android - GetFieldID 在 Android 4.4 及更早版本上失败

Question

我想使用 dlib 库进行人脸检测，但它不适用于旧手机。

我因以下堆栈跟踪而崩溃:

E/AndroidRuntime( 4288): FATAL EXCEPTION: pool-1-thread-1
E/AndroidRuntime( 4288): java.lang.ExceptionInInitializerError
E/AndroidRuntime( 4288):    at com.tzutalin.dlibtest.MainActivity.runDetectAsync(MainActivity.java:235)
E/AndroidRuntime( 4288):    at com.tzutalin.dlibtest.MainActivity_.access$301(MainActivity_.java:34)
E/AndroidRuntime( 4288):    at com.tzutalin.dlibtest.MainActivity_$6.execute(MainActivity_.java:158)
E/AndroidRuntime( 4288):    at org.androidannotations.api.BackgroundExecutor$Task.run(BackgroundExecutor.java:405)
E/AndroidRuntime( 4288):    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:442)
E/AndroidRuntime( 4288):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
E/AndroidRuntime( 4288):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
E/AndroidRuntime( 4288):    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:150)
E/AndroidRuntime( 4288):    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:264)
E/AndroidRuntime( 4288):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
E/AndroidRuntime( 4288):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
E/AndroidRuntime( 4288):    at java.lang.Thread.run(Thread.java:856)
E/AndroidRuntime( 4288): Caused by: java.lang.NoSuchFieldError: no field with name='mLabel' signature='java/lang/String' in class Lcom/tzutalin/dlib/VisionDetRet;
E/AndroidRuntime( 4288):    at com.tzutalin.dlib.PeopleDet.jniNativeClassInit(Native Method)
E/AndroidRuntime( 4288):    at com.tzutalin.dlib.PeopleDet.<clinit>(PeopleDet.java:42)
E/AndroidRuntime( 4288):    ... 12 more

因此，C 代码如下所示:

void JNIEXPORT DLIB_JNI_METHOD(jniNativeClassInit)(JNIEnv* env, jclass _this) {
  jclass detRetClass = env->FindClass("com/tzutalin/dlib/VisionDetRet");
  CHECK_NOTNULL(detRetClass);
  gVisionDetRetOffsets.label =
      env->GetFieldID(detRetClass, "mLabel", "java/lang/String");
  gVisionDetRetOffsets.confidence =
      env->GetFieldID(detRetClass, "mConfidence", "F");
  gVisionDetRetOffsets.left = env->GetFieldID(detRetClass, "mLeft", "I");
  gVisionDetRetOffsets.top = env->GetFieldID(detRetClass, "mTop", "I");
  gVisionDetRetOffsets.right = env->GetFieldID(detRetClass, "mRight", "I");
  gVisionDetRetOffsets.bottom = env->GetFieldID(detRetClass, "mBottom", "I");
  gVisionDetRetOffsets.addLandmark =
      env->GetMethodID(detRetClass, "addLandmark", "(II)Z");
  if (gVisionDetRetOffsets.addLandmark == NULL) {
    LOG(FATAL) << "Can't Find Method addLandmark(int,int)";
  }
  LOG(INFO) << "JniNativeClassIni Success";
}

以及相关的 Java 类:

public final class VisionDetRet {
    private String mLabel;
    private float mConfidence;
    private int mLeft;
    private int mTop;
    private int mRight;
    private int mBottom;
    private ArrayList<Point> mLandmarkPoints = new ArrayList<>();

    VisionDetRet() {
    }

    // Other code
}

因此，字段显然在这里，并且它获取类(CHECK_NOTNULL(detRetClass) 成功)。那么为什么它会在旧手机上崩溃呢？ Google 帮不上什么忙，而且我对 NDK/JNI 的东西还很陌生。

P. S.Java文件是here C文件是here (是的，它们在 2 个不同的 repo 协议(protocol)中)

Answer 1

我不确定这对您在任何 Android 版本上的效果如何，因为 java/lang/String 是 GetFieldID 的错误签名。

对于类，签名应该是 L fully-qualified-class ;，所以在你的情况下你需要 Ljava/lang/String;