增加下拉刷新效果

Author: CarGuo

lib/page/dynamic_page.dart

@@ -35,8 +35,8 @@ class _DynamicPageState extends State<DynamicPage>
   showRefreshLoading() {
     ///直接触发下拉
     new Future.delayed(const Duration(milliseconds: 500), () {
-      scrollController.animateTo(-100,
-          duration: Duration(milliseconds: 500), curve: Curves.linear);
+      scrollController.animateTo(-141,
+          duration: Duration(milliseconds: 600), curve: Curves.linear);
       return true;
     });
   }

lib/widget/gsy_pull_new_load_widget.dart

@@ -1,8 +1,13 @@
+import 'package:flare_flutter/flare_actor.dart';
 import 'package:flutter/cupertino.dart' as IOS;
 import 'package:flutter/material.dart';
 import 'package:flutter_spinkit/flutter_spinkit.dart';
 import 'package:gsy_github_app_flutter/common/style/gsy_style.dart';
 import 'package:gsy_github_app_flutter/common/utils/common_utils.dart';
+import 'dart:math';
+
+const double iosRefreshHeight = 140;
+const double iosRefreshIndicatorExtent = 100;
 
 ///通用下上刷新控件
 class GSYPullLoadWidget extends StatefulWidget {
@@ -172,14 +177,18 @@ class _GSYPullLoadWidgetState extends State<GSYPullLoadWidget> {
       ///用ios模式的下拉刷新
       return CustomScrollView(
         controller: _scrollController,
+
         ///回弹效果
-        physics: const BouncingScrollPhysics(
+        physics: const CustomBouncingScrollPhysics(
           parent: AlwaysScrollableScrollPhysics(),
         ),
         slivers: <Widget>[
           ///控制显示刷新的 CupertinoSliverRefreshControl
           IOS.CupertinoSliverRefreshControl(
+            refreshIndicatorExtent: iosRefreshIndicatorExtent,
+            refreshTriggerPullDistance: iosRefreshHeight,
             onRefresh: handleRefresh,
+            builder: buildSimpleRefreshIndicator,
           ),
           SliverSafeArea(
             sliver: SliverList(
@@ -276,6 +285,28 @@ class _GSYPullLoadWidgetState extends State<GSYPullLoadWidget> {
       ),
     );
   }
+
+  Widget buildSimpleRefreshIndicator(
+    BuildContext context,
+    IOS.RefreshIndicatorMode refreshState,
+    double pulledExtent,
+    double refreshTriggerPullDistance,
+    double refreshIndicatorExtent,
+  ) {
+    return Align(
+      alignment: Alignment.bottomCenter,
+      child: new Container(
+          color: Colors.black,
+          width: MediaQuery.of(context).size.width,
+          ///动态大小处理
+          height: pulledExtent > iosRefreshHeight ? pulledExtent : iosRefreshHeight,
+          child: FlareActor("static/file/loading_world_now.flr",
+              alignment: Alignment.topCenter,
+              fit: BoxFit.cover,
+              animation: "Earth Moving"),
+        ),
+    );
+  }
 }
 
 class GSYPullLoadWidgetControl extends ChangeNotifier {
@@ -322,3 +353,96 @@ class GSYPullLoadWidgetControl extends ChangeNotifier {
   ///是否加载中
   bool isLoading = false;
 }
+
+///自定义弹性滑动模块
+class CustomBouncingScrollPhysics extends ScrollPhysics {
+  const CustomBouncingScrollPhysics({ScrollPhysics parent})
+      : super(parent: parent);
+
+  @override
+  CustomBouncingScrollPhysics applyTo(ScrollPhysics ancestor) {
+    return CustomBouncingScrollPhysics(parent: buildParent(ancestor));
+  }
+
+  double frictionFactor(double overscrollFraction) =>
+      0.52 * pow(1 - overscrollFraction, 2);
+
+  @override
+  double applyPhysicsToUserOffset(ScrollMetrics position, double offset) {
+    assert(offset != 0.0);
+    assert(position.minScrollExtent <= position.maxScrollExtent);
+    if (!position.outOfRange) return offset;
+
+    /// -2 是因为有时候会只到 iosRefreshHeight - 1
+    /// 会导致触发重新又从0开始的问题
+    if (position.pixels.abs() >= (iosRefreshHeight - 2)) {
+      return 0;
+    }
+    final double overscrollPastStart =
+        max(position.minScrollExtent - position.pixels, 0.0);
+    final double overscrollPastEnd =
+        max(position.pixels - position.maxScrollExtent, 0.0);
+    final double overscrollPast = max(overscrollPastStart, overscrollPastEnd);
+
+    final bool easing = (overscrollPastStart > 0.0 && offset < 0.0) ||
+        (overscrollPastEnd > 0.0 && offset > 0.0);
+
+    final double friction = easing
+        ? frictionFactor(
+            (overscrollPast - offset.abs()) / position.viewportDimension)
+        : frictionFactor(overscrollPast / position.viewportDimension);
+
+
+
+    final double direction = offset.sign;
+
+    print("easing $easing overscrollPastStart $overscrollPastStart");
+
+    return direction * _applyFriction(overscrollPast, offset.abs(), friction);
+  }
+
+  static double _applyFriction(
+      double extentOutside, double absDelta, double gamma) {
+    assert(absDelta > 0);
+    double total = 0.0;
+    if (extentOutside > 0) {
+      final double deltaToLimit = extentOutside / gamma;
+      if (absDelta < deltaToLimit) return absDelta * gamma;
+      total += extentOutside;
+      absDelta -= deltaToLimit;
+    }
+    return total + absDelta;
+  }
+
+  @override
+  double applyBoundaryConditions(ScrollMetrics position, double value) => 0.0;
+
+  @override
+  Simulation createBallisticSimulation(
+      ScrollMetrics position, double velocity) {
+    final Tolerance tolerance = this.tolerance;
+    if (velocity.abs() >= tolerance.velocity || position.outOfRange) {
+      return BouncingScrollSimulation(
+        spring: spring,
+        position: position.pixels,
+        velocity: velocity * 0.91,
+        leadingExtent: position.minScrollExtent,
+        trailingExtent: position.maxScrollExtent,
+        tolerance: tolerance,
+      );
+    }
+    return null;
+  }
+
+  @override
+  double get minFlingVelocity => 50.0 * 2.0;
+
+  @override
+  double carriedMomentum(double existingVelocity) {
+    return existingVelocity.sign *
+        min(0.000816 * pow(existingVelocity.abs(), 1.967).toDouble(), 40000.0);
+  }
+
+  @override
+  double get dragStartDistanceMotionThreshold => 3.5;
+}

pubspec.yaml

@@ -102,6 +102,7 @@ flutter:
     - static/file/rejection.json
     - static/file/rejection2.json
     - static/file/flare_flutter_2.flr
+    - static/file/loading_world_now.flr
 
   fonts:
     - family: wxcIconFont