Question

我正在尝试创建 Stepper，这是我的代码，我从 flutter doc 复制粘贴：

class AdFormView extends GetView<AdFormController> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Stepper'),
        centerTitle: true,
      ),
      body: Center(
        child: MyStatefulWidget(),
      ),
    );
  }
}

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

  @override
  _MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}

/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  int _index = 0;
  Widget build(BuildContext context) {
    return Container(
      height: 300,
      width: 300,
      child: Stepper(
        currentStep: _index,
        onStepCancel: () {
          if (_index <= 0) {
            return;
          }
          setState(() {
            _index--;
          });
        },
        onStepContinue: () {
          if (_index >= 1) {
            return;
          }
          setState(() {
            _index++;
          });
        },
        onStepTapped: (index) {
          setState(() {
            _index = index;
          });
        },
        steps: [
          Step(
            title: Text("Step 1 title"),
            content: Container(
                height: 400,
                width: 400,
                alignment: Alignment.centerLeft,
                child: Text("Content for Step 1")),
          ),
          Step(
            title: Text("Step 2 title"),
            content: Container(
              height: 400,
              width: 400,
              child: Text("Content for Step 2"),
            ),
          ),
        ],
      ),
    );
  }
}

但是我遇到了这个错误：

The following assertion was thrown during performLayout():
BoxConstraints forces an infinite width.
Stepper

The following RenderObject was being processed when the exception was fired: RenderConstrainedBox#79f3a relayoutBoundary=up19 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
RenderObject: RenderConstrainedBox#79f3a relayoutBoundary=up19 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
    parentData: offset=Offset(0.0, 0.0) (can use size)
    constraints: BoxConstraints(0.0<=w<=Infinity, 0.0<=h<=48.0)
    size: MISSING
    additionalConstraints: BoxConstraints(w=Infinity, 0.0<=h<=Infinity)
    child: RenderPhysicalShape#0b08e NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
        needs compositing
        parentData: <none>
        constraints: MISSING
        size: MISSING
        elevation: 0.0
        color: Color(0xff002c7f)
        shadowColor: Color(0xff002c7f)
        clipper: ShapeBorderClipper
        child: RenderCustomPaint#df4fd NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
            parentData: <none>
            constraints: MISSING
            size: MISSING
            child: _RenderInkFeatures#570e6 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
                parentData: <none>
                constraints: MISSING
                size: MISSING
                child: RenderSemanticsAnnotations#f05ee NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
                    parentData: <none>
                    constraints: MISSING
                    size: MISSING

父级有大小，为什么它显示 MISSING？我尝试添加最大和最小宽度和高度，并尝试将其包裹在灵活中，但没有任何效果！

我创建了一个新项目来测试 Stepper，我创建了一个正常的颤振和一个使用 GetX 它们运行良好。

我不知道为什么它在我的项目中不起作用，我将代码复制粘贴，我不知道为什么它无法读取父级的大小，我添加了最大宽度，最小宽度，最大高度, 最小高度、宽度和高度并且不起作用。

所以它不仅仅适用于我的项目，如下图所示：

Answer 1

MyStatefulWidget 上没有此类错误，您可以使用 flutter clean 重建项目，然后运行。这个问题可能是由父级引起的。

Flutter Stepper - BoxConstraints 强制无限宽度

1 个答案: