exception - Flutter:有 2 个 FloatingActionButton 时出现异常

Question

当此构建涉及 2 个 FloatingActionButton 时，我第一次构建页面时收到异常。

但是，如果我注释掉 2 个 FloatingActionButton 之一，运行该应用程序并在稍后阶段取消注释并继续进行热重载，它会起作用。

以下代码实现了一个图像选择器，并让用户可以选择从图库或相机中进行选择。

有人可以看看这个并告诉我我做错了什么吗？

我已经突出显示了导致异常的代码部分。

代码如下:

class ProfilePage extends StatefulWidget {
  ProfilePage(this.profileId);
  final int profileId;
  @override
  _ProfilePageState createState() => new _ProfilePageState();
}

class _ProfilePageState extends State<ProfilePage> {
  var _imageInfo;

  @override
  void initState() {
    _imageInfo = mid.currentProfile['Photo'];
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(Translations
            .of(context)
            .text(widget.profileId == -1 ? 'profiles_add' : 'profiles_edit')),
        actions: <Widget>[
          new IconButton(
            icon: new Icon(Icons.close),
            onPressed: () => Navigator.of(context).pop(null),
          ),
        ],
        leading: new Container(),
      ),
      body: _build_body(),
    );
  }

  _build_body() {
    var profileImage;
    profileImage = new Center(
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          new GestureDetector(
            child: new Container(
              child: new ProfilePicture(imageInfo: _imageInfo),
              width: 100.0,
              height: 100.0,
              alignment: Alignment.center,
            ),
            onTap: () {},
          ),
  // ##################################  
          new FloatingActionButton(
            onPressed: () {
              getImage(ImageSource.camera);
            },
            tooltip: 'Take a Photo',
            child: new Icon(Icons.camera_alt)
          ),
          new FloatingActionButton(
              onPressed: () {
                getImage(ImageSource.gallery);
              },
              tooltip: 'Pick Image from gallery',
              child: new Icon(Icons.photo_library)
          ),
  // ##################################
        ],
      ),
    );

    return new Container(
      child: new Column(
        children: [profileImage],
        crossAxisAlignment: CrossAxisAlignment.start,
        mainAxisSize: MainAxisSize.min,
      ),
    );
  }

  Future<dynamic> getImage(ImageSource source) async {
    var imageFile = await ImagePicker.pickImage(source: source);

    if (imageFile != null) {
      List<int> imageBytes = imageFile.readAsBytesSync();
      String base64Image = base64.encode(imageBytes);

      setState(() {
        _imageInfo = "base64:" + base64Image;
      });
    }
  }
}

异常(exception)情况:

