如何对新通知进行分类和分组-Flutter

Question

我遇到困难，但是我发现很难根据刚刚输入的通知对通知进行分组。因此目标是可以在顶部看到刚到达的通知。用于新通知的标记为“ NEW”，在这里我使用ListView对数据进行排序。这是用户买卖和聊天时的通知页面。关键是如何根据新通知设置正确的位置并对数据进行排序

Widget widget_purchase() {
return new Expanded(
  child: RefreshIndicator(
    onRefresh: () async {
      pagePurchase = 1;
      await getDataPurchase();
      pagePurchase = 2;
      return true;
    },
    child: LoadMore(
      isFinish: lastPurchase == 0,
      whenEmptyLoad: true,
      textBuilder: DefaultLoadMoreTextBuilder.english,
      onLoadMore: () async {
        await getDataPurchase();
        pagePurchase += 1;
        return true;
      },
      child: ListView.builder(
        itemCount: _purchase.length,
        scrollDirection: Axis.vertical,
        shrinkWrap: true,
        itemBuilder: (context, index) {
          return new Padding(
            padding: EdgeInsets.fromLTRB(15, 5, 0, 0),
            child: new GestureDetector(
              onTap: () {
                Navigator.pushNamed(
                  context, '/purchase_page',
                  arguments: _purchase[index]['id']
                ).then((val) async {
                    pagePurchase = 1;
                    await getDataPurchase();
                    pagePurchase = 2;
                });
                idPurchase = _purchase[index]['id'];
                patchUpdatePurchase();
              },
              child: new Container(
                //height: 100,
                decoration: new BoxDecoration(
                  borderRadius: new BorderRadius.circular(8.0),
                ),
                width: MediaQuery.of(context).size.width,
                child: new Row(
                  crossAxisAlignment : CrossAxisAlignment.start,
                  children: <Widget>[
                    new Padding(
                      padding: EdgeInsets.fromLTRB(10, 0, 5, 0),
                      child: new FadeInImage.assetNetwork(
                        placeholder: "",
                        height: 70,
                        width: 100,
                        fit: BoxFit.fill,
                        image: _purchase[index]['filePath'][0],
                      ),
                    ),
                    new Flexible(
                      child: new Padding(
                        padding: EdgeInsets.only(top: 2),
                        child: new Column(
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: <Widget>[
                            new Row(
                              children : <Widget>[
                                Flexible(
                                  child: new Padding(
                                    padding: EdgeInsets.fromLTRB(5, 0, 0, 0),
                                    child: new Text(
                                      _purchase[index]['game_title'],
                                      overflow: TextOverflow.ellipsis,
                                      maxLines: 2,
                                      style: new TextStyle(
                                        fontSize: 14,
                                        fontWeight: FontWeight.bold,
                                        color: selectedColor,
                                      ),
                                    ),
                                  ),
                                ),
                                _purchase[index]['isRead'] == false ? 
                                new Padding(
                                  padding: EdgeInsets.only(left: 5),
                                  child: new Container(
                                    child: new Icon(
                                      Icons.fiber_new,
                                      color: selectedColor,
                                    ),
                                  ),
                                )
                                : new SizedBox.shrink(),
                              ],
                            ),
                            new Padding(
                              padding: EdgeInsets.fromLTRB(5, 0, 0, 0),
                              child: new Text(
                                _purchase[index]['product_type_name'],
                                overflow: TextOverflow.ellipsis,
                                style: new TextStyle(fontSize: 12),
                              ),
                            ),
                            new Row(
                              children: <Widget>[
                                new Padding(
                                  padding: EdgeInsets.fromLTRB(5, 0, 0, 0),
                                  child: new Text(
                                    'US\$',
                                    style: new TextStyle(fontSize: 12),
                                  ),
                                ),
                                new Flexible(
                                  child: new Text(
                                    " " + _purchase[index]['amount'].toString(),
                                    style: new TextStyle(fontSize: 12),
                                    overflow: TextOverflow.ellipsis,
                                  ),
                                ),
                              ],
                            ),
                            new Padding(
                              padding: EdgeInsets.fromLTRB(5, 0, 0, 0),
                              child: new Text(
                                _purchase[index]['status'],
                                style: new TextStyle(fontSize: 12),
                              ),
                            ),
                          ],
                        ),
                      ),
                    ),
                  ],
                ),
              ),
            ),
          );
        },
      ),
    ),
  ),
);}

Answer 1

假定您具有新通知的属性。例如：status：

purchases.sort((a, b) => a["status"].compareTo(b["status"])); // if list contains model: a.status

将所有值添加到purchases列表后，只需在行上方调用，并注意List的{​​{3}}不会返回任何内容。

Answer 2

据我了解，您希望所有新购买商品都位于顶部。其余部分要低于新购买的产品。

在构建窗口小部件之前，您可以基于_purchase对isRead进行排序。如果isRead属性为false，请给其较低的排序顺序，使其升序显示为较高。

Widget widget_purchase() {
   _purchase.sort((a, b) => (b['isRead']? 1 : 0) - (a['isRead']? 1 : 0));

   //Your code....
}