fix bug:indicator too fast disappear when loadmore complete (temporary)

Author: peng8350

example/lib/ui/example/customindicator/footer_underscroll.dart

@@ -8,6 +8,7 @@
 
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
+import 'package:flutter_gifimage/flutter_gifimage.dart';
 import 'package:pull_to_refresh/pull_to_refresh.dart';
 
 import '../../Item.dart';

lib/src/internals/indicator_wrap.dart

@@ -384,6 +384,9 @@ abstract class LoadIndicatorState<T extends LoadIndicator> extends State<T>
         return;
       }
 
+      // this line for patch bug temporary:indicator disappears fastly when load more complete
+      if(mounted)
+        Scrollable.of(context).position.correctBy(0.00001);
       WidgetsBinding.instance.addPostFrameCallback((_) {
         if (mounted && _position?.outOfRange == true) {
           activity.delegate.goBallistic(0);

lib/src/smart_refresher.dart

@@ -737,17 +737,18 @@ class RefreshController {
   }
 
   /// end twoLeveling,will return back first floor
-  void twoLevelComplete(
+  Future<void> twoLevelComplete(
       {Duration duration: const Duration(milliseconds: 500),
       Curve curve: Curves.linear}) {
     headerMode?.value = RefreshStatus.twoLevelClosing;
     WidgetsBinding.instance.addPostFrameCallback((_) {
-      position
+      return position
           .animateTo(0.0, duration: duration, curve: curve)
           .whenComplete(() {
         headerMode.value = RefreshStatus.idle;
       });
     });
+    return null;
   }
 
   /// request failed,the header display failed state