将精度与 Float.MAX_VALUE 进行比较意味着什么？

Question

在阅读 有关位置的 Android 开发者博客文章时, 我遇到了这段代码（从博客中剪切和粘贴）：

List<String> matchingProviders = locationManager.getAllProviders();
for (String provider: matchingProviders) {
  Location location = locationManager.getLastKnownLocation(provider);
  if (location != null) {
    float accuracy = location.getAccuracy();
    long time = location.getTime();

    if ((time > minTime && accuracy < bestAccuracy)) {
      bestResult = location;
      bestAccuracy = accuracy;
      bestTime = time;
    }
    else if (time < minTime && 
         bestAccuracy == Float.MAX_VALUE && time > bestTime){
      bestResult = location;
      bestTime = time;
    }
  }
}

虽然其余部分非常清楚，但这一行让我难住了：

    else if (time < minTime && 
         bestAccuracy == Float.MAX_VALUE && time > bestTime){

“时间”必须在可接受的延迟期内&比之前的 bestTime 更新。这是有道理的。

但是 bestAccuracy 与 Max Float 值的比较意味着什么？什么时候精度会完全等于浮点数可以容纳的最大值？

Answer 1

如果您按照他的链接访问整个源文件，那么该特定位会更有意义。这是一个稍微大一点的代码片段：

Location bestResult = null;
float bestAccuracy = Float.MAX_VALUE;
long bestTime = Long.MIN_VALUE;

// Iterate through all the providers on the system, keeping
// note of the most accurate result within the acceptable time limit.
// If no result is found within maxTime, return the newest Location.
List<String> matchingProviders = locationManager.getAllProviders();
for (String provider: matchingProviders) {
  Location location = locationManager.getLastKnownLocation(provider);
  if (location != null) {
    float accuracy = location.getAccuracy();
    long time = location.getTime();

    if ((time > minTime && accuracy < bestAccuracy)) {
      bestResult = location;
      bestAccuracy = accuracy;
      bestTime = time;
    }
    else if (time < minTime && bestAccuracy == Float.MAX_VALUE && time > bestTime) {
      bestResult = location;
      bestTime = time;
    }
  }
}

非常简单，Float.MAX_VALUE 是他的 bestAccuracy 的默认值，他只是检查他在前面的 if 中是否没有减少它 子句。

Answer 2

我猜测 bestAccuracy 已初始化为 Float.MAX_VALUE。如果是这样，代码看起来可以总结为：找到精度最小（最好？）且时间大于 minTime 的提供者。如果没有大于minTime的时间，则取最接近minTime的时间。

可以将其重构

    if ((time < minTime && accuracy < bestAccuracy)) {
      bestResult = location;
      bestAccuracy = accuracy;
      bestTime = time;
    }
    else if (time > minTime && bestAccuracy == Float.MAX_VALUE && time < bestTime) {
      bestResult = location;
      bestTime = time;
    }

为

    if ((time < minTime && accuracy < bestAccuracy)) {
      bestResult = location;
      bestAccuracy = accuracy;
      bestTime = time;
      foundWithinTimeLimit = true;
    }
    else if (time > minTime && !foundWithinTimeLimit && time < bestTime) {
      bestResult = location;
      bestTime = time;
    }

使其更加清晰。