【发布时间】：2019-01-02 19:58:43
【问题描述】：
我想要一个对话框，引导我的用户完成身份验证流程。它将需要以下小部件：
- 选择身份验证方法（Google、Facebook、电子邮件、电话等）
- 输入电子邮件地址
- 输入电话号码
- 输入来自（电子邮件/电话）的代码
我要做的是创建一个带有 PageView 小部件的 AlertDialog，该小部件将通过 PageController 导航（我设置了 physics: NeverScrollableScrollPhysics() 以防止用户滚动）。这里的整个想法是我希望对话框始终保持相同的大小（我知道 PageView 将测量所有的孩子并且应该允许我这样做。
我尝试使用 3 个 Text 小部件创建 PageView，但出现以下错误：
I/flutter (16052): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (16052): The following assertion was thrown during performLayout():
I/flutter (16052): RenderViewport does not support returning intrinsic dimensions.
I/flutter (16052): Calculating the intrinsic dimensions would require instantiating every child of the viewport, which
I/flutter (16052): defeats the point of viewports being lazy.
I/flutter (16052): If you are merely trying to shrink-wrap the viewport in the main axis direction, consider a
I/flutter (16052): RenderShrinkWrappingViewport render object (ShrinkWrappingViewport widget), which achieves that
I/flutter (16052): effect without implementing the intrinsic dimension API.
I/flutter (16052):
I/flutter (16052): When the exception was thrown, this was the stack:
I/flutter (16052): #0 RenderViewportBase.debugThrowIfNotCheckingIntrinsics.<anonymous closure> (package:flutter/src/rendering/viewport.dart:299:9)
I/flutter (16052): #1 RenderViewportBase.debugThrowIfNotCheckingIntrinsics (package:flutter/src/rendering/viewport.dart:309:6)
I/flutter (16052): #2 RenderViewportBase.computeMaxIntrinsicWidth (package:flutter/src/rendering/viewport.dart:321:12)
I/flutter (16052): #3 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #4 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #5 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #6 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #7 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #8 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #9 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #10 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #11 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #12 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #13 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #14 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #15 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #16 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #17 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #18 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #19 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #20 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #21 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #22 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #23 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #24 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #25 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #26 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #27 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #28 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #29 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #30 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #31 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #32 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #33 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #34 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #35 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #36 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #37 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #38 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #39 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #40 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #41 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #42 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.computeMaxIntrinsicWidth (package:flutter/src/rendering/proxy_box.dart:76:20)
I/flutter (16052): #43 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #44 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #45 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #46 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #47 RenderPadding.computeMaxIntrinsicWidth (package:flutter/src/rendering/shifted_box.dart:163:20)
I/flutter (16052): #48 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #49 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #50 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #51 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #52 RenderFlex.computeMaxIntrinsicWidth.<anonymous closure> (package:flutter/src/rendering/flex.dart:575:60)
I/flutter (16052): #53 RenderFlex._getIntrinsicSize (package:flutter/src/rendering/flex.dart:552:58)
I/flutter (16052): #54 RenderFlex.computeMaxIntrinsicWidth (package:flutter/src/rendering/flex.dart:572:12)
I/flutter (16052): #55 RenderBox._computeIntrinsicDimension.<anonymous closure> (package:flutter/src/rendering/box.dart:1099:23)
I/flutter (16052): #56 __InternalLinkedHashMap&_HashVMBase&MapMixin&_LinkedHashMapMixin.putIfAbsent (dart:collection/runtime/libcompact_hash.dart:284:23)
I/flutter (16052): #57 RenderBox._computeIntrinsicDimension (package:flutter/src/rendering/box.dart:1097:41)
I/flutter (16052): #58 RenderBox.getMaxIntrinsicWidth (package:flutter/src/rendering/box.dart:1281:12)
I/flutter (16052): #59 RenderIntrinsicWidth.performLayout (package:flutter/src/rendering/proxy_box.dart:617:36)
I/flutter (16052): #60 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #61 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #62 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #63 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #64 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #65 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #66 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #67 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #68 _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1188:11)
