Question

即使在指定Container GridView的高度后，我的代码也会生成方形小部件。

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<String> widgetList = ['A', 'B', 'C'];

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Container(
        child: new GridView.count(
          crossAxisCount: 2,
          controller: new ScrollController(keepScrollOffset: false),
          shrinkWrap: true,
          scrollDirection: Axis.vertical,
          children: widgetList.map((String value) {
            return new Container(
              height: 250.0,
              color: Colors.green,
              margin: new EdgeInsets.all(1.0),
              child: new Center(
                child: new Text(
                  value,
                  style: new TextStyle(fontSize: 50.0,color: Colors.white),
                ),
              ),
            );
          }).toList(),
        ),
      ),
    );
  }
}

上面代码的输出如左图所示。如何获得带有自定义高度窗口小部件的GridView，如右图所示？

Answer 1

关键是childAspectRatio。此值用于确定GridView中的布局。为了获得所需的方面，您必须将其设置为（itemWidth / itemHeight）。解决方案是：

    throw new PXSetPropertyException<CRCase.caseClassID>("Incorrect Case Class for Contract");

Answer 2

所有功劳都归功于 Github 上的 @ayRatul this answer，这是迄今为止我见过的在 GridView 中实现固定项目高度的最好和最简单的方法：

创建您自己的自定义委托：

class SliverGridDelegateWithFixedCrossAxisCountAndFixedHeight
    extends SliverGridDelegate {
  /// Creates a delegate that makes grid layouts with a fixed number of tiles in
  /// the cross axis.
  ///
  /// All of the arguments must not be null. The `mainAxisSpacing` and
  /// `crossAxisSpacing` arguments must not be negative. The `crossAxisCount`
  /// and `childAspectRatio` arguments must be greater than zero.
  const SliverGridDelegateWithFixedCrossAxisCountAndFixedHeight({
    @required this.crossAxisCount,
    this.mainAxisSpacing = 0.0,
    this.crossAxisSpacing = 0.0,
    this.height = 56.0,
  })  : assert(crossAxisCount != null && crossAxisCount > 0),
        assert(mainAxisSpacing != null && mainAxisSpacing >= 0),
        assert(crossAxisSpacing != null && crossAxisSpacing >= 0),
        assert(height != null && height > 0);

  /// The number of children in the cross axis.
  final int crossAxisCount;

  /// The number of logical pixels between each child along the main axis.
  final double mainAxisSpacing;

  /// The number of logical pixels between each child along the cross axis.
  final double crossAxisSpacing;

  /// The height of the crossAxis.
  final double height;

  bool _debugAssertIsValid() {
    assert(crossAxisCount > 0);
    assert(mainAxisSpacing >= 0.0);
    assert(crossAxisSpacing >= 0.0);
    assert(height > 0.0);
    return true;
  }

  @override
  SliverGridLayout getLayout(SliverConstraints constraints) {
    assert(_debugAssertIsValid());
    final double usableCrossAxisExtent =
        constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1);
    final double childCrossAxisExtent = usableCrossAxisExtent / crossAxisCount;
    final double childMainAxisExtent = height;
    return SliverGridRegularTileLayout(
      crossAxisCount: crossAxisCount,
      mainAxisStride: childMainAxisExtent + mainAxisSpacing,
      crossAxisStride: childCrossAxisExtent + crossAxisSpacing,
      childMainAxisExtent: childMainAxisExtent,
      childCrossAxisExtent: childCrossAxisExtent,
      reverseCrossAxis: axisDirectionIsReversed(constraints.crossAxisDirection),
    );
  }

  @override
  bool shouldRelayout(
      SliverGridDelegateWithFixedCrossAxisCountAndFixedHeight oldDelegate) {
    return oldDelegate.crossAxisCount != crossAxisCount ||
        oldDelegate.mainAxisSpacing != mainAxisSpacing ||
        oldDelegate.crossAxisSpacing != crossAxisSpacing ||
        oldDelegate.height != height;
  }
}

然后您可以像这样使用您的自定义委托：

...
GridView.builder(
            shrinkWrap: true,
            itemCount: list.length,
            gridDelegate: SliverGridDelegateWithFixedCrossAxisCountAndFixedHeight(
                crossAxisCount: 5,
                crossAxisSpacing: 5,
                mainAxisSpacing: 5,
                height: 48.0, //48 dp of height 
...

