JNI calls the Java method

The method for JNI to call the Java class is similar to that of the reflected code. First obtain the object class. --> Jobject OBJ; jclass CLS = env-> getobjectclass (OBJ); then the query method is jmethodid mgetzoom = env-> getmethodid (CLS, "getzoom ","() I "); jmethodid getfocus = env-> getmethodid (CLS," getdirectionalarrows "," () ljava/util/vector ;"); then use this method ID to execute the OBJ method. Jint I = env-> callintmethod (OBJ, mgetzoom); jobject VEC = env-> callobjectmethod (OBJ, getfocus); Note the format of the getmethodid method. Jmethodid getmethodid (jnienv * ENV, jclass clazz, const char * Name, const char * sig); jnienv is not required in C ++. Clazz is the jclass. Name obtained earlier. It is the method name, and SIG is the method signature. The method signature has a specific format: (param-type) ret-type, which indicates the type of parameters passed in by the method, the following is the return type. param-type and ret-type are both composed of specific symbols. Each Java primitive type has its own corresponding symbols as shown in the following table. Table 3-2 Java VM type signatures type signature Java type Z Boolean B byte C char s short I Int J long F float D Double l fully-qualified-class; fully-qualified-class [type [] (Arg-types) ret-type method type such as long F (int n, string S, int [] ARR ); the signature of IS (iljava/lang/string; [I) J. Do not forget l fully-qualified-class; The; number following this format. PS: You can view the method signature through javap-S <class>.