added android:maxLength="200" to messages_fragment.xml

app/src/main/res/layout/messages_fragment.xml

@@ -33,6 +33,7 @@
             android:id="@+id/messageInputText"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:maxLength="200"
             android:imeOptions="actionDone"
             android:text="" />