Question

在更新同一setState（）中的某些先前变量之后，我需要在setState（）中运行一个方法。目前，它等待该方法完成，然后再更新页面。

（我是Flutter的新手，我的编程技能也不是很好）。

我尝试将setState（）拆分为不同的内容：

// this method is called once the animation has finished
void _solve() {
  setState(() {
    _isSolving = true; // I need to update the display here
  });

  setState(() {
    _solution = PuzzleSolver().solve(); // this takes some time and returns a map
  });

  setState(() {
    _isSolving = false; // and I need to update the display again here
  });
}

但这没有帮助，因为我真的不知道这是怎么回事。

这是简化的代码版本：

import 'package:flutter/material.dart';
import './puzzleSolver.dart';

class SomePage extends StatefulWidget {
  @override
  _SomePageState createState() => _SomePageState();
}

class _SomePageState extends State<SomePage> with TickerProviderStateMixin {
  AnimationController animationController;
  Map _solution = {};
  bool _isSolving = false;

  void initState() {
    super.initState();
    animationController = AnimationController(
        vsync: this, duration: Duration(seconds: 5))
      ..addStatusListener(
          (state) => (state == AnimationStatus.dismissed) ? _solve() : null); // run _solve() once the animation has finished
    animationController.reverse();
  }

  // this method is called once the animation has finished
  void _solve() {
    setState(() {
      _isSolving = true; // I need to update the display here
      _solution = PuzzleSolver().solve(); // this takes some time and returns a map
      _isSolving = false; // and I need to update the display here again
    });

    // at the moment it updates the display here
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Some Page'),
      ),
      body: Column(
        children: <Widget>[
          (_isSolving == false && _solution.isEmpty)
              ? Text('hello world') // only show when it's not solving and there is no solution
              : RaisedButton(
                  child: Text('show solution'),
                  onPressed: (_isSolving)
                      ? null // disable the button when its solving
                      : () {}, // enable it when its solved
                ),
          AnimatedBuilder(
            animation: animationController,
            builder: (BuildContext context, Widget child) {
              return Container(); // this is where the animated widgets would be
            }
          ),
        ],
      ),
    );
  }
}

Answer 1

假设PuzzleSolver().solve()方法是Future，则可以执行以下操作：

void _solve() async{
  setState(() {
    _isSolving = true; 
  });

  _solution = await PuzzleSolver().solve(); // waits for the future to finish

  setState(() {
    _isSolving = false; 
  });

Flutter：在setState（）中运行方法之前更新页面

1 个答案: