JNI文件添加

JNI文件夹中一般包括Android.mk、native.cpp和其他.c/.h文件

Android.mk文件

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)#LOCAL_MODULE_TAGS := eng samplesLOCAL_MODULE_TAGS := optional# This is the target being built.LOCAL_MODULE:= libamtjni #这里是JNI库名，lib+名字+jni# All of the source files that we will compile.LOCAL_SRC_FILES:= \   #所要编译的源码 .c和.cpp文件  native.cpp \  amt_command.c# All of the shared libraries we link against.LOCAL_SHARED_LIBRARIES := \  #需要连接的共享库libutils# No static libraries.LOCAL_STATIC_LIBRARIES :=# Also need the JNI headers.LOCAL_C_INCLUDES += \$(JNI_H_INCLUDE)# No special compiler flags.LOCAL_CFLAGS +=# Don't prelink this library.  For more efficient code, you may want# to add this library to the prelink map and set this to true. However,# it's difficult to do this for applications that are not supplied as# part of a system image.LOCAL_PRELINK_MODULE := falseinclude $(BUILD_SHARED_LIBRARY)

native.cpp文件

#include <utils/Log.h>#include <stdio.h>#include "jni.h"#include <stdlib.h>#define LOGD  ALOGD#define LOGE  ALOGE#define LOGI  ALOGIstatic jstring                           app_test(JNIEnv *env, jobject thiz)     {             FILE *fp = NULL;                                    char serial_no_buffer_a[100 + 1];                  char *usb_serial_no_file_path = "/amt/usb_serial";         memset( serial_no_buffer_a, 0, sizeof(serial_no_buffer_a) );  fp = fopen(usb_serial_no_file_path, "r");   if(NULL != fp)   {  //if( EOF != fscanf(fp, "%s", serial_no_buffer_a))   fread( serial_no_buffer_a, sizeof(serial_no_buffer_a) - 1,  1,  fp );   if( feof(fp) )     {       LOGI( "Settings status read adb serial no ok and content is %s", serial_no_buffer_a  );               }       else      {       LOGI("Settings status read fread error or file content length bigger then 100" );       }        fclose(fp);    }    else    {    LOGI("Settings status read fopen error or usb serial file not exist" );    LOGI("Settings status return default serial no T802");    strcpy( serial_no_buffer_a, "T802" );   }        return env->NewStringUTF( serial_no_buffer_a );}                                                                                                                             static const char *classPathName = "com/android/settings/deviceinfo/Native";                                                       static JNINativeMethod methods[] = {    {"uni_serial_no_read", "()Ljava/lang/String;", (void*)uni_serial_no_read },             {"java文件中调用的函数名","(JNI函数参数类型)JNI函数返回值类型",(void*)jni函数名}};   /* * Register several native methods for one class. */static int registerNativeMethods(JNIEnv* env, const char* className,    JNINativeMethod* gMethods, int numMethods){    jclass clazz;        clazz = env->FindClass(className);    if (clazz == NULL) {        LOGE("Native registration unable to find class '%s'", className);        return JNI_FALSE;    }    if (env->RegisterNatives(clazz, gMethods, numMethods) < 0) {        LOGE("RegisterNatives failed for '%s'", className);        return JNI_FALSE;    }       return JNI_TRUE;}/* * Register native methods for all classes we know about. * * returns JNI_TRUE on success. */static int registerNatives(JNIEnv* env){  if (!registerNativeMethods(env, classPathName,                 methods, sizeof(methods) / sizeof(methods[0]))) {    return JNI_FALSE;  }return JNI_TRUE;}/* * This is called by the VM when the shared library is first loaded. */ typedef union {    JNIEnv* env;    void* venv;} UnionJNIEnvToVoid;         jint JNI_OnLoad(JavaVM* vm, void* reserved){    UnionJNIEnvToVoid uenv;    uenv.venv = NULL;    jint result = -1;    JNIEnv* env = NULL;        LOGI("JNI_OnLoad");           if (vm->GetEnv(&uenv.venv, JNI_VERSION_1_4) != JNI_OK) {        LOGE("ERROR: GetEnv failed");        goto bail;    }    env = uenv.env;           if (registerNatives(env) != JNI_TRUE) {        LOGE("ERROR: registerNatives failed");        goto bail;    }        result = JNI_VERSION_1_4;    bail:    return result;}

 

在java文件中，如果调用JNI的地方比较少，可以直接在调用的文件中加入

class Native {     static {           System.loadLibrary("编译的jni库名-lib");#如：编译的出来的名字叫 libtestjni ，此处名字为testjni    }

 static native JNI库中java的函数名；

}

如果需要很多文件调用或JNI文件中函数比较多，可以在java文件中新创建一个Native.java

package 包名;public class Native {    static {        // The runtime will add "lib" on the front and ".o" on the end of        // the name supplied to loadLibrary.        System.loadLibrary("amtjni");    }    static native int add(int a, int b);       static native 返回值类型 函数名（参数）；#此处的函数名要和Native.cpp中的JNINativeMethod methods[]第一列函数名一致；    }

在其他java文件中就可以直接以Native.函数名 来调用