Flutter Await不等待

本文介绍了Flutter Await不等待的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

为什么在进入打印语句之前，程序不等待函数返回列表?

Why won't the program wait for the function to return the list before going to the print statement?

我认为这是因为我使forEach循环异步，但是我需要使其异步才能获得newSummary，这是一个Future.

I think it's because I made the forEach loop async but I need it to be async to get the newSummary which is a Future.

Future syncToCloud() async{ final List<Map<String,dynamic>> _events = await events(); print(_events.length); } Future<List<Map<String, dynamic>>> events() async { List<Map<String, dynamic>> maps = await db.query('data'); List<Map<String, dynamic>> newMaps=[]; maps.forEach((element)async{ Map<String, dynamic> newElement = {}; if(element['summary']!=''){ newElement['summary'] = await newSummary(element['summary']); print(newElement['summary']); } else{ newElement['summary'] = element['summary']; } newMaps.add(newElement); }); return newMaps; } void main()async{ await syncToCloud(); }

推荐答案

您正在不起作用的回调中执行返回[{'hi':5}] .您应该等待Future.delayed，然后像这样返回列表 await Future.delayed(Duration(seconds:2)); .

You're executing your return [{'hi':5}] in a callback which wouldn't work. You should await the Future.delayed then return the List like this await Future.delayed(Duration(seconds: 2));.

Future syncToCloud() async{ final List<Map<String,dynamic>> _events = await events(); print(_events.length); } Future<List<Map<String, dynamic>>> events() async { await Future.delayed(Duration(seconds: 2)); return [{'hi':5}]; } void main()async{ await syncToCloud(); }