I/flutter ( 9045): ══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 9045): The following assertion was thrown during a scheduler callback:
I/flutter ( 9045): There are multiple heroes that share the same tag within a subtree.
I/flutter ( 9045): Within each subtree for which heroes are to be animated (typically a PageRoute subtree), each Hero
I/flutter ( 9045): must have a unique non-null tag.
I/flutter ( 9045): In this case, multiple heroes had the following tag: <default FloatingActionButton tag>
I/flutter ( 9045): Here is the subtree for one of the offending heroes:
I/flutter ( 9045): # Hero(tag: <default FloatingActionButton tag>, state: _HeroState#5ea48)
I/flutter ( 9045): # └KeyedSubtree-[GlobalKey#d064f]
I/flutter ( 9045): #  └RawMaterialButton(state: _RawMaterialButtonState#8f3c6)
I/flutter ( 9045): #   └Semantics(container: true, properties: SemanticsProperties, label: null, value: null, hint: null, renderObject: RenderSemanticsAnnotations#d7c9b relayoutBoundary=up5 NEEDS-PAINT)
I/flutter ( 9045): #    └ConstrainedBox(BoxConstraints(w=56.0, h=56.0), renderObject: RenderConstrainedBox#8437c relayoutBoundary=up6 NEEDS-PAINT)
I/flutter ( 9045): #     └Material(type: button, elevation: 6.0, color: Color(0xff2196f3), textStyle.debugLabel: ((englishLike button).merge(whiteMountainView button)).copyWith, textStyle.inherit: false, textStyle.color: Color(0xffffffff), textStyle.family: Roboto, textStyle.size: 14.0, textStyle.weight: 500, textStyle.letterSpacing: 1.2, textStyle.baseline: alphabetic, textStyle.decoration: TextDecoration.none, shape: CircleBorder(BorderSide(Color(0xff000000), 0.0, BorderStyle.none)), state: _MaterialState#73b5e)
I/flutter ( 9045): #      └_MaterialInterior(duration: 200ms, shape: CircleBorder(BorderSide(Color(0xff000000), 0.0, BorderStyle.none)), elevation: 6.0, color: Color(0xff2196f3), shadowColor: Color(0xff000000), state: _MaterialInteriorState#aa4b9(ticker inactive))
I/flutter ( 9045): #       └PhysicalShape(clipper: ShapeBorderClipper, elevation: 6.0, color: Color(0xff2196f3), shadowColor: Color(0xff000000), renderObject: RenderPhysicalShape#0486d NEEDS-PAINT)
I/flutter ( 9045): #        └_ShapeBorderPaint
I/flutter ( 9045): #         └CustomPaint(renderObject: RenderCustomPaint#7e004 NEEDS-PAINT)
I/flutter ( 9045): #          └NotificationListener<LayoutChangedNotification>
I/flutter ( 9045): #           └_InkFeatures-[GlobalKey#f1e6b ink renderer](renderObject: _RenderInkFeatures#34dbd NEEDS-PAINT)
I/flutter ( 9045): #            └AnimatedDefaultTextStyle(duration: 200ms, debugLabel: ((englishLike button).merge(whiteMountainView button)).copyWith, inherit: false, color: Color(0xffffffff), family: Roboto, size: 14.0, weight: 500, letterSpacing: 1.2, baseline: alphabetic, decoration: TextDecoration.none, softWrap: wrapping at box width, overflow: clip, state: _AnimatedDefaultTextStyleState#c8a96(ticker inactive))
I/flutter ( 9045): #             └DefaultTextStyle(debugLabel: ((englishLike button).merge(whiteMountainView button)).copyWith, inherit: false, color: Color(0xffffffff), family: Roboto, size: 14.0, weight: 500, letterSpacing: 1.2, baseline: alphabetic, decoration: TextDecoration.none, softWrap: wrapping at box width, overflow: clip)
I/flutter ( 9045): #              └InkWell(gestures: [tap], clipped to BoxShape.rectangle, state: _InkResponseState<InkResponse>#32f3c)
I/flutter ( 9045): #               └GestureDetector
I/flutter ( 9045): #                └RawGestureDetector(state: RawGestureDetectorState#d6211(gestures: [tap], behavior: opaque))
I/flutter ( 9045): #                 └_GestureSemantics(renderObject: RenderSemanticsGestureHandler#d616c NEEDS-PAINT)
I/flutter ( 9045): #                  └Listener(listeners: [down], behavior: opaque, renderObject: RenderPointerListener#8a585 NEEDS-PAINT)
I/flutter ( 9045): #                   └Builder
I/flutter ( 9045): #                    └IconTheme(IconThemeData#15fa8(color: Color(0xffffffff)))
I/flutter ( 9045): #                     └Container(padding: EdgeInsets.zero)
I/flutter ( 9045): #                      └Padding(padding: EdgeInsets.zero, renderObject: RenderPadding#45f72 NEEDS-PAINT)
I/flutter ( 9045): #                       └Center(alignment: center, widthFactor: 1.0, heightFactor: 1.0, renderObject: RenderPositionedBox#a4315 NEEDS-PAINT)
I/flutter ( 9045): #                        └SizedBox.expand(renderObject: RenderConstrainedBox#af3fc relayoutBoundary=up1 NEEDS-PAINT)
I/flutter ( 9045): #                         └Tooltip("Pick Image from gallery", vertical offset: 24.0, position: below, state: _TooltipState#36588(ticker inactive))
I/flutter ( 9045): #                          └GestureDetector
I/flutter ( 9045): #                           └RawGestureDetector(state: RawGestureDetectorState#6cd1d(gestures: [long press], behavior: opaque))
I/flutter ( 9045): #                            └Listener(listeners: [down], behavior: opaque, renderObject: RenderPointerListener#aae3f NEEDS-PAINT)
I/flutter ( 9045): #                             └Semantics(container: false, properties: SemanticsProperties, label: "Pick Image from gallery", value: null, hint: null, renderObject: RenderSemanticsAnnotations#5fa0a NEEDS-PAINT)
I/flutter ( 9045): #                              └Builder
I/flutter ( 9045): #                               └IconTheme(IconThemeData#15fa8(color: Color(0xffffffff)))
I/flutter ( 9045): #                                └Icon(IconData(U+0E413))
