Question

我正在尝试找出一种方法来指示FutureBuilder完成加载时向周围的类指示。 RefreshIndicator将Future作为参数，并在Future完成时停止显示刷新指示符。我无权访问传递给Future的完全相同的FutureBuilder变量，尤其是当它们在两个单独的类中时，除非我可以传递对一个的引用以及它在其他课程，我会知道...

Answer 1

我也在寻找这个答案。终于我明白了...

这是我的工作方式

FutureBuilder<String>(
  future: _calculation, // a previously-obtained Future<String> or null
  builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
    switch (snapshot.connectionState) {
      case ConnectionState.none:
        return Text('Press button to start.');
      case ConnectionState.active:
      case ConnectionState.waiting:
        return Text('Awaiting result...');
      case ConnectionState.done:
        if (snapshot.hasError)
          return Text('Error: ${snapshot.error}');
        return  new RefreshIndicator(
                    key: _refreshIndicatorKey,
                    color: Colors.blue,
                    onRefresh: () {
                    setState(() {
                       _calculation= getCalculation();
                     });
                   },
                   child: SingleChildScrollView( // if u are using Listview remove SingleChildScrollView 
                          physics: AlwaysScrollableScrollPhysics(), 
                          child: Text('Result: ${snapshot.data}')
                   )
               );
    }
    return null; // unreachable
  },
) //FutureBuilder

   Future<String> getCalculation() async {
     /*Write your API here or what ever u want to get when pull to refresh*/

    return null;

   }

Answer 2

您必须访问快照，前提是builder参数：

因此，snapshot.data为您带来未来。

new FutureBuilder<String>(
  future: _calculation, // a Future<String> or null
  builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
    switch (snapshot.connectionState) {
      case ConnectionState.none: return new Text('Press button to start');
      case ConnectionState.waiting: return new Text('Awaiting result...');
      default:
        if (snapshot.hasError)
          return new Text('Error: ${snapshot.error}');
        else
          return new Text('Result: ${snapshot.data}');
    }
  },
)

示例：https://flutter.io/cookbook/networking/background-parsing/

文档：https://docs.flutter.io/flutter/widgets/FutureBuilder-class.html

如何在Flutter中将RefreshIndicator与FutureBuilder一起使用？

2 个答案: