控制台报错如下：
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (26961): The following NoSuchMethodError was thrown building ListeningBuilder(animation: Instance of
I/flutter (26961): 'DetailsInfoProvide', dirty, dependencies: [_InheritedProviders], state: _AnimatedState#34350):
I/flutter (26961): The getter 'data' was called on null.
I/flutter (26961): Receiver: null
I/flutter (26961): Tried calling: data
I/flutter (26961):
I/flutter (26961): When the exception was thrown, this was the stack:
I/flutter (26961): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
I/flutter (26961): #1 DetailsTopArea.build.<anonymous closure> (package:flutter_shop/pages/details_page/details_top_area.dart:17:66)
I/flutter (26961): #2 Provide.build.<anonymous closure> (package:provide/provide.dart:289:43)
I/flutter (26961): #3 ListeningBuilder.build (package:provide/provide.dart:629:12)
I/flutter (26961): #4 _AnimatedState.build (package:flutter/src/widgets/transitions.dart:148:48)
I/flutter (26961): #5 StatefulElement.build (package:flutter/src/widgets/framework.dart:3824:27)
I/flutter (26961): #6 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3735:15)
I/flutter (26961): #7 Element.rebuild (package:flutter/src/widgets/framework.dart:3558:5)
I/flutter (26961): #8 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3715:5)
I/flutter (26961): #9 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3863:11)
I/flutter (26961): #10 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3710:5)
I/flutter (26961): #11 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #12 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #13 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3746:16)
I/flutter (26961): #14 Element.rebuild (package:flutter/src/widgets/framework.dart:3558:5)
I/flutter (26961): #15 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3715:5)
I/flutter (26961): #16 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3710:5)
I/flutter (26961): #17 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #18 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #19 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3746:16)
I/flutter (26961): #20 Element.rebuild (package:flutter/src/widgets/framework.dart:3558:5)
I/flutter (26961): #21 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3715:5)
I/flutter (26961): #22 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3710:5)
I/flutter (26961): #23 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #24 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #25 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4875:14)
I/flutter (26961): #26 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #27 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #28 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4875:14)
I/flutter (26961): #29 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #30 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #31 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3746:16)
I/flutter (26961): #32 Element.rebuild (package:flutter/src/widgets/framework.dart:3558:5)
I/flutter (26961): #33 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3715:5)
I/flutter (26961): #34 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3710:5)
I/flutter (26961): #35 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #36 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #37 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3746:16)
I/flutter (26961): #38 Element.rebuild (package:flutter/src/widgets/framework.dart:3558:5)
I/flutter (26961): #39 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3715:5)
I/flutter (26961): #40 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3710:5)
I/flutter (26961): #41 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:4062:11)
I/flutter (26961): #42 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #43 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #44 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3746:16)
I/flutter (26961): #45 Element.rebuild (package:flutter/src/widgets/framework.dart:3558:5)
I/flutter (26961): #46 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3715:5)
I/flutter (26961): #47 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3863:11)
I/flutter (26961): #48 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3710:5)
I/flutter (26961): #49 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2954:14)
I/flutter (26961): #50 Element.updateChild (package:flutter/src/widgets/framework.dart:2757:12)
I/flutter (26961): #51 SliverMultiBoxAdaptorElement.updateChild (package:flutter/src/widgets/sliver.dart:1030:36)
I/flutter (26961): #52 SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:1015:20)
I/flutter (26961): #53 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2251:19)
I/flutter (26961): #54 SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:1008:11)
I/flutter (26961): #55 RenderSliverMultiBoxAdaptor._createOrObtainChild.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:275:23)
I/flutter (26961): #56 RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:1740:58)
I/flutter (26961): #57 PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:797:15)
I/flutter (26961): #58 RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:1740:13)
I/flutter (26961): #59 RenderSliverMultiBoxAdaptor._createOrObtainChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:264:5)
I/flutter (26961): #60 RenderSliverMultiBoxAdaptor.addInitialChild (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:348:5)
I/flutter (26961): #61 RenderSliverList.performLayout (package:flutter/src/rendering/sliver_list.dart:78:12)
I/flutter (26961): #62 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #63 RenderSliverPadding.performLayout (package:flutter/src/rendering/sliver_padding.dart:182:11)
I/flutter (26961): #64 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #65 RenderViewportBase.layoutChildSequence (package:flutter/src/rendering/viewport.dart:407:13)
I/flutter (26961): #66 RenderViewport._attemptLayout (package:flutter/src/rendering/viewport.dart:1322:12)
I/flutter (26961): #67 RenderViewport.performLayout (package:flutter/src/rendering/viewport.dart:1240:20)
I/flutter (26961): #68 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #69 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #70 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #71 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #72 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #73 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #74 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #75 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #76 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #77 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #78 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #79 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #80 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #81 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #82 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #83 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #84 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #85 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:105:13)
I/flutter (26961): #86 RenderObject.layout (package:flutter/src/rendering/object.dart:1644:7)
I/flutter (26961): #87 MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:142:11)
I/flutter (26961): #88 _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:431:7)
I/flutter (26961): #89 MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:212:7)
I/flutter (26961): #90 RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:356:14)
I/flutter (26961): #91 RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1519:7)
I/flutter (26961): #92 PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:766:18)
I/flutter (26961): #93 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:336:19)
I/flutter (26961): #94 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:701:13)
I/flutter (26961): #95 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:275:5)
I/flutter (26961): #96 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1012:15)
I/flutter (26961): #97 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:952:9)
I/flutter (26961): #98 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:864:5)
I/flutter (26961): #102 _invoke (dart:ui/hooks.dart:219:10)
I/flutter (26961): #103 _drawFrame (dart:ui/hooks.dart:178:3)
I/flutter (26961): (elided 3 frames from package dart:async)
我这里的原因是由于DetailsInfoProvide这个provide中的请求不是异步，造成了初始时data数据为空，从而导致了控制台异常抛出，而ui界面会先出现瞬间的崩溃然后变为正常。
没有使用异步处理之前的代码：
//发送请求
getGoodsInfo(String id) {
var formData = {
'goodId': id,
};
request('getGoodDetailById', formData: formData).then((val) {
var responseData = json.decode(val.toString());
goodsInfo = DetailsModel.fromJson(responseData);
notifyListeners();
});
}
使用异步处理之后的代码为(async--await)：
//发送请求 使用async--await
getGoodsInfo(String id) async {
var formData = {
'goodId': id,
};
await request('getGoodDetailById', formData: formData).then((val) {
var responseData = json.decode(val.toString());
goodsInfo = DetailsModel.fromJson(responseData);
notifyListeners();
});
}