I/flutter ( 9045): #                                 └Semantics(container: false, properties: SemanticsProperties, label: null, value: null, hint: null, renderObject: RenderSemanticsAnnotations#8a909 NEEDS-PAINT)
I/flutter ( 9045): #                                  └ExcludeSemantics(excluding: true, renderObject: RenderExcludeSemantics#fc581 NEEDS-PAINT)
I/flutter ( 9045): #                                   └SizedBox(width: 24.0, height: 24.0, renderObject: RenderConstrainedBox#f68c4 NEEDS-PAINT)
I/flutter ( 9045): #                                    └Center(alignment: center, renderObject: RenderPositionedBox#c38ac NEEDS-PAINT)
I/flutter ( 9045): #                                     └RichText(textDirection: ltr, softWrap: wrapping at box width, maxLines: unlimited, text: "", renderObject: RenderParagraph#8873e relayoutBoundary=up1 NEEDS-PAINT)
I/flutter ( 9045):
I/flutter ( 9045): When the exception was thrown, this was the stack:
I/flutter ( 9045): #0      Hero._allHeroesFor.visitor.<anonymous closure> (package:flutter/src/widgets/heroes.dart:130:13)
I/flutter ( 9045): #1      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:140:10)
I/flutter ( 9045): #2      ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #3      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #4      SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625:14)
I/flutter ( 9045): #5      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #6      MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4725:16)
I/flutter ( 9045): #7      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #8      SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625:14)
I/flutter ( 9045): #9      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #10     MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4725:16)
I/flutter ( 9045): #11     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #12     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #13     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #14     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #15     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #16     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #17     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #18     MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4725:16)
I/flutter ( 9045): #19     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #20     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #21     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #22     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #23     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #24     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #25     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #26     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625:14)
I/flutter ( 9045): #27     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #28     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #29     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #30     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625:14)
I/flutter ( 9045): #31     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #32     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #33     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #34     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #35     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #36     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #37     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #38     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #39     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #40     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #41     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #42     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #43     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #44     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3659:14)
I/flutter ( 9045): #45     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:144:15)
I/flutter ( 9045): #46     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625:14)
I/flutter ( 9045): #47     Element.visitChildElements (package:flutter/src/widgets/framework.dart:2625:5)
I/flutter ( 9045): #48     Hero._allHeroesFor (package:flutter/src/widgets/heroes.dart:146:13)
I/flutter ( 9045): #49     HeroController._startHeroTransition (package:flutter/src/widgets/heroes.dart:511:51)
I/flutter ( 9045): #50     HeroController._maybeStartHeroTransition.<anonymous closure> (package:flutter/src/widgets/heroes.dart:492:9)
I/flutter ( 9045): #51     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter ( 9045): #52     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:938:9)
I/flutter ( 9045): #53     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter ( 9045): #54     _invoke (dart:ui/hooks.dart:120:13)
I/flutter ( 9045): #55     _drawFrame (dart:ui/hooks.dart:109:3)
I/flutter ( 9045): ════════════════════════════════════════════════════════════════════════════════════════════════════

Answer 1

好的，我发现将 heroTag: null 添加到 FloatingActionButton 的属性中可以解决问题。

导致异常的代码部分现在如下并且似乎可以正常工作:

      new FloatingActionButton(
        onPressed: () {
          getImage(ImageSource.camera);
        },
        tooltip: 'Take a Photo',
        child: new Icon(Icons.camera_alt),
        heroTag: null,
      ),

      new FloatingActionButton(
          onPressed: () {
            getImage(ImageSource.gallery);
          },
          tooltip: 'Pick Image from gallery',
          child: new Icon(Icons.photo_library),
          heroTag: null,
      ),