Implement undo last round.

app/src/main/java/me/zobrist/tichucounter/MainActivity.kt

@@ -148,7 +148,10 @@ class MainActivity : AppCompatActivity() {
                 builder.setMessage(getString(R.string.confirmClear)).setTitle(R.string.clear)
                     .setCancelable(false).setPositiveButton(getString(R.string.yes)) { dialog, _ ->
                         dialog.dismiss()
-                        clearAll()
+                        GlobalScope.launch(Dispatchers.IO) {
+                            gameRepository.newGame()
+                            historyListViewModel.updateAll()
+                        }
                     }.setNegativeButton(getString(R.string.no)) { dialog, _ ->
                         dialog.cancel()
                     }
@@ -157,7 +160,14 @@ class MainActivity : AppCompatActivity() {
                 true
             }
             R.id.action_undo -> {
-                //historyListViewModel.revertLastRound()
+                GlobalScope.launch(Dispatchers.IO) {
+                    val history = gameRepository.getActiveRoundHistory()
+                    if(history.isNotEmpty())
+                    {
+                        gameRepository.removeRoundFromHistory(history.last())
+                        historyListViewModel.updateAll()
+                    }
+                }
                 true
             }
             R.id.action_theme -> {
@@ -177,14 +187,6 @@ class MainActivity : AppCompatActivity() {
         }
     }
 
-    private fun clearAll() {
-        GlobalScope.launch(Dispatchers.IO) {
-            gameRepository.newGame()
-            historyListViewModel.updateAll()
-        }
-    }
-
-
     private fun chooseThemeDialog() {
 
         val builder = AlertDialog.Builder(this)

app/src/main/java/me/zobrist/tichucounter/fragments/HistoryListViewModel.kt

@@ -81,10 +81,12 @@ class HistoryListViewModel @Inject constructor(val gameRepository: GameRepositor
     fun updateAll() {
         viewModelScope.launch {
             val scores = gameRepository.getActiveRoundHistory()
+            if (scores != null) {
                 getHistoryA(scores)
                 getHistoryB(scores)
                 getScoreA(scores)
                 getScoreB(scores)
+            }
             scrollDown()
         }
 

app/src/main/java/me/zobrist/tichucounter/repository/GameRepository.kt

@@ -46,7 +46,20 @@ class GameRepository @Inject constructor(private  val gameDao: GameDao, private
     {
         return withContext(Dispatchers.IO) {
             val active = getActiveGame()
-            return@withContext roundDao.getAllForGame(active?.uid)
+            if(active?.uid != null)
+            {
+                return@withContext roundDao.getAllForGame(active.uid)
+            }
+            else {
+                return@withContext listOf<Round>()
+            }
+        }
+    }
+
+    suspend fun removeRoundFromHistory(round: Round)
+    {
+        withContext(Dispatchers.IO) {
+            roundDao.delete(round)
         }
     }