android利用JNI调用C++自定义类

找了好久关于android调用C/C++库的文章，但是始终没有一片是关于android利用jni调用C++自定义类的文章，无奈只好看android的源代码，学习android的图形库的实现，因为它的实现底层也是利用C++的skia库。下面就3个文件来描述。

首先是你在java中的一个类，用于你在应用程序中调用这里取名叫Person类

package whf.jnitest;public class Person {static{System.loadLibrary("Person");}private int mNativePerson;public Person(){mNativePerson = init();}protected void finalize(){try {            finalizer(mNativePerson);        } finally {            try {super.finalize();} catch (Throwable e) {// TODO Auto-generated catch blocke.printStackTrace();}        }}public int getAge(){return native_getAge(mNativePerson);}public void setAge(int age){native_setAge(mNativePerson, age);}private native void finalizer(int nPerson);public native intadd(int a, int b);publicnative int  sub(int a, int b);private native int  init();private native intnative_getAge(int nPerson);private native void native_setAge(int nPerson, int age);}

然后你的C++文件就如下，我定义为CPerson类

#define LOG_TAG "this is a first JNI test"#include #include #include #include #include #include #include #include "jni.h"#include "CPerson.h"jint add(JNIEnv *env, jobject obj, jint a, jint b){return a + b;}    jint Java_whf_jnitest_Person_sub(JNIEnv *env, jobject obj, jint a, jint b){return a - b;}void Java_whf_jnitest_Person_finalizer(JNIEnv *env, jobject clazz, CPerson *obj){delete obj;}CPerson * Java_whf_jnitest_Person_init(JNIEnv *env, jobject clazz){    CPerson *p = new CPerson();return p;}void Java_whf_jnitest_Person_setAge(JNIEnv *env, jobject clazz, CPerson *obj, jint age){return obj->setAge(age);}jint Java_whf_jnitest_Person_getAge(JNIEnv *env, jobject clazz, CPerson *obj){return obj->getAge();}static JNINativeMethod methods[]{{"add", "(II)I", (void *)add},{"sub", "(II)I", (void *)Java_whf_jnitest_Person_sub},{"finalizer", "(I)V", (void *)Java_whf_jnitest_Person_finalizer},{"init", "()I", (void *)Java_whf_jnitest_Person_init},{"native_setAge", "(II)V", (void *)Java_whf_jnitest_Person_setAge},{"native_getAge", "(I)I", (void *)Java_whf_jnitest_Person_getAge},};static const char * classPathName = "whf/jnitest/Person";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;}static int registerNatives(JNIEnv* env){  if (!registerNativeMethods(env, classPathName, methods, sizeof(methods) / sizeof(methods[0]))) {return JNI_FALSE;  }  return JNI_TRUE;}typedef union {JNIEnv* env;void* venv;} UnionJNIEnvToVoid;/* This function will be call when the library first be loaded */jint JNI_OnLoad(JavaVM* vm, void* reserved){UnionJNIEnvToVoid uenv;JNIEnv* env = NULL;//LOGI("JNI_OnLoad!");if (vm->GetEnv((void**)&uenv.venv, JNI_VERSION_1_4) != JNI_OK) {//LOGE("ERROR: GetEnv failed");return -1;}env = uenv.env;;        //jniRegisterNativeMethods(env, "whf/jnitest/Person", methods, sizeof(methods) / sizeof(methods[0]));if (registerNatives(env) != JNI_TRUE) {//LOGE("ERROR: registerNatives failed");return -1;} return JNI_VERSION_1_4;}

CPerson的声明如下：

#ifndef _CPERSON_H_#define _CPERSON_H_class CPerson{private:    int m_age;public:    CPerson();    int getAge();    void setAge(int age);};#endif

这样一个简单的JNI调用C++自定义类就实现了

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