Fix #1592: Previous responses header collapsed state not retained across landscape changes

app/src/main/java/org/oppia/android/app/player/state/StateFragment.kt

@@ -170,5 +170,11 @@ class StateFragment :
       STATE_FRAGMENT_STATE_KEY,
       stateFragmentPresenter.getUserAnswerState()
     )
+    stateFragmentPresenter.saveExpandedState(outState)
+  }
+
+  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+    super.onViewCreated(view, savedInstanceState)
+    stateFragmentPresenter.restoreExpandedState(savedInstanceState)
   }
 }

app/src/main/java/org/oppia/android/app/player/state/StateFragmentPresenter.kt

@@ -1,6 +1,7 @@
 package org.oppia.android.app.player.state
 
 import android.content.Context
+import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
@@ -617,4 +618,12 @@ class StateFragmentPresenter @Inject constructor(
       SurveyQuestionName.NPS
     )
   }
+
+  fun saveExpandedState(outState: Bundle) {
+    recyclerViewAssembler.saveExpandedState(outState)
+  }
+
+  fun restoreExpandedState(savedInstanceState: Bundle?) {
+    recyclerViewAssembler.restoreExpandedState(savedInstanceState)
+  }
 }

app/src/main/java/org/oppia/android/app/player/state/StatePlayerRecyclerViewAssembler.kt

@@ -1,6 +1,7 @@
 package org.oppia.android.app.player.state
 
 import android.content.Context
+import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.animation.AccelerateInterpolator
@@ -1506,4 +1507,15 @@ class StatePlayerRecyclerViewAssembler private constructor(
       }
     }
   }
+
+  /** Saves the expanded state to a Bundle. */
+  fun saveExpandedState(outState: Bundle) {
+    outState.putBoolean("hasPreviousResponsesExpanded", hasPreviousResponsesExpanded)
+  }
+
+  /** Restores the expanded state from a Bundle. */
+  fun restoreExpandedState(savedInstanceState: Bundle?) {
+    hasPreviousResponsesExpanded =
+      savedInstanceState?.getBoolean("hasPreviousResponsesExpanded", false) ?: false
+  }
 }