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垂直ビューポートに制限のない高さが与えられました

私ははためくのは初めてです。グリッドビューを中央に配置するだけです。

enter image description here

以下は私が試したコードです：

  @override
  Widget build(BuildContext context) {
    return new Material(
      color: Colors.deepPurpleAccent,
      child: new Column(
       mainAxisAlignment: MainAxisAlignment.center,
          children:<Widget>[new GridView.count(crossAxisCount: _column,children: new List.generate(_row*_column, (index) {
            return new Center(
                child: new CellWidget()
            );
          }),)]
      )
    );
  }

次の例外：

    I/flutter ( 9925): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 9925): The following assertion was thrown during performResize():
I/flutter ( 9925): Vertical viewport was given unbounded height.
I/flutter ( 9925): Viewports expand in the scrolling direction to fill their container.In this case, a vertical
I/flutter ( 9925): viewport was given an unlimited amount of vertical space in which to expand. This situation
I/flutter ( 9925): typically happens when a scrollable widget is nested inside another scrollable widget.
I/flutter ( 9925): If this widget is always nested in a scrollable widget there is no need to use a viewport because
I/flutter ( 9925): there will always be enough vertical space for the children. In this case, consider using a Column
I/flutter ( 9925): instead. Otherwise, consider using the "shrinkWrap" property (or a ShrinkWrappingViewport) to size
I/flutter ( 9925): the height of the viewport to the sum of the heights of its children.
I/flutter ( 9925): 
I/flutter ( 9925): When the exception was thrown, this was the stack:
I/flutter ( 9925): #0      RenderViewport.performResize.<anonymous closure> (package:flutter/src/rendering/viewport.Dart:827:15)
I/flutter ( 9925): #1      RenderViewport.performResize (package:flutter/src/rendering/viewport.Dart:880:6)
I/flutter ( 9925): #2      RenderObject.layout (package:flutter/src/rendering/object.Dart:1555:9)

前もって感謝します！

flutterflutter-layout
21
pallav bohara

この2行を追加

ListView.builder(
    scrollDirection: Axis.vertical,
    shrinkWrap: true,
...
44
BloodLoss

flexibleまたはExpandedウィジェット内にグリッドビューを配置する

return new Material(
    color: Colors.deepPurpleAccent,
    child: new Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children:<Widget>[
         Flexible(
          child:  GridView.count(crossAxisCount: _column,children: new List.generate(_row*_column, (index) {
          return new Center(
             child: new CellWidget(),
          );
        }),))]
    )
);
13
Manoj Kumar

これは通常、ListView内でGridView/Columnを使用しようとしたときに発生します。それを解決する方法はたくさんあります。

  1. ListViewをExpandedで囲む

    Column(
  children: <Widget>[
    Expanded( // wrap in Expanded
      child: ListView(...),
    ),
  ],
)

  2. ListViewをSizedBoxでラップし、バウンドheightを指定します

    Column(
  children: <Widget>[
    SizedBox(
      height: 400, // fixed height
      child: ListView(...),
    ),
  ],
)

  3. ListViewでshrinkWrap: trueを使用します。

    Column(
  children: <Widget>[
    ListView(
      shrinkWrap: true, // use this
    ),
  ],
)
10
CopsOnRoad

単一の子の配置にColumnを使用しないでください。代わりにAlignを使用してください。

    new Align(
      alignment: Alignment.topCenter,
      child: new GridView(),
    )
4
Rémi Rousselet

あなたのコラムは、どれくらいの高さがかかるかを知りません。 Flexible を使用して、主軸の利用可能なスペースを拡張および充填する柔軟性を持つようにColumnをラップします。

  @override
  Widget build(BuildContext context) {
    return new Material(
        color: Colors.deepPurpleAccent,
        child: Flexible(
            child: new Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children:<Widget>[new GridView.count(crossAxisCount: _column,children: new List.generate(_row*_column, (index) {
                  return new Center(
                      child: new CellWidget()
                  );
                }),)]
            )
        )
    );
  }
1
dmarquina