dart - 定位小部件导致 child 消失/异常

Question

我目前正在学习 Flutter，我正在尝试使用 Stacked 中的 Positioned 小部件在屏幕底部放置一个旋转木马。目前，堆栈是一张 map ，轮播位于其顶部。当我使用定位小部件将轮播移动到底部时，它消失了，我遇到了这个错误。

I/flutter (19228): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 1578 pos 12: '!_debugDoingThisLayout': is not true.
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#51ed3 relayoutBoundary=up4 NEEDS-LAYOUT NEEDS-PAINT
    Restarted application in 1,970ms.
    I/flutter (19228): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
    I/flutter (19228): The following assertion was thrown during performResize():
    I/flutter (19228): Horizontal viewport was given unbounded width.
    I/flutter (19228): Viewports expand in the scrolling direction to fill their container.In this case, a horizontal
    I/flutter (19228): viewport was given an unlimited amount of horizontal space in which to expand. This situation
    I/flutter (19228): typically happens when a scrollable widget is nested inside another scrollable widget.
    I/flutter (19228): If this widget is always nested in a scrollable widget there is no need to use a viewport because
    I/flutter (19228): there will always be enough horizontal space for the children. In this case, consider using a Row
    I/flutter (19228): instead. Otherwise, consider using the "shrinkWrap" property (or a ShrinkWrappingViewport) to size
    I/flutter (19228): the width of the viewport to the sum of the widths of its children.
    I/flutter (19228): 
    I/flutter (19228): When the exception was thrown, this was the stack:
    I/flutter (19228): #0      RenderViewport.performResize.<anonymous closure> (package:flutter/src/rendering/viewport.dart:1155:15)
    I/flutter (19228): #1      RenderViewport.performResize (package:flutter/src/rendering/viewport.dart:1182:6)
    I/flutter (19228): #2      RenderObject.layout (package:flutter/src/rendering/object.dart:1619:9)
    I/flutter (19228): #3      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #4      RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #5      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #6      RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #7      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #8      RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #9      _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #10     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #11     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #12     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #13     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #14     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #15     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #16     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #17     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #18     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #19     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #20     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #21     RenderConstrainedBox.performLayout (package:flutter/src/rendering/proxy_box.dart:258:13)
    I/flutter (19228): #22     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #23     RenderStack.performLayout (package:flutter/src/rendering/stack.dart:549:15)
    I/flutter (19228): #24     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #25     MultiChildLayoutDelegate.layoutChild (package:flutter/src/rendering/custom_layout.dart:142:11)
    I/flutter (19228): #26     _ScaffoldLayout.performLayout (package:flutter/src/material/scaffold.dart:339:7)
    I/flutter (19228): #27     MultiChildLayoutDelegate._callPerformLayout (package:flutter/src/rendering/custom_layout.dart:212:7)
    I/flutter (19228): #28     RenderCustomMultiChildLayoutBox.performLayout (package:flutter/src/rendering/custom_layout.dart:356:14)
    I/flutter (19228): #29     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #30     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #31     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #32     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #33     _RenderCustomClip.performLayout (package:flutter/src/rendering/proxy_box.dart:1188:11)
    I/flutter (19228): #34     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #35     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #36     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #37     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #38     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #39     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #40     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #41     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #42     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #43     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #44     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #45     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #46     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #47     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #48     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #49     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #50     RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:2881:13)
    I/flutter (19228): #51     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #52     RenderStack.performLayout (package:flutter/src/rendering/stack.dart:510:15)
    I/flutter (19228): #53     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #54     __RenderTheatre&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #55     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #56     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #57     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #58     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #59     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #60     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #61     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #62     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #63     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #64     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #65     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #66     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #67     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #68     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #69     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #70     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #71     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #72     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #73     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #74     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #75     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #76     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #77     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #78     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #79     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #80     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #81     RenderOffstage.performLayout (package:flutter/src/rendering/proxy_box.dart:2881:13)
    I/flutter (19228): #82     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #83     RenderStack.performLayout (package:flutter/src/rendering/stack.dart:510:15)
    I/flutter (19228): #84     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #85     __RenderTheatre&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #86     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #87     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #88     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #89     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #90     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #91     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #92     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #93     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #94     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #95     _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.performLayout (package:flutter/src/rendering/proxy_box.dart:104:13)
    I/flutter (19228): #96     RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
    I/flutter (19228): #97     RenderView.performLayout (package:flutter/src/rendering/view.dart:147:13)
    I/flutter (19228): #98     RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:1509:7)
    I/flutter (19228): #99     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:768:18)
    I/flutter (19228): #100    _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:281:19)
    I/flutter (19228): #101    _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:677:13)
    I/flutter (19228): #102    _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:219:5)
    I/flutter (19228): #103    _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
    I/flutter (19228): #104    _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
    I/flutter (19228): #105    _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:751:7)
    I/flutter (19228): #107    _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382:19)
    I/flutter (19228): #108    _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416:5)
    I/flutter (19228): #109    _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:171:12)
    I/flutter (19228): (elided one frame from package dart:async)
    I/flutter (19228): 
    I/flutter (19228): The following RenderObject was being processed when the exception was fired:
    I/flutter (19228):   RenderViewport#90797 NEEDS-LAYOUT NEEDS-PAINT
    I/flutter (19228):   creator: Viewport ← _ScrollableScope ← IgnorePointer-[GlobalKey#3c2b1] ← Semantics ← Listener ←
    I/flutter (19228):   _GestureSemantics ← RawGestureDetector-[LabeledGlobalKey<RawGestureDetectorState>#cd194] ←
    I/flutter (19228):   _ScrollSemantics-[GlobalKey#45621] ← RepaintBoundary ← CustomPaint ← RepaintBoundary ←
    I/flutter (19228):   NotificationListener<ScrollNotification> ← ⋯
    I/flutter (19228):   parentData: <none> (can use size)
    I/flutter (19228):   constraints: BoxConstraints(0.0<=w<=Infinity, h=180.0)
    I/flutter (19228):   size: MISSING
    I/flutter (19228):   axisDirection: right
    I/flutter (19228):   crossAxisDirection: down
    I/flutter (19228):   offset: _PagePosition#6c97d(offset: null, range: null..null, viewport: null, ScrollableState,
    I/flutter (19228):   PageScrollPhysics -> ClampingScrollPhysics, IdleScrollActivity#73c09, ScrollDirection.idle)
    I/flutter (19228):   anchor: 0.0
    I/flutter (19228): This RenderObject had the following child:
    I/flutter (19228):   RenderSliverFillViewport#ce224 NEEDS-LAYOUT NEEDS-PAINT
    I/flutter (19228): ════════════════════════════════════════════════════════════════════════════════════════════════════
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderViewport#90797 NEEDS-LAYOUT NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderViewport#90797 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderIgnorePointer#598aa relayoutBoundary=up11 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#4c977 relayoutBoundary=up10 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderPointerListener#2c082 relayoutBoundary=up9 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#e6e8c relayoutBoundary=up8 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: _RenderScrollSemantics#92ccd relayoutBoundary=up7 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#443e3 relayoutBoundary=up6 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#4e459 relayoutBoundary=up5 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#954aa relayoutBoundary=up4 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderConstrainedBox#b5d9f relayoutBoundary=up2 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#954aa relayoutBoundary=up4 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderConstrainedBox#b5d9f relayoutBoundary=up2
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#954aa relayoutBoundary=up4 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 1578 pos 12: '!_debugDoingThisLayout': is not true.
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#954aa relayoutBoundary=up4 NEEDS-PAINT
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3
    I/chatty  (19228): uid=10100(com.example.mapview) Thread-2 identical 13 lines
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3
    I/flutter (19228): Another exception was thrown: 'package:flutter/src/rendering/object.dart': Failed assertion: line 1578 pos 12: '!_debugDoingThisLayout': is not true.
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderDecoratedBox#1354c relayoutBoundary=up3
    I/flutter (19228): Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#954aa relayoutBoundary=up4 NEEDS-PAINT

这是我的堆栈的代码

return new MaterialApp(
      home: Scaffold(
        appBar: new AppBar(title: new Text("Commonwealth Walkway Offline Map")),
        body: Stack(
          children: <Widget>[
            FlutterMap(
              mapController: mapController,
              options: new MapOptions(
                center: new LatLng(51.1747, -115.56934),
                minZoom: 13.0,
                maxZoom: 16.0,
                zoom: 14.0,
                swPanBoundary: LatLng(51.16968, -115.58628),
                nePanBoundary: LatLng(51.1883, -115.5516),
              ),
              layers: [
                new TileLayerOptions(
                  offlineMode: true,
                  maxZoom: 16,
                  urlTemplate: "assets/map/banff/{z}/{x}/{y}.png",
                ),
                new MarkerLayerOptions(
                    markers: generateMarkers(
                        markers,
                        swiperController.move,
                        _currentIndex,
                        LatLng(51.17360, -115.57140),
                        _direction)), //_currentLocation
              ],
            ),
            Positioned(
              bottom: 1.0,
              child: Container(
                color: Colors.blue,
                height: 150.0,
                child: Swiper(
                  itemBuilder: (BuildContext context, index) {
                    return Carousels(markers[index], _update);
                  },
                  itemCount: markers.length,
                  viewportFraction: 0.8,
                  scale: 0.9,
                  loop: false,
                  controller: swiperController,
                  onIndexChanged: (index) {
                    setState(() {
                      _currentIndex = index;
                    });
                  },
                ),
              ),
            )
          ],
        ),
      ),
    );

Swiper/Carousel 包可以在这里找到: https://pub.dartlang.org/packages/flutter_swiper#-readme-tab-

Answer 1

正如您的日志所解释的那样:

“约束:BoxConstraints(0.0<=w<=Infinity, h=180.0)”

您必须定义 Container 的宽度这是您 Swiper 的父级.您还必须组织堆栈中未使用行和列定位的项目，以使其在不同屏幕上的布局保持一致。

将此行添加到您的 Container 中:

 width: MediaQuery.of(context).size.width,

这将使您的 Swiper填满屏幕 width ，您可以将其修改为任何其他值以适合您的设计。