From d8ef37a3f6bcb38e21af7b307ab2133b294cdff4 Mon Sep 17 00:00:00 2001
From: fzyzcjy <5236035+fzyzcjy@users.noreply.github.com>
Date: Mon, 6 Jun 2022 17:34:58 +0800
Subject: [PATCH] Update slider.dart

---
 charts_flutter/example/lib/behaviors/slider.dart | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/charts_flutter/example/lib/behaviors/slider.dart b/charts_flutter/example/lib/behaviors/slider.dart
index 6b7541011..79b1cc106 100644
--- a/charts_flutter/example/lib/behaviors/slider.dart
+++ b/charts_flutter/example/lib/behaviors/slider.dart
@@ -119,7 +119,7 @@ class _SliderCallbackState extends State<SliderLine> {
       });
     }
 
-    SchedulerBinding.instance.addPostFrameCallback(rebuild);
+    _ambiguate(SchedulerBinding.instance)!.addPostFrameCallback(rebuild);
   }
 
   @override
@@ -194,3 +194,11 @@ class LinearSales {
 
   LinearSales(this.year, this.sales);
 }
+
+/// This allows a value of type T or T?
+/// to be treated as a value of type T?.
+///
+/// We use this so that APIs that have become
+/// non-nullable can still be used with `!` and `?`
+/// to support older versions of the API as well.
+T? _ambiguate<T>(T? value) => value;