![]() Member variable signature for a String variable, such as c.s The object, and terminated by a semicolon ( ). The signature for a Java object, such as a String,īegins with the letter L, followed by the fully-qualified class for Member variable with "D", a boolean member variable with "Z", and so on. Represent an integer member variable with "I", a float member variable with "F", a double The member variable symbols are the sameĪs the argument symbols in the method signature. Member variable, enclosed in double quotes (""). The member variable signature is the encoded symbol for the type of the Specify member variable signatures following the sameĮncoding scheme as method signatures. The class from which it is derived is unloaded. Similar to method IDs, a member variable ID remains valid until The member variable ID uniquely identifies a member variable inĪ given class. First we obtain the member variable ID, then use the member variable ID to access the member variable itself. Just as we did when calling a Java method, we factor out the cost of member variable lookup Jstr = (*env)->GetObjectField(env, obj, fid) We use the function GetObjectField to get the value of the instance string member variable s: Si = (*env)->GetStaticIntField(env, cls, fid) For example, in FieldAccess.c, we use GetStaticIntField to get the value of the class integer member variable si, as follows: To get the value of an instance member variable, pass the object to the appropriate instance member variable accessįunction. To get the value of a class member variable, pass the class to one of the appropriate class member variableĪccess functions. ![]() Specified by the member variable identifier. Use one of several JNI functions to either get or set the member variable.For example, in FieldAccess.c, we get the identifier for the class integer member variable si as follows:įid = (*env)->GetStaticFieldID(env, cls, "si", "I") Īnd we get the identifier for the instance string member variable s as follows:įid = (*env)->GetFieldID(env, cls, "s", "Ljava/lang/String ") Obtain the identifier for that member variable from its class, name,Īnd type signature.To get and set Java member variables from a native language method, you must do the following: ![]() Procedure for Accessing a Java Member Variable Have indeed changed, we print out their values again in the Java application after Member variables and then sets the member variables to new values. The example program calls the native methodĪccessFields, which prints out the value of these two JNI functions to access instance member variables and another set of JNI functions to access class member variables.Ĭlass with one class integer member variable si and an instance Similar to accessing methods, you use one set of You can get and set both instance and class member variables. The JNI provides functions that native methods use to get and set Lesson: Interacting with Java from the Native Side Accessing Java Member Variables The Java TM Tutorial ![]()
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