Android 在简单颤振应用程序中使用列中的GridView的问题

我最近开始学习颤振，因此正在构建一个我称之为“Basketly”的教学应用程序

UIs结构非常简单：

     @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('Basketly - dein Einkauf'),
          actions: <Widget>[
            new FlatButton.icon(
              label: new Text("Einstellungen"),
              onPressed: () {
                /*nav to settings */
                Navigator.push(context,
                    MaterialPageRoute(builder: (context) => SettingsView()));
              },
              icon: new Icon(Icons.settings),
            ),
          ],
        ),
        body: new Column(
          mainAxisSize: MainAxisSize.max,
            children: <Widget>[
          new Text(
            "Einkaufswagen",
            style: new TextStyle(
                fontSize: 12.0,
                color: Colors.amber,
                fontWeight: FontWeight.w600,
                fontFamily: "Roboto"),
          ),

          Expanded(
            child: new GridView.count(
                crossAxisCount: 6,
                children: this.widget.basketItems,
              ),
          ),

          new Divider(color: Colors.grey),
          new Text(
            "Produkte",
            style: new TextStyle(
                fontSize: 12.0,
                color: Colors.amber,
                fontWeight: FontWeight.w600,
                fontFamily: "Roboto"),
          ),

      new GridView.count(
                crossAxisCount: 6,
                children: this.widget.allItems,
                shrinkWrap: true),


          new Divider(color: Colors.grey),

          //TODO here we input some expandeable gridviews or something

          new MetaProdCategory("Reinigungsmittel"),
          new MetaProdCategory("Getränke"),
          new MetaProdCategory("Obst"),
          new MetaProdCategory("Milch & Käse"),
          new MetaProdCategory("Gemüse"),


          new Row( children: <Widget>[
            new Switch(onChanged: switchChanged, value: false),
            new Text("Vegan"),
            new Switch(onChanged: switchChanged, value: false),
            new Text(
              "Bio",
            ),
            new Switch(onChanged: switchChanged, value: false),
            new Text(
              "Regional",
            ),
            new Switch(onChanged: switchChanged, value: false),
            new Text(
              "Fair",
            ),
          ]),
        ]));

…包括一些日志记录，以确保一切正常工作：

log("---------basketItems:");
this.widget.basketItems.forEach((element) {
  log(element.stringify());
});
log("----------allItems:");
this.widget.allItems.forEach((element) {
  log(element.stringify());
});

[log] you tapped on Brot
[log] addToBasket called
[log] ---------basketItems:
[log] Brot true
[log] ----------allItems:
[log] Bier false
[log] Senf false
[log] Lauch false
[log] Steak false
[log] Bergkäse false
[log] Mehl false
[log] Kürbis false
[log] Oliven false
[log] Pfeffer false

现在开始解决问题

当我标记其中一个ProdCategories（本例中为Brot）时，根据日志，一切都按预期工作：

log("---------basketItems:");
this.widget.basketItems.forEach((element) {
  log(element.stringify());
});
log("----------allItems:");
this.widget.allItems.forEach((element) {
  log(element.stringify());
});

[log] you tapped on Brot
[log] addToBasket called
[log] ---------basketItems:
[log] Brot true
[log] ----------allItems:
[log] Bier false
[log] Senf false
[log] Lauch false
[log] Steak false
[log] Bergkäse false
[log] Mehl false
[log] Kürbis false
[log] Oliven false
[log] Pfeffer false

正如您所看到的，Brot现在驻留在basketItems中，并从allItems中删除—正如预期的那样

…但不知何故，UI在Einkaufswagen GridView中没有显示Brot。

我不知道我做错了什么，因为几个小时没有成功，我一直在解决这个问题。 在GridView周围的Flitter中似乎有很多bug，特别是在专栏中使用时——但我怀疑对于我所需要的可用性必须有一个合适的解决方案

这个怎么样

new GridView.builder(
    itemBuilder: (BuildContext context, int index) {
      return this.widget.basketItems[index];
    },
    gridDelegate: new SliverGridDelegateWithFixedCrossAxisCount(
      crossAxisCount: 2,
    ),
    itemCount: this.widget.basketItems.length,
    shrinkWrap: true),

及

---

你可以使用“GridView.builder”而不是“GridView.count”。我的朋友做得很好！一个问题：为什么它会起作用？你认为以前的问题是什么。。。如何避免这样的情况，即没有预防性地抛出错误/警告？您好，Gewure，“GridView.count”是横轴上固定数量的平铺。“GridView.builder”是根据需要创建的。请参阅

new GridView.builder(
    itemBuilder: (BuildContext context, int index) {
      return this.widget.allItems[index];
    },
    gridDelegate: new SliverGridDelegateWithFixedCrossAxisCount(
      crossAxisCount: 6,
    ),
    itemCount: this.widget.allItems.length,
    shrinkWrap: true),