java-native-interface

问题 I have the follow scenario to work on. I was given a shared library (libeffect.so) to use in a Android project i am working for a client. I dont have the shared library source code, i have just the .so file with me. The library is pre-compiled to work on android devices. Along with the shared library I have the method signature public static native void doEffect(int param1, IntBuffer intBuffer); So now I have some questiosn on how to make the call to this native method, of source, if this is

问题 Can we use Ble hardware(Bluetooth low energy) direct from Ndk without any java interface. I am new to NDk. So I don't know about jni, or Ndk. I want to control the bluetooth hardware directly from native code , 回答1: NO and YES. NO: There is no BLE API in ndk. YES: You can talk to BT hardware from C code. In AOSP, look under <>/hardware/libhardware/include/hardware/ there are a bunch of headers. bluetooth.h defines the interface for Android's bluetooth module. Bluedroid implements it. You

问题 Can we use Ble hardware(Bluetooth low energy) direct from Ndk without any java interface. I am new to NDk. So I don't know about jni, or Ndk. I want to control the bluetooth hardware directly from native code , 回答1: NO and YES. NO: There is no BLE API in ndk. YES: You can talk to BT hardware from C code. In AOSP, look under <>/hardware/libhardware/include/hardware/ there are a bunch of headers. bluetooth.h defines the interface for Android's bluetooth module. Bluedroid implements it. You

问题 I write a jni function to set the value of two java Integer object in C, just like this: jni_do_something(JNIEnv *env, jobject thiz, jobject p1, jobject p2) { jclass c; jfieldID id; c = env->FindClass("java/lang/Integer"); if (c==NULL) { LOGD("FindClass failed"); return -1; } id = env->GetFieldID(c, "value", "I"); if (id==NULL) { LOGD("GetFiledID failed"); return -1; } env->SetIntField(p1, id, 5); env->SetIntField(p2, id, 10); return 0; } In java, I called this function: native int do

问题 I write a jni function to set the value of two java Integer object in C, just like this: jni_do_something(JNIEnv *env, jobject thiz, jobject p1, jobject p2) { jclass c; jfieldID id; c = env->FindClass("java/lang/Integer"); if (c==NULL) { LOGD("FindClass failed"); return -1; } id = env->GetFieldID(c, "value", "I"); if (id==NULL) { LOGD("GetFiledID failed"); return -1; } env->SetIntField(p1, id, 5); env->SetIntField(p2, id, 10); return 0; } In java, I called this function: native int do

问题 I'm trying to use JNI and getting java.lang.UnsatisfiedLinkError. Unlike the other million questions asked about this, I have the lib on my path, and have even seen the exception change when I remove it. I'm sure that something is wrong with the dll I have created, but I'm not sure what. Here is my java class code: package com; public class Tune { static { System.loadLibrary("lala"); } public static void main(String[] args) { Tune j = new Tune(); System.out.println("2+6="+j.add(2, 6)); }

问题 I need to calculate Math.exp() from java very frequently, is it possible to get a native version to run faster than java 's Math.exp() ?? I tried just jni + C, but it's slower than just plain java . 回答1: +1 to writing your own exp() implementation. That is, if this is really a bottle-neck in your application. If you can deal with a little inaccuracy, there are a number of extremely efficient exponent estimation algorithms out there, some of them dating back centuries. As I understand it, Java

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 3 years ago . I'm working on building an app to scan directly from TWAIN scanner to a Java applet. I'm already aware of Morena and JTwain, but they cost money. I need free. I could re-invent the wheel with JNI, but it seems like someone has probably already done this as a FOSS tool. Is anyone familiar with a free tool that

问题 I am trying to access the raw data of a Bitmap in ARGB_8888 format on Android, using the copyPixelsToBuffer and copyPixelsFromBuffer methods. However, invocation of those calls seems to always apply the alpha channel to the rgb channels. I need the raw data in a byte[] or similar (to pass through JNI; yes, I know about bitmap.h in Android 2.2, cannot use that). Here is a sample: // Create 1x1 Bitmap with alpha channel, 8 bits per channel Bitmap one = Bitmap.createBitmap(1,1,Bitmap.Config.ARGB

问题 I am trying to access the raw data of a Bitmap in ARGB_8888 format on Android, using the copyPixelsToBuffer and copyPixelsFromBuffer methods. However, invocation of those calls seems to always apply the alpha channel to the rgb channels. I need the raw data in a byte[] or similar (to pass through JNI; yes, I know about bitmap.h in Android 2.2, cannot use that). Here is a sample: // Create 1x1 Bitmap with alpha channel, 8 bits per channel Bitmap one = Bitmap.createBitmap(1,1,Bitmap.Config.ARGB