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，我发现了关于ReferenceTable overflow的错误。我理解这与不在本机代码中释放JNI/Java项有关。

我认为我不需要发布任何东西，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。我以为这会使JNI释放对象本身，因为它只会得到它。

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(Android2.3)：

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*并创建一个新的jfloatarray？

Answer 1

当您通过GetFloatArrayElements(..)函数获得元素时，您需要释放数组元素，因为JVM将其标记为“在本机代码中使用”。打电话给ReleaseFloatArrayElements()。查看详细信息：http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/functions.html#wp17440