I/flutter (16052): #69 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #70 RenderConstrainedBox.performLayout (package:flutter/src/rendering/proxy_box.dart:258:13)
I/flutter (16052): #71 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #72 RenderPositionedBox.performLayout (package:flutter/src/rendering/shifted_box.dart:385:13)
I/flutter (16052): #73 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #74 RenderPadding.performLayout (package:flutter/src/rendering/shifted_box.dart:199:11)
I/flutter (16052): #75 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #76 RenderPadding.performLayout (package:flutter/src/rendering/shifted_box.dart:199:11)
I/flutter (16052): #77 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #78 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #79 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #80 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #81 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #82 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #83 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #84 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #85 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #86 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #87 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #88 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #89 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #90 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
I/flutter (16052): #91 RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:2881:13)
I/flutter (16052): #92 RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (16052): #93 RenderStack.performLayout (package:flutter/src/rendering/stack.dart:510:15)
I/flutter (16052): #94 RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1509:7)
I/flutter (16052): #95 PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:768:18)
I/flutter (16052): #96 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:281:19)
I/flutter (16052): #97 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:677:13)
I/flutter (16052): #98 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:219:5)
I/flutter (16052): #99 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (16052): #100 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter (16052): #101 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter (16052): #102 _invoke (dart:ui/hooks.dart:154:13)
I/flutter (16052): #103 _drawFrame (dart:ui/hooks.dart:143:3)
I/flutter (16052):
I/flutter (16052): The following RenderObject was being processed when the exception was fired:
I/flutter (16052): RenderIntrinsicWidth#88cfa relayoutBoundary=up6 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): creator: IntrinsicWidth ← Semantics ← DefaultTextStyle ← AnimatedDefaultTextStyle ←
I/flutter (16052): _InkFeatures-[GlobalKey#8e5bb ink renderer] ← NotificationListener<LayoutChangedNotification> ←
I/flutter (16052): CustomPaint ← _ShapeBorderPaint ← PhysicalShape ← _MaterialInterior ← Material ← ConstrainedBox ←
I/flutter (16052): ⋯
I/flutter (16052): parentData: <none> (can use size)
I/flutter (16052): constraints: BoxConstraints(280.0<=w<=331.4, 0.0<=h<=611.4)
I/flutter (16052): size: MISSING
I/flutter (16052): stepWidth: null
I/flutter (16052): stepHeight: null
I/flutter (16052): This RenderObject had the following descendants (showing up to depth 5):
I/flutter (16052): RenderFlex#1cdae NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderPadding#3c952 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderRepaintBoundary#2e299 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderCustomPaint#4dd7f NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderRepaintBoundary#ebf6b NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderPadding#31e20 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderFlex#8072a NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderPadding#a5f11 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): RenderSemanticsAnnotations#f63f2 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (16052): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (16052): Another exception was thrown: RenderBox was not laid out: RenderIntrinsicWidth#88cfa relayoutBoundary=up6 NEEDS-PAINT
I/flutter (16052): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#ca67f relayoutBoundary=up5 NEEDS-PAINT
I/flutter (16052): Another exception was thrown: RenderBox was not laid out: _RenderInkFeatures#a2ca4 relayoutBoundary=up4 NEEDS-PAINT
I/flutter (16052): Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#b4d9b relayoutBoundary=up3 NEEDS-PAINT
I/flutter (16052): Another exception was thrown: RenderBox was not laid out: RenderPhysicalShape#235a2 relayoutBoundary=up2 NEEDS-PAINT
I/flutter (16052): Another exception was thrown: 'package:flutter/src/rendering/shifted_box.dart': Failed assertion: line 314 pos 12: 'child.hasSize': is not true.
I/flutter (16052): Another exception was thrown: RenderBox was not laid out: RenderPhysicalShape#235a2 relayoutBoundary=up2
如果有更好的方法可以做到这一点，只要对话框不会调整大小，我就愿意接受。
更新：
这是一个最小示例，只需启动以下对话框：
AlertDialog(
content: PageView(
children: <Widget> [
Text('child1'),
Text('child2'),
Text('child3'),
],
),
);
问题似乎是 PageView 不会立即实例化所有视图，而是延迟执行以节省 CPU 周期。这意味着 AlertDialog 无法自行调整大小。我想知道是否有办法覆盖 PageView 的默认行为并让它立即测量它的大小？
更新：
虽然我无法使用 PageView 做任何事情，但我已经能够使用简单的 IndexedStack 来模仿我想要的行为。它只是在以编程方式在页面之间移动时缺少动画，但希望我能够添加它。完成后我会发布最终答案。
【问题讨论】：
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标签： flutter