Improve handling of 12/24 hour timestamps on configuration change.

This fixes an edge case seen on ConversationFragment, where if the
device time format is switched between 12/24 hour format while the app
is running, the old time format will still be displayed when the app
is resumed.

This is due to a design flaw in `DateTimeFormatter.ofLocalizedTime`,
where the time format is statically cached and not updated upon
configuration change. The `LocalTime.formatHours()` extension method
was updated to no longer rely on the misbehaving `ofLocalTime` method.

In addition, `ConversationMessaageComputeWorkers.recomputeFormattedDate`
was designed to skip recomputing non-relative timestamps. This works
in most cases but not this specific edge case. A `force: Boolean` flag
was added to force all items to be updated. And the `force = true` flag
was passed upon `onResume` of the fragment.

Closes #14121

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationFragment.kt

@@ -665,6 +665,11 @@ class ConversationFragment :
     outState.putBoolean(SAVED_STATE_IS_SEARCH_REQUESTED, isSearchRequested)
   }
 
+  override fun onStart() {
+    super.onStart()
+    recomputeMessageDates(forceUpdate = true)
+  }
+
   override fun onResume() {
     super.onResume()
 
@@ -1173,12 +1178,7 @@ class ConversationFragment :
 
     getVoiceNoteMediaController().voiceNotePlaybackState.observe(viewLifecycleOwner, inputPanel.playbackStateObserver)
 
-    val conversationUpdateTick = ConversationUpdateTick {
-      disposables += ConversationMessageComputeWorkers.recomputeFormattedDate(
-        requireContext(),
-        adapter.currentList.filterIsInstance<ConversationMessageElement>()
-      ).observeOn(AndroidSchedulers.mainThread()).subscribeBy { adapter.updateTimestamps() }
-    }
+    val conversationUpdateTick = ConversationUpdateTick { recomputeMessageDates() }
 
     viewLifecycleOwner.lifecycle.addObserver(conversationUpdateTick)
 
@@ -1188,6 +1188,17 @@ class ConversationFragment :
     }
   }
 
+  private fun recomputeMessageDates(forceUpdate: Boolean = false) {
+    disposables += ConversationMessageComputeWorkers
+      .recomputeFormattedDate(
+        context = requireContext(),
+        items = adapter.currentList.filterIsInstance<ConversationMessageElement>(),
+        forceUpdate = forceUpdate
+      )
+      .observeOn(AndroidSchedulers.mainThread())
+      .subscribeBy { adapter.updateTimestamps() }
+  }
+
   private fun initializeInlineSearch() {
     inlineQueryController.onOrientationChange(resources.configuration.orientation == Configuration.ORIENTATION_LANDSCAPE)
 

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/computed/ConversationMessageComputeWorkers.kt

@@ -21,13 +21,14 @@ object ConversationMessageComputeWorkers {
 
   fun recomputeFormattedDate(
     context: Context,
-    items: List<ConversationMessageElement>
+    items: List<ConversationMessageElement>,
+    forceUpdate: Boolean = false
   ): Single<Boolean> {
     return Single.fromCallable {
       var hasUpdatedProperties = false
       for (item in items) {
         val oldDate = item.conversationMessage.computedProperties.formattedDate
-        if (oldDate.isRelative) {
+        if (oldDate.isRelative || forceUpdate) {
           val newDate = ConversationMessage.getFormattedDate(context, item.conversationMessage.messageRecord)
           item.conversationMessage.computedProperties.formattedDate = newDate
           hasUpdatedProperties = true

app/src/main/java/org/thoughtcrime/securesms/util/JavaTimeExtensions.kt

@@ -1,7 +1,6 @@
 package org.thoughtcrime.securesms.util
 
 import android.content.Context
-import android.os.Build
 import android.text.format.DateFormat
 import java.time.DayOfWeek
 import java.time.Instant
@@ -13,7 +12,6 @@ import java.time.ZoneId
 import java.time.ZoneOffset
 import java.time.ZonedDateTime
 import java.time.format.DateTimeFormatter
-import java.time.format.FormatStyle
 import java.time.temporal.WeekFields
 import java.util.Locale
 import java.util.concurrent.TimeUnit
@@ -91,14 +89,13 @@ fun Long.toLocalTime(zoneId: ZoneId = ZoneId.systemDefault()): LocalTime {
 }
 
 /**
- * Formats [LocalTime] as localized time. For example, "8:00 AM"
+ * Formats [LocalTime] as localized time. For example, "1:45 PM" or "13:45"
  */
 fun LocalTime.formatHours(context: Context): String {
-  return if (Build.VERSION.SDK_INT >= 26 || !DateFormat.is24HourFormat(context)) {
-    DateTimeFormatter.ofLocalizedTime(FormatStyle.SHORT).format(this)
-  } else {
-    DateTimeFormatter.ofPattern("HH:mm", Locale.getDefault()).format(this)
-  }
+  // We have to create our own pattern here, since the formatter instance returned by DateTimeFormatter.ofLocalizedTime() is looked up lazily, is immutable,
+  // and is not updated when the system's 24-hour time setting changes.
+  val pattern = if (DateFormat.is24HourFormat(context)) "HH:mm" else "h:mm a"
+  return DateTimeFormatter.ofPattern(pattern, Locale.getDefault()).format(this)
 }
 
 /**