java - 我是否需要释放我修改并返回的 JNI 数组？

Question

我是 JNI 的新手，在我测试的一部手机上，我收到有关 ReferenceTable 溢出 的错误。我知道这与不在 native 代码中释放 JNI/Java 项有关。

我认为我不需要释放任何东西，因为我使用给定的jfloatarray，替换它的值，然后再次返回原始的JNI对象。我认为这将使 JNI 释放对象本身，因为它只是将其取回。

JNI 代码:

extern "C"
JNIEXPORT jfloatArray JNICALL Java_methodname(
        JNIEnv *env, jobject thiz, jfloatArray data)
{
float* nativeValues = (float *)env->GetFloatArrayElements(data, 0);
doSomething(nativeValues);//overwrite the values with new values
return data;
}

JNI 错误(Android 2.3):

11-28 15:00:58.069: W/dalvikvm(833): ReferenceTable overflow (max=1024)
11-28 15:00:58.069: W/dalvikvm(833): Last 10 entries in JNI pinned array reference table:
11-28 15:00:58.069: W/dalvikvm(833):  1014: 0x405f3750 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1015: 0x405f37b0 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1016: 0x405f3810 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1017: 0x405f3870 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1018: 0x405f38d0 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1019: 0x405f3930 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1020: 0x405f3990 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1021: 0x405f39f0 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1022: 0x405f3a50 cls=[F (20 bytes)
11-28 15:00:58.069: W/dalvikvm(833):  1023: 0x405f3ab0 cls=[F (20 bytes)
11-28 15:00:58.074: W/dalvikvm(833): JNI pinned array reference table summary (1024 entries):
11-28 15:00:58.074: W/dalvikvm(833):  1020 of [F 20B (1020 unique)
11-28 15:00:58.074: W/dalvikvm(833):     4 of [F 28B (4 unique)
11-28 15:00:58.074: W/dalvikvm(833): Memory held directly by tracked refs is 20512 bytes
11-28 15:00:58.074: E/dalvikvm(833): Failed adding to JNI pinned array ref table (1024 entries)

我该怎么办？将数据值复制到新的 float* 并用它创建一个新的 jfloatarray？

Answer 1

当您通过 GetFloatArrayElements(..) 函数获取元素时，由于 JVM 将其标记为“在 native 代码中使用”，因此您需要释放数组元素。为此调用 ReleaseFloatArrayElements() 。在那里查看详细信息: http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/functions.html#wp17440