为什么通过JNI在Java和C ++之间传递不正确的值？

Question

I want to pass a double value from C++ to Java (Android) using JNI.

Relevant C++ code:

JNIEXPORT jdouble JNICALL
Java_test_MPEG_DASH_ffmpeg_PlayerUI_Notif(JNIEnv* env, jobject obj,jint st){

    jdouble p=receiver->buffer->Notify();
    LOGI("Notifyyyyyyyyy from jni is %d ",p);
    return p;
}

Displays 35, 36, etc

When accessed in Java by calling the native method, the wrong values are returned: 0.0000133333

Relevant Java code:

double buf=Notify();
Log.d(TAG, "Bufffffffffffffffffffffffffer :"+buf" ms");

Why are the values inconsistent?

Answer 1

"%d" is not a format specifier compatible with floating point types. If you use it, you will force a misinterpretation of the bits comprising the jdouble, and print an incorrect value.

It's likely that the value returned to Java is correct (there's a fair amount of type enforcement there), and that being logged incorrect.