java-native-interface

问题 As we known, JNI is a bridge between Java and C++. Recently i'm coding for a Java project and it's main module is based on C++ which need to store a large number of GlobalReference . And it will increase along with activity being opened. Therefore the maximum number (65535) of GlobalReferences become a serious problem and i have to solve the problem using peculiar method. So i'm interested in why there is a limit on GlobalReferences . Is it only for detecting the memory leaks as other's

问题 I have a Java program that needs to load a native code library (through JNI with SWIG) but when I tried to run it I got an error as follows: Exception in thread "main" java.lang.UnsatisfiedLinkError: /usr/local/lib/libmyapp_jni.so.0.0.0: /usr/local/lib/libmyapp_jni.so.0.0.0: undefined symbol: __cxa_pure_virtual at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary1(ClassLoader.java:1939) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1864) at

问题 Goal: Link Java to Swift Problem: I get an UnsatisfiedLinkError when trying to load a JNI .dylib file that is linked with a Swift .dylib file when calling System#loadLibrary(String). Expected Behavior: The dependency of the Java .dylib would be automatically loaded or the call to System.loadLibrary("SwiftCode") would load the dependency (the only solution I could come up with). Note: I am combining this github tutorial and this Medium article to create my JNI .dylib file and this tutorial to

问题 Id like to make a simple function, that return value of two Strings. basically: java public native String getAppendedString(String name); c jstring Java_com_example_hellojni_HelloJni_getAppendedString(JNIEnv* env, jobject thiz, jstring s) { jstring sx = (*env)->GetStringUTFChars(env, s, NULL); return ((*env)->NewStringUTF(env, "asd ")+sx); } its say jni/hello-jni.c:32: warning: initialization discards qualifiers from pointer target type jni/hello-jni.c:34: error: invalid operands to binary +

问题 Id like to make a simple function, that return value of two Strings. basically: java public native String getAppendedString(String name); c jstring Java_com_example_hellojni_HelloJni_getAppendedString(JNIEnv* env, jobject thiz, jstring s) { jstring sx = (*env)->GetStringUTFChars(env, s, NULL); return ((*env)->NewStringUTF(env, "asd ")+sx); } its say jni/hello-jni.c:32: warning: initialization discards qualifiers from pointer target type jni/hello-jni.c:34: error: invalid operands to binary +

问题 it is very important to me to write to a file with the O_DIRECT flag. This is how I open the file: //Open the file int fd; if((fd = open(inFilepath, O_WRONLY | O_CREAT |O_SYNC |O_DIRECT,S_IRUSR|S_IWUSR))<0) { //Error handling return; } I know about O_DIRECT's alignment restrictions. This is why I initialize my buffer with calloc: char *buff = (char *) calloc((size_t) 1,sizeof(char)); if(write(fd,buff,(size_t)1)<1) { //Error logging free(buff); return -1; } And I get the write: Invalid

问题 it is very important to me to write to a file with the O_DIRECT flag. This is how I open the file: //Open the file int fd; if((fd = open(inFilepath, O_WRONLY | O_CREAT |O_SYNC |O_DIRECT,S_IRUSR|S_IWUSR))<0) { //Error handling return; } I know about O_DIRECT's alignment restrictions. This is why I initialize my buffer with calloc: char *buff = (char *) calloc((size_t) 1,sizeof(char)); if(write(fd,buff,(size_t)1)<1) { //Error logging free(buff); return -1; } And I get the write: Invalid

问题 I am trying to interface with an MSI SDR dongle, using an android app This device is a clone of the SDRPlay SDR device, and is compatible with it's software and drivers I am trying to interface with this using an OTG cable and android phone The android drivers for this can be downloaded from here https://www.sdrplay.com/downloads/ It is in the Android tab under the API/HW – V2.11 (15TH NOV 2017) link (https://www.sdrplay.com/anddl.php) A possible sample code for this driver can be found here:

问题 I have coded a library that provides some function add, sub, divide, multi by c/c++ programming language. It's built to library.so by using Android NDK. So now, I want to call these function of library by using Android. I want to as How I can do ? Thank. 回答1: NDK Package Android Studio only includes the default tools and SDK, so download and install the NDK package separately. There are two ways to do this. The first and easiest is the automatic installation option in the SDK Tools tab. This

问题 I am updating my projects to use Android ndk 16b and it was previously using 12b (was working fine). After I updated, I am running into the following error while building the final .so: /Users/ssk/code/client/git/thirdparty/android-ndk-r16b/android-ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: error: jni/../../../shared-library/SharedCommon/build/arm-linux-androideabi/lib/libSharedCommon.a: no