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flutter - 有没有办法让小部件等待它之前的小部件的结果

问题描述

我试图将 resultMsg 的值从 FutureBuilder 小部件传递给 Text 小部件，但它仍然给我变量的初始值，有没有办法在之前构建第一个小部件，获取变量更改（这是全局变量）并通过它？或任何其他方式来做即时消息发布我的代码以显示我要求的变量

 child: ListView(
        shrinkWrap: true,
        children: <Widget>[
          Container(
              height: 400,
              child: SafeArea(
                child: FutureBuilder(
                    future: _getdeptemp(),
                    builder: (context, snapshot) {
                      if (snapshot.hasData) {
                        int x = (snapshot.data.length);
                        double xx = double.parse(x.toString());
                       //some process
                        resultMsg = ""+Sum ; //*********here is the value I want to assign variable to it************** 
                           
                 return
                        
                         new  charts.LineChart(
                          seriesList(dataa),
                          animate: false,
                          behaviors: [
                            new charts.ChartTitle('Session number',
                                behaviorPosition:
                                    charts.BehaviorPosition.bottom,
                                //titleStyleSpec: charts.TextStyleSpec(fontSize: 14),
                                titleOutsideJustification: charts
                                    .OutsideJustification.middleDrawArea),
                            new charts.ChartTitle(
                                'Right Pose Percentage, %',
                                behaviorPosition:
                                    charts.BehaviorPosition.start,
                                //titleStyleSpec: chartsCommon.TextStyleSpec(fontSize: 11),
                                titleOutsideJustification: charts
                                    .OutsideJustification.middleDrawArea)
                          ],
                        );
                      } else {
                        return Center(child: CircularProgressIndicator());
                      }
                    }),
              )),
          Container(
             
              child: new Text(
                resultMsg,//////here is the variable ******
                style: TextStyle(
                  color: Colors.black,
                  fontSize: 16,
                ),
              )),
        ],
      ),

标签： flutterwidget

解决方案

如果你想在其他 Widget 中使用 FutureBuilder 的数据值，
那你把那个 Widget 插入到 FutureBuilder 里面怎么样？

在您的情况下，您需要通过 Column Widget 包装 LineChart 和 Container 小部件。


I just suggest but I don't know whether the error is because I don't have all source.
<As-is>
-ListView
--FutureBuilder
---LineChart
--Container
---Text

<To-be>
-ListView
--FutureBuilder
---Column
----LineChart
----Container
-----Text

or

-FutureBuilder
--ListView
---LineChart
---Container
----Text

这里是基于您的代码的建议代码，例如“To-be”。

ListView(
        shrinkWrap: true,
        children: <Widget>[
          Container(
              height: 400,
              child: SafeArea(
                child: FutureBuilder(
                    future: _getdeptemp(),
                    builder: (context, snapshot) {
                      if (snapshot.hasData) {
                        int x = (snapshot.data.length);
                        double xx = double.parse(x.toString());
                       //some process
                        resultMsg = ""+Sum ; //*********here is the value I want to assign variable to it************** 
                         return Column(
                           children: [
                            new  charts.LineChart(
                              seriesList(dataa),
                              animate: false,
                              behaviors: [
                                new charts.ChartTitle('Session number',
                                  behaviorPosition:
                                    charts.BehaviorPosition.bottom,
                                  //titleStyleSpec: charts.TextStyleSpec(fontSize: 14),
                                  titleOutsideJustification: charts
                                    .OutsideJustification.middleDrawArea),
                                new charts.ChartTitle(
                                  'Right Pose Percentage, %',
                                  behaviorPosition:
                                    charts.BehaviorPosition.start,
                                  //titleStyleSpec: chartsCommon.TextStyleSpec(fontSize: 11),
                                  titleOutsideJustification: charts
                                    .OutsideJustification.middleDrawArea)
                              ],
                            ),
                            Container(
                              child: new Text(
                                resultMsg,//////here is the variable ******
                                style: TextStyle(
                                  color: Colors.black,
                                  fontSize: 16,
                                ),
                              ),
                            ),
                          ],
                        );
                      } else {
                        return Center(child: CircularProgressIndicator());
                      }
                    }),
              )),
          
        ],
      );

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