diff --git a/android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/MainActivity.kt b/android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/MainActivity.kt
index f62262a..f9646eb 100644
--- a/android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/MainActivity.kt
+++ b/android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/MainActivity.kt
@@ -1678,6 +1678,7 @@ class MainActivity : Activity() {
     }
 
     private fun refreshCurrentUi() {
+        if (!::lessonTitleText.isInitialized) return
         val item = controller.currentTrainingItem()
         lessonTitleText.text = item?.title ?: "未选择课程"
         currentSentenceCount = item?.sentences?.size ?: 0