如何将jstring
来自 JNIC
代码的 a 发送到Java
接收 aString
作为参数的函数?
我已经阅读过类似的功能,callVoidMethodA(....)
但它们不接受诸如jstring
.
如何将jstring
来自 JNIC
代码的 a 发送到Java
接收 aString
作为参数的函数?
我已经阅读过类似的功能,callVoidMethodA(....)
但它们不接受诸如jstring
.
您还没有提到目标类名称和目标方法签名。例如,考虑java.lang.StringBuilder.append(java.lang.String)方法。
// First lets assume you have already received the next variables
void foo( JNIEnv* env, jobject obj )
{
// Call StringBuilder.append() method
}
现在您需要类名和方法签名(根据docs)
static char const StringBuilder_ClassName = "java/lang/StringBuilder";
static char const StringBuilder_append_MethodName = "append";
static char const StringBuilder_append_MethodSignature =
"(Ljava/lang/String;)Ljava/lang/StringBuilder;";
要从 JNI 代码调用 java 方法,您应该获取jmethodID
static jclass StringBuilder_Class = 0;
static jmethodID StringBuilder_append_Method = 0;
void Init( JNIEnv* env )
{
if( StringBuilder_Class == 0 ) {
StringBuilder_Class = (*env)->FindClass( env, StringBuilder_ClassName );
// TODO: Handle error if class not found
}
if( StringBuilder_append_Method == 0 ) {
StringBuilder_append_Method = (*env)->GetMethodID( env, StringBuilder_Class,
StringBuilder_append_MethodName, StringBuilder_append_MethodSignature );
// TODO: Handle error if method not found
}
}
void foo( JNIEnv* env, jobject obj )
{
Init();
char* str;
// str = ...;
jstring jString = (*env)->NewStringUTF( env, str );
// Because StringBuild.append() returns object, you should call CallObjectMethod
jobject ret = (*env)->CallObjectMethod( env, obj, jString );
// Here you can release local references, i.e.
// (*env)->DeleteLocalRef( env, ret );
// (*env)->DeleteLocalRef( env, jString );
// But it is not necessary. Local references are released automatically when
// thread returns from JNI code to Java code.
// So you can ignore the returned value and not to release the jString local
// reference, i.e. just call
// (*env)->CallObjectMethod( env, obj, jString );
}
JNIEXPORT jstring JNICALL
Java_Prompt_getLine(JNIEnv *env, jobject obj)
{
char *buf = "Hi !!!!";
jstring jString = (*env)->NewStringUTF(env, buf);
free(buf);
return jString;
}