1.优化下拉刷新图标支持颜色传参

lib/widgets/refresh/refresh_header/refresh_header.dart

@@ -5,8 +5,8 @@ import 'package:pull_to_refresh/pull_to_refresh.dart';
 class RefreshHeader extends StatelessWidget {
   final double offsetY;
   final double _height = 44;
-
-  const RefreshHeader({Key key, this.offsetY = 0}) : super(key: key);
+  final Color color;
+  const RefreshHeader({Key key, this.offsetY = 0,this.color=Colors.white}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
@@ -22,7 +22,7 @@ class RefreshHeader extends StatelessWidget {
               height: 36,
               child: LoadingIndicator(
                 indicatorType: Indicator.ballSpinFadeLoader,
-                color: Colors.white,
+                color: color,
               ),
             ),
           ),