely access app configuration and resources in a backwards compatible way.

app/src/main/java/cy/agorise/bitsybitshareswallet/adapters/TransfersDetailsAdapter.kt

@@ -9,6 +9,7 @@ import android.widget.LinearLayout
 import android.widget.TextView
 import androidx.constraintlayout.widget.ConstraintLayout
 import androidx.core.content.ContextCompat
+import androidx.core.os.ConfigurationCompat
 import androidx.navigation.findNavController
 import androidx.recyclerview.widget.RecyclerView
 import androidx.recyclerview.widget.SortedList
@@ -72,7 +73,7 @@ class TransfersDetailsAdapter(private val context: Context) :
     private val timeFormat: SimpleDateFormat
 
     init {
-        val locale = context.resources.configuration.locale
+        val locale = ConfigurationCompat.getLocales(context.resources.configuration)[0]
         dateFormat = SimpleDateFormat("dd MMM", locale)
         timeFormat = SimpleDateFormat("HH:mm:ss z", locale)
     }

app/src/main/java/cy/agorise/bitsybitshareswallet/fragments/BalancesFragment.kt

@@ -16,7 +16,6 @@ import cy.agorise.bitsybitshareswallet.viewmodels.BalanceDetailViewModel
 import kotlinx.android.synthetic.main.fragment_balances.*
 
 class BalancesFragment: Fragment() {
-    private val TAG = this.javaClass.simpleName
 
     private lateinit var mBalanceDetailViewModel: BalanceDetailViewModel
 
@@ -49,7 +48,7 @@ class BalancesFragment: Fragment() {
         super.setUserVisibleHint(isVisibleToUser)
         if (isVisibleToUser) {
             // TODO find a better way to recreate the fragment, that does it only when the theme has been changed
-            fragmentManager!!.beginTransaction().detach(this).attach(this).commit()
+            fragmentManager?.beginTransaction()?.detach(this)?.attach(this)?.commit()
         }
     }
 }

app/src/main/java/cy/agorise/bitsybitshareswallet/fragments/EReceiptFragment.kt

@@ -9,6 +9,7 @@ import android.text.Html
 import android.text.method.LinkMovementMethod
 import android.view.*
 import androidx.core.content.ContextCompat
+import androidx.core.os.ConfigurationCompat
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.Observer
 import androidx.lifecycle.ViewModelProviders
@@ -48,7 +49,7 @@ class EReceiptFragment : Fragment() {
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
-        mLocale = resources.configuration.locale
+        mLocale = ConfigurationCompat.getLocales(resources.configuration)[0]
 
         val userId = PreferenceManager.getDefaultSharedPreferences(context)
             .getString(Constants.KEY_CURRENT_ACCOUNT_ID, "") ?: ""
@@ -63,9 +64,9 @@ class EReceiptFragment : Fragment() {
     }
 
     private fun bindTransferDetail(transferDetail: TransferDetail) {
-        vPaymentDirection.setBackgroundColor(resources.getColor(
+        context?.let { vPaymentDirection.setBackgroundColor(ContextCompat.getColor(it,
             if(transferDetail.direction) R.color.colorReceive else R.color.colorSend
-        ))
+        ))}
 
         tvFrom.text = transferDetail.from ?: ""
         tvTo.text = transferDetail.to ?: ""

app/src/main/java/cy/agorise/bitsybitshareswallet/fragments/FilterOptionsDialog.kt

@@ -10,6 +10,7 @@ import android.view.View
 import androidx.fragment.app.DialogFragment
 import android.widget.*
 import androidx.appcompat.app.AlertDialog
+import androidx.core.os.ConfigurationCompat
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.ViewModelProviders
 import androidx.lifecycle.Observer
@@ -92,7 +93,7 @@ class FilterOptionsDialog : DialogFragment() {
     private lateinit var mDatePickerHandler: DatePickerHandler
 
     private var dateFormat: SimpleDateFormat = SimpleDateFormat("d/MMM/yyyy",
-        Resources.getSystem().configuration.locale)
+        ConfigurationCompat.getLocales(Resources.getSystem().configuration)[0])
 
     private var startDate: Long = 0
     private var endDate: Long = 0

app/src/main/java/cy/agorise/bitsybitshareswallet/fragments/HomeFragment.kt

@@ -19,8 +19,6 @@ import cy.agorise.bitsybitshareswallet.database.entities.UserAccount
 import cy.agorise.bitsybitshareswallet.utils.Constants
 import cy.agorise.bitsybitshareswallet.viewmodels.UserAccountViewModel
 import kotlinx.android.synthetic.main.fragment_home.*
-import android.os.Build
-import android.content.res.ColorStateList
 import androidx.appcompat.app.AppCompatActivity
 
 
@@ -112,10 +110,9 @@ class HomeFragment : Fragment() {
 
         var icon = tabLayout.getTabAt(2)?.icon
         if (icon != null) {
-            val colors: ColorStateList = if (Build.VERSION.SDK_INT >= 23) {
-                resources.getColorStateList(R.color.tab_icon_selector, context?.theme)
-            } else {
-                resources.getColorStateList(R.color.tab_icon_selector)
+            val colors = context?.let {context ->
+                ContextCompat.getColorStateList(
+                    context, R.color.tab_icon_selector)
             }
 
             icon = DrawableCompat.wrap(icon)

app/src/main/java/cy/agorise/bitsybitshareswallet/fragments/NetWorthFragment.kt

@@ -22,7 +22,7 @@ class NetWorthFragment: Fragment() {
         super.setUserVisibleHint(isVisibleToUser)
         if (isVisibleToUser) {
             // TODO find a better way to recreate the fragment, that does it only when the theme has been changed
-            fragmentManager!!.beginTransaction().detach(this).attach(this).commit()
+            fragmentManager?.beginTransaction()?.detach(this)?.attach(this)?.commit()
         }
     }
 }

app/src/main/java/cy/agorise/bitsybitshareswallet/fragments/ReceiveTransactionFragment.kt

@@ -325,10 +325,7 @@ class ReceiveTransactionFragment : ConnectedFragment() {
     }
 
     /**
-     * Updates the UI to show amount and account to send the payment
-     *
-     * @param total Total Amount in crypto to be paid
-     * @param account Account to pay total
+     * Updates the UI to show the amount and account to send the payment
      */
     private fun updateAmountAddressUI(assetAmount: Long, assetSymbol: String, assetPrecision: Int, account: String) {
         val txtAmount: String = if (assetAmount == 0L) {