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JNI 回调小记

2024-07-11 13:14:29   224人阅读

javah在eclipse中设置参数：location(javah.exe的位置)working dir(${project_loc}/src)

-classpath .;./classes -d ${project_loc}\jni -jni ${java_type_name}

回调的java代码

public class HelloWorld {    static {        System.loadLibrary("jnidemo");    }    public void myCallbackFunc(String nMsg) {        Log.v("EagleTag", "back message:" + nMsg);    }    private void throwException() throws NullPointerException {        throw new NullPointerException("Null pointer");    }    public native String DisplayHello(String inputStr);}

C代码

jstring JNICALL Java_com_example_jnidemo_HelloWorld_DisplayHello(JNIEnv *env,        jobject obj, jstring what) {    const jbyte *l_what;    char *result;    l_what = (*env)->GetStringUTFChars(env, what, NULL);    if (l_what == NULL) {        return NULL; /* OutOfMemoryError already thrown */    }    result = malloc(strlen(l_what) + 6);    if (result == NULL) {        return NULL;    }    sprintf(result, "中文reiver %s", l_what);    //回调    char tChar[256];    gJniClass = 0;    gJinMethod = 0;    gJniClass = (*env)->GetObjectClass(env, obj);    if (gJniClass == 0 || gJniClass == NULL)        return (*env)->NewStringUTF(env, "-1");    gJinMethod = (*env)->GetMethodID(env, gJniClass, "myCallbackFunc",            "(Ljava/lang/String;)V");    if (gJinMethod == 0 || gJinMethod == NULL)        return (*env)->NewStringUTF(env, "-2");    strcpy(tChar, result);    (*env)->CallVoidMethod(env, obj, gJinMethod,            (*env)->NewStringUTF(env, tChar));    return (*env)->NewStringUTF(env, result);}

 


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