Flutter：如何修复 FutureBuilder 中由 setState 引起的错误

如何解决Flutter：如何修复 FutureBuilder 中由 setState 引起的错误

我的目标是在单击 ExpansionTile 时加载一次 Future 并存储值，以便在 Tile 关闭然后重新打开时不会再次加载 Future。

我当前代码的问题是这个错误：

uint64_t minimumPasses(uint64_t m,uint64_t w,uint64_t p,uint64_t n) {    
    if ((n / m) <= w) {
        return 1;
    }
    
    uint64_t currentProductionStorage = 0;
    uint64_t minRounds = std::numeric_limits<uint64_t>().max();
    uint64_t currentRounds = 0;
    uint64_t currentProductionSpeed;
    
    while (true) {      
        currentRounds++; 
        currentProductionSpeed = m * w;
        currentProductionStorage += currentProductionSpeed;
        uint64_t roundsWithoutFurtherInvest = 0;
        if (n >= currentProductionStorage) {
            roundsWithoutFurtherInvest = (n + currentProductionSpeed - 1 - currentProductionStorage) / (currentProductionSpeed);    
        }
        
        if (minRounds < currentRounds + roundsWithoutFurtherInvest) {
            break;    
        }
        minRounds = currentRounds + roundsWithoutFurtherInvest;
        
        if (currentProductionStorage < p) {
            uint64_t roundsBeforeInvest = (p + currentProductionSpeed - 1 - currentProductionStorage) / currentProductionSpeed;
            currentProductionStorage += (roundsBeforeInvest * m * w);
            currentRounds += roundsBeforeInvest;
        }
        
        uint64_t numOfPurchasedUnits = currentProductionStorage / p;
        currentProductionStorage %= p;
        
        uint64_t diff = std::llabs(w - m);
        uint64_t part1 = numOfPurchasedUnits; 
        uint64_t part2 = 0;
        if (diff < numOfPurchasedUnits) {
            uint64_t remainingPurchasedUnits = numOfPurchasedUnits - diff; 
            part1 = diff + (remainingPurchasedUnits / 2);
            part2 = (remainingPurchasedUnits / 2) + (remainingPurchasedUnits % 2);
        }
        
        if (m > w) {
            w += part1;
            m += part2;
        } else {
            m += part1;
            w += part2;
        }
    }
    
    return minRounds;
}

我知道错误是关于什么的，但我不知道如何修复它。这是我当前的代码：

I/flutter (30528): The following assertion was thrown building FutureBuilder<Trim>(dirty,state:
I/flutter (30528): _FutureBuilderState<Trim>#90a6d):
I/flutter (30528): setState() or markNeedsBuild() called during build.
I/flutter (30528): This Dashboard widget cannot be marked as needing to build because the framework is already in the
I/flutter (30528): process of building widgets.  A widget can be marked as needing to be built during the build phase
I/flutter (30528): only if one of its ancestors is currently building. This exception is allowed because the framework
I/flutter (30528): builds parent widgets before children,which means a dirty descendant will always be built.
I/flutter (30528): Otherwise,the framework might not visit this widget during this build phase.
I/flutter (30528): The widget on which setState() or markNeedsBuild() was called was:
I/flutter (30528):   Dashboard
I/flutter (30528): The widget which was currently being built when the offending call was made was:
I/flutter (30528):   FutureBuilder<Trim>

解决方法

您以后不能使用 setstate 或流构建器只需删除 setstate