Improved FilterOptionsDialog by changing the way it communicates with the DatePickerFragment, using an interface instead of a Handler.

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

@@ -4,8 +4,6 @@ package cy.agorise.bitsybitshareswallet.fragments
 import android.app.Dialog
 import android.content.res.Resources
 import android.os.Bundle
-import android.os.Handler
-import android.os.Message
 import android.view.View
 import androidx.fragment.app.DialogFragment
 import android.widget.*
@@ -32,15 +30,13 @@ import kotlin.collections.ArrayList
  * Creates a Dialog that communicates with {@link TransactionsActivity} to give it parameters about
  * how to filter the list of Transactions
  */
-class FilterOptionsDialog : DialogFragment() {
+class FilterOptionsDialog : DialogFragment(), DatePickerFragment.OnDateSetListener {
 
     companion object {
         private const val TAG = "FilterOptionsDialog"
 
         const val KEY_FILTER_OPTIONS = "key_filter_options"
 
-        const val KEY_TIMESTAMP = "key_timestamp"
-
         const val START_DATE_PICKER = 0
         const val END_DATE_PICKER = 1
     }
@@ -66,8 +62,6 @@ class FilterOptionsDialog : DialogFragment() {
 
     private var mCallback: OnFilterOptionsSelectedListener? = null
 
-    private lateinit var mDatePickerHandler: DatePickerHandler
-
     private var dateFormat: SimpleDateFormat = SimpleDateFormat("d/MMM/yyyy",
         ConfigurationCompat.getLocales(Resources.getSystem().configuration)[0])
 
@@ -79,17 +73,8 @@ class FilterOptionsDialog : DialogFragment() {
 
     private lateinit var mCurrency: Currency
 
-    /**
-     * DatePicker message handler.
-     */
-    inner class DatePickerHandler : Handler() {
-
-        override fun handleMessage(msg: Message) {
-            super.handleMessage(msg)
-            val bundle = msg.data
-            val timestamp = bundle.get(KEY_TIMESTAMP) as Long
-            //Log.d(TAG, "timestamp: $timestamp")
-            when (msg.arg1) {
+    override fun onDateSet(which: Int, timestamp: Long) {
+        when(which) {
             START_DATE_PICKER -> {
                 mFilterOptions.startDate = timestamp
 
@@ -112,7 +97,6 @@ class FilterOptionsDialog : DialogFragment() {
             }
         }
     }
-    }
 
     private fun updateDateTextViews() {
         var date = Date(mFilterOptions.startDate)
@@ -135,9 +119,6 @@ class FilterOptionsDialog : DialogFragment() {
 
         mFilterOptions = arguments?.getParcelable(KEY_FILTER_OPTIONS)!!
 
-        // Initialize handler for communication with the DatePicker
-        mDatePickerHandler = DatePickerHandler()
-
         val builder = AlertDialog.Builder(context!!)
             .setTitle(getString(R.string.title_filter_options))
             .setPositiveButton(getString(R.string.button__filter)) { _, _ ->  validateFields() }
@@ -266,9 +247,8 @@ class FilterOptionsDialog : DialogFragment() {
             currentTime = mFilterOptions.endDate
         }
 
-        val datePickerFragment = DatePickerFragment.newInstance(which, currentTime,
-            maxTime, mDatePickerHandler)
-        datePickerFragment.show(activity!!.supportFragmentManager, "date-picker")
+        val datePickerFragment = DatePickerFragment.newInstance(which, currentTime, maxTime)
+        datePickerFragment.show(childFragmentManager, "date-picker")
     }
 
     private fun validateFields() {

app/src/main/java/cy/agorise/bitsybitshareswallet/views/DatePickerFragment.kt

@@ -3,13 +3,16 @@ package cy.agorise.bitsybitshareswallet.views
 import android.app.DatePickerDialog
 import android.app.Dialog
 import android.os.Bundle
-import android.os.Message
 import android.widget.DatePicker
 import androidx.fragment.app.DialogFragment
+import androidx.fragment.app.Fragment
 import com.google.android.material.picker.MaterialDatePickerDialog
-import cy.agorise.bitsybitshareswallet.fragments.FilterOptionsDialog
 import java.util.*
 
+/**
+ * Lets the user select a Date and communicates the selection back to the parent fragment
+ * using the OnDateSetListener interface, which has to be implemented by the parent.
+ */
 class DatePickerFragment : DialogFragment(), DatePickerDialog.OnDateSetListener {
 
     companion object {
@@ -19,27 +22,23 @@ class DatePickerFragment : DialogFragment(), DatePickerDialog.OnDateSetListener
         const val KEY_CURRENT = "key_current"
         const val KEY_MAX = "key_max"
 
-        fun newInstance(
-            which: Int, currentTime: Long, maxTime: Long,
-            handler: FilterOptionsDialog.DatePickerHandler
-        ): DatePickerFragment {
+        fun newInstance(which: Int, currentTime: Long, maxTime: Long): DatePickerFragment {
             val f = DatePickerFragment()
             val bundle = Bundle()
             bundle.putInt(KEY_WHICH, which)
             bundle.putLong(KEY_CURRENT, currentTime)
             bundle.putLong(KEY_MAX, maxTime)
             f.arguments = bundle
-            f.setHandler(handler)
             return f
         }
     }
 
-    private var which: Int = 0
-    private var mHandler: FilterOptionsDialog.DatePickerHandler? = null
+    /**
+     * Callback used to communicate the date selection back to the parent
+     */
+    private var mCallback: OnDateSetListener? = null
 
-    fun setHandler(handler: FilterOptionsDialog.DatePickerHandler) {
-        mHandler = handler
-    }
+    private var which: Int = 0
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -47,6 +46,8 @@ class DatePickerFragment : DialogFragment(), DatePickerDialog.OnDateSetListener
     }
 
     override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
+        onAttachToParentFragment(parentFragment)
+
         val currentTime = arguments!!.getLong(KEY_CURRENT)
         val maxTime = arguments!!.getLong(KEY_MAX)
 
@@ -68,13 +69,25 @@ class DatePickerFragment : DialogFragment(), DatePickerDialog.OnDateSetListener
     }
 
     override fun onDateSet(view: DatePicker, year: Int, month: Int, day: Int) {
-        val msg = Message.obtain()
-        msg.arg1 = which
         val calendar = GregorianCalendar()
         calendar.set(year, month, day)
-        val bundle = Bundle()
-        bundle.putLong(FilterOptionsDialog.KEY_TIMESTAMP, calendar.time.time)
-        msg.data = bundle
-        mHandler!!.sendMessage(msg)
+        mCallback?.onDateSet(which, calendar.time.time)
+    }
+
+    /**
+     * Attaches the current [DialogFragment] to its [Fragment] parent, to initialize the
+     * [OnDateSetListener] interface
+     */
+    private fun onAttachToParentFragment(fragment: Fragment?) {
+        try {
+            mCallback = fragment as OnDateSetListener
+        } catch (e: ClassCastException) {
+            throw ClassCastException("$fragment must implement OnDateSetListener")
+        }
+    }
+
+    // Container Activity must implement this interface
+    interface OnDateSetListener {
+        fun onDateSet(which: Int, timestamp: Long)
     }
 }