Parameter conversion between Java and C

1: returns a string in C.
...................
(* Env)-> newstringutf (ENV, "Zhongguo China ");
...................

2: C returns an array.
.....................
Int I = 0;
Jintarray array;
Array = (* env)-> newintarray (ENV, 10 );
For (; I <10; I ++)
{
(* Env)-> setobjectarrayelement (ENV, array, I, I * 2 );
}
Return array;

3: In C, the input parameter called is array, which is the input array.
.........
Int sum = 0, I;
Int Len = (* env)-> getarraylength (ENV, array );
Jint * element = (* env)-> getintarrayelement (ENV, array, 0 );
For (I = 0; I <Len; I ++)
{
Sum + = * (element + I );
}
Return sum;

4: In C, calling methods of classes in Java has no parameters. Only the return value is string.
@ "() Ljava/lang/string;" indicates that if the parameter is null, the returned value is of the string type.
Jniexport jstring jnicall {
Tagshow (Event)
} "> Java_tao_hai_bing_demo_getcallback (jnienv ENV, jobject object ){

Jmethodid mid;
Jclass CLS = (* env)-> findclass (ENV, "Tao/HAI/Bing/demo"); // package name + class name
Mid = (* env)-> getmethodid (ENV, CLS, "Callback", "() ljava/lang/string;"); // method name in callback Java
Jstring MSG = (* env)-> callobjectmethod (ENV, object, mid); // pay attention to the jobject passed by JNI.
Return MSG;
}

5: Calling static methods of classes in Java in C without parameters, only return values: String
@ "() Ljava/lang/string;" indicates that if the parameter is null, the returned value is of the string type.
Jniexport jstring jnicall java_tao_hai_bing_demo_getcallback (jnienv ENV, jobject object ){

Jmethodid mid;
Jclass CLS = (* env)-> findclass (ENV, "Tao/HAI/Bing/demo"); // package name + class name
Mid = (* env)-> gestatictmethodid (ENV, CLS, "Callback", "() ljava/lang/string;"); // method name in callback Java
Jstring MSG = (* env)-> callstaticobjectmethod (ENV, CLS, mid); // note that the jobject passed by JNI
Return MSG;
}

6: Call methods in Java in C. Two parameters. The first parameter is int. The second parameter is string. the return value is string.
@ "(Iljava/lang/string;) ljava/lang/string" indicates that the parameter is the first parameter, and the second parameter is the integer parameter. The return value of string is the string parameter.
Jniexport jstring jnicall java_tao_hai_bing_demo_getcallback (jnienv ENV, jobject object ){

Jmethodid mid;
Jclass CLS = (* env)-> findclass (ENV, "Tao/HAI/Bing/demo"); // package name + class name
Mid = (* env)-> gestatictmethodid (ENV, CLS, "Callback", "(iljava/lang/string;) ljava/lang/string ;"); // method name in callback Java
Jstring Param = (* env)-> newstringutf (ENV, "taohaibing ");
Jstring MSG = (* env)-> callstaticobjectmethod (ENV, CLS, mid, 22, Param); // The jobject passed by JNI
Return MSG;
}

8: calling global variables in Java in C
Jclass CLS = (* env)-> findclass (ENV, "Tao/HAI/Bing/demo ");
Jfieldid id = (* env)-> getfieldid (ENV, CLS, "num", "I"); // If num is the variable I in Java, the type of the variable is integer.
Jint Param = (* env)-> getintfield (ENV, object, ID );

Jfieldid Id2 = (* env)-> getfieldid (ENV, CLS, "num2", "ljava/lang/string "); // num2 is the variable I in Java, which indicates that the variable type is string.
Jstring Param = (* env)-> getobjectfield (ENV, object, ID );

8: Call static variables in Java in C
Jclass CLS = (* env)-> findclass (ENV, "Tao/HAI/Bing/demo ");
Jfieldid id = (* env)-> getstaticfieldid (ENV, CLS, "num", "ljava/lang/string "); // If num is the variable I in Java, the type of the variable is integer.
Jstring Param = (* env)-> gestaticobjectfield (ENV, CLS, ID );