How can I return in a native method a Java type?

Question

Hi,
i want to return in the native methode ja Java type java.awt.Dimension!
How can I do this?
Java code:--------------------------------------------------------------------------------
public native java.awt.Dimension getSize()
generating the JNI header file
JNI header code:--------------------------------------------------------------------------------
JNIEXPORT jobject JNICALL Java_Video_getSize(JNIEnv *, jobject)
my c function looks like this
code:--------------------------------------------------------------------------------
JNIEXPORT jobject JNICALL Java_Video_getSize(JNIEnv *env, jobject obj)
return ???????
how can I return in C an object like jawa.awt.Dimension?
Thx
Ronny

Answer 1

Here is my 2 cents for a way we pass data between Java and C via the Java Native Interface. This excerpt is an example of passing an int value through a locally created Integer wrapper class, which must be adapted for local use. Note that because of the wrapper, return values are not needed.
1. Create the Java class file.
* This class encapsulates a Java <CODE>int</CODE> primitive.
* This class was created to allow programmers to change
* the value of an existing integer object without being
* forced to create a new object (as is the case with the
* Java Integer object).
public class LocalInteger
     private int     value;
     * Creates a LocalInteger object and initializes
     * it to <I>0</I> (the default in Java).
     public LocalInteger ()
          super ();
     * Creates a LocalInteger object and initializes
     * it using the given <I>int</I> value.
     * @param i Integer value to use in initializing
     * the object.
     public LocalInteger (int i)
          super ();
          value = i;
     * Gets the value of the object.
     * @return The value of the object.
     public int getValue ()
          return (value);
2. Create the jni header file.
DLL_EXTERN void jni_GetValue_from_LocalInteger(int* LocalInteger, JNIEnv *env, jobject thisLocalInteger);
3. Create the C file.
/*start of jni header****************************************
*NAME/TITLE:       jni_GetValue_from_LocalInteger
*DESCRIPTION:      This routine copies the integer value
* from the Java LocalInteger object to the
* C 'int' variable.
*CALLING SEQUENCE: jni_GetValue_from_LocalInteger (LocalInteger,
* env,
* thisLocalInteger)
*PARAMETERS:
* Type Name I/O Description
* int * LocalInteger I/O C variable
* JNIEnv * env I JNIEnv pointer
* jobject thisLocalInteger I Java object
*RETURN:           N/A
**end of header*********************************************/
/* ********************** BEGIN CODE ********************** */
DLL_EXPORT
void jni_GetValue_from_LocalInteger(int* LocalInteger, JNIEnv *env, jobject thisLocalInteger)
     LocalInteger = (int) (env)->GetIntField(env, thisLocalInteger, LocalInteger_Value);