Answer 3

它为我工作。

示例代码：

var _crossAxisSpacing = 8;
var _screenWidth = MediaQuery.of(context).size.width;
var _crossAxisCount = 2;
var _width = ( _screenWidth - ((_crossAxisCount - 1) * _crossAxisSpacing)) / _crossAxisCount;
var cellHeight = 60;
var _aspectRatio = _width /cellHeight;

GridView：

         GridView.builder(
                          padding: EdgeInsets.only(
                              left: 5.0, right: 5.0, top: 10, bottom: 10),
                          shrinkWrap: false,
                          itemCount: searchList.length,
                          gridDelegate:
                              SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: _crossAxisCount,childAspectRatio: _aspectRatio),
                          itemBuilder: (context, index) {
                            final item = searchList[index];
                            return Card(
                              child: ListTile(
                                title: Text(item.name,maxLines: 1,overflow: TextOverflow.ellipsis),
                                trailing: Container(
                                  width: 15,
                                  height: 15,
                                  decoration: BoxDecoration(
                                      color: item.isActive == true
                                          ? Theme.of(context).primaryColor
                                          : Colors.red,
                                      borderRadius: BorderRadius.all(
                                          Radius.circular(50))),
                                ),
                                onTap: () {

                                },
                              ),
                              elevation: 0.5,
                            );
                          },
                        )

Answer 4

就用

 childAspectRatio: (1 / .4)

其中 1 是宽度，0.4 是高度根据您的自我定制完整代码在这里

 return GridView.count(
  crossAxisCount: 2,
  childAspectRatio: (1 / .4),
  shrinkWrap: true,
  children: List.generate(6, (index) {
    return Padding(
      padding: const EdgeInsets.all(10.0),
      child: Container(
        color: Colors.grey[600],
        child: Row(
          children: [

          ],
        ),
      ),
    );
  }),
);

Answer 5

几天前，我来这里是为了找到一种方法来动态更改从互联网加载图像时的高度，并且使用childAspectRatio不能做到这一点，因为它适用于GridView中的所有小部件（每个高度相同）。

此答案可能会帮助想要根据每个小部件内容不同的身高的人：

我找到了一个名为Flutter Staggered GridView by Romain Rastel的软件包。使用此程序包，我们可以在这里做很多事情检查示例。

要获得我们想要的东西，我们可以使用StaggeredGridView.count()及其属性staggeredTiles:，对于其值，您可以映射所有小部件并应用StaggeredTile.fit(2)。

示例代码：

StaggeredGridView.count(
    crossAxisCount: 4, // I only need two card horizontally
    padding: const EdgeInsets.all(2.0),
    children: yourList.map<Widget>((item) {
      //Do you need to go somewhere when you tap on this card, wrap using InkWell and add your route
      return new Card(
        child: Column(
          children: <Widget>[
             Image.network(item.yourImage),
             Text(yourList.yourText),//may be the structure of your data is different
          ],
        ),
      );
    }).toList(),

    //Here is the place that we are getting flexible/ dynamic card for various images
    staggeredTiles: yourList.map<StaggeredTile>((_) => StaggeredTile.fit(2))
        .toList(),
    mainAxisSpacing: 3.0,
    crossAxisSpacing: 4.0, // add some space
  ),
);

您可以找到完整的示例（复制，粘贴和运行）here。

Answer 6

crossAxisCount，crossAxisSpacing和屏幕宽度确定width，而childAspectRatio确定height。

我做了一些计算以找出它们之间的关系。

var width = (screenWidth - ((_crossAxisCount - 1) * _crossAxisSpacing)) / _crossAxisCount;
var height = width / _aspectRatio;

完整示例：

double _crossAxisSpacing = 8, _mainAxisSpacing = 12, _aspectRatio = 2;
int _crossAxisCount = 2;

@override
Widget build(BuildContext context) {
  double screenWidth = MediaQuery.of(context).size.width;

  var width = (screenWidth - ((_crossAxisCount - 1) * _crossAxisSpacing)) / _crossAxisCount;
  var height = width / _aspectRatio;

  return Scaffold(
    body: GridView.builder(
      itemCount: 10,
      itemBuilder: (context, index) => Container(color: Colors.blue[((index) % 9) * 100]),
      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: _crossAxisCount,
        crossAxisSpacing: _crossAxisSpacing,
        mainAxisSpacing: _mainAxisSpacing,
        childAspectRatio: _aspectRatio,
      ),
    ),
  );
}

Answer 7

在 GridView 中，使用以下代码：

gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 3, //Number of columns you want
childAspectRatio: (1 / .4) //height & width for the GridTile
),

如何在Flutter的GridView中设置Widget的自定义高度？

7 个答案: