Flutter计算百分比报错Unsupported operation: Infinity or NaN toInt

我需要计算一个数值的百分比，部分场景下除法运算的分子可能为0。在Flutter中实现相关逻辑后，偶尔会抛出错误：Unsupported operation: Infinity or NaN toInt，热重载后有时能得到预期结果，但再次重载时问题会重复出现。我先尝试判断percentage是否为NaN或无穷大，之后又添加了判断totalDriver是否为0的逻辑，但问题依然存在，请问这是什么原因？

相关代码 #

int? totalDriver = 0;
final totalCompleted = snapshot.data;//I got this from streamBuilder and everything is perfect here.
final percentage = ((totalCompleted! / totalDriver!) * 100).floor();//The starts from here. So I brought this logic.
if (percentage.isNaN || percentage.isInfinite) {
              return Row(
                children: [
                  SizedBox(
                    width: screenWidth * 0.4,
                    child: Text(
                      "$completedString:",
                      style: const TextStyle(color: Colors.green),
                    ),
                  ),
                  Text("$totalCompleted     (0%)"),
                ],
              );
            }else {return...}
//I also later added this logic (So in case the denominator id 0, the percentage will be infinity, so if it's infinity it should return (0%))but it still persists.
if (totalDriver == 0) {
              return Row(
                children: [
                  SizedBox(
                    width: screenWidth * 0.4,
                    child: Text(
                      "$completedString:",
                      style: const TextStyle(color: Colors.green),
                    ),
                  ),
                  Text("$totalCompleted     (0%)"),
                ],
              );
            } else {return...}

核心问题是你的判断逻辑写在了百分比计算之后：

• 当totalDriver为0时，执行totalCompleted! / totalDriver!会得到Infinity，紧接着调用.floor()方法时，会直接触发Unsupported operation: Infinity or NaN toInt异常——此时你的判断代码还没来得及执行，程序就已经报错了。
• 另外，你写的两个判断是顺序执行的，第一个判断如果触发return，第二个判断根本不会运行；但最关键的还是计算步骤先于判断，导致异常提前抛出。

把判断逻辑提前到百分比计算之前，先处理分母为0的情况，再执行计算：

int? totalDriver = 0;
final totalCompleted = snapshot.data;

// 先处理分母为0或数据为空的边界情况
if (totalDriver == 0 || totalCompleted == null) {
  return Row(
    children: [
      SizedBox(
        width: screenWidth * 0.4,
        child: Text(
          "$completedString:",
          style: const TextStyle(color: Colors.green),
        ),
      ),
      Text("${totalCompleted ?? 0}     (0%)"),
    ],
  );
}

// 分母合法时再计算百分比
final percentage = ((totalCompleted / totalDriver) * 100).floor();

// 额外做一层安全判断，防止其他异常情况
if (percentage.isNaN || percentage.isInfinite) {
  return Row(
    children: [
      SizedBox(
        width: screenWidth * 0.4,
        child: Text(
          "$completedString:",
          style: const TextStyle(color: Colors.green),
        ),
      ),
      Text("$totalCompleted     (0%)"),
    ],
  );
}

// 正常情况返回对应UI
return ...;

额外提示：代码中你用!强制解包totalCompleted，如果snapshot.data可能为null，会引发空指针异常，建议一起加入null判断（如上代码所示）。

内容的提问来源于stack exchange，提问作者EBENEZER OCANSEY