java - 安卓相机: Unboxing of 'characteristics.get(CameraCharacteristics.LENS_FACING)' may produce NPE

Question

我正在实现Camera2，当我设置相机输出时，我收到以下警告(我无法重现可能发生的任何“npe”)(我从 google 的示例中获取代码)以下行给出以下警告:

"Unboxing of 'characteristics.get(CameraCharacteristics.LENS_FACING)' may produce NPE."

 for (String cameraId : manager.getCameraIdList()) {
      CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);

      if (characteristics.get(CameraCharacteristics.LENS_FACING) 
           == CameraCharacteristics.LENS_FACING_FRONT) { //THESE LINE IS WHERE THE WARNING APPEARS
           continue;
         }
   ....

是否有人知道如何以正确的方式检查此情况，以便在发生这种情况时捕获此情况？

Answer 1

您将其与原始int进行比较，并且characteristics.get(CameraCharacteristics.LENS_FACING)可能返回一个Integer，它是目的。发生的事情是你将拥有

Integer integer = characteristics.get(CameraCharacteristics.LENS_FACING);
if (integer.intValue() == CameraCharacteristics.LENS_FACING_FRONT) {

}

如果integer为空，您将获得一个NPE访问intValue()