Android jni头文件详解
jni头文件的源码虽然有1144行，但是归纳起来可以分为一下几类：
- jni层的数据类型的定义；
- JNINativeMethod结构体的定义；
- JNINativeInterface结构体的定义；
- JNIInvokeInterface结构体的定义
- _JNIEnv结构体的定义；
- _JavaVM结构体的定义；
- JavaVMAttachArgs结构体的定义
- JavaVMOption结构体的定义
- JavaVMInitArgs结构体的定义
- JNI_OnLoad方法的定义；
- JNI_OnUnload方法的定义
一、 jni层的数据类型的定义
1、与java语言对应的基础数据类型定义
/* Primitive types that match up with Java equivalents. */
typedef uint8_t jboolean; /* unsigned 8 bits */
typedef int8_t jbyte; /* signed 8 bits */
typedef uint16_t jchar; /* unsigned 16 bits */
typedef int16_t jshort; /* signed 16 bits */
typedef int32_t jint; /* signed 32 bits */
typedef int64_t jlong; /* signed 64 bits */
typedef float jfloat; /* 32-bit IEEE 754 */
typedef double jdouble; /* 64-bit IEEE 754 */
2、c++里面的引用数据类型定义
class _jobject {};
class _jclass : public _jobject {};
class _jstring : public _jobject {};
class _jarray : public _jobject {};
class _jobjectArray : public _jarray {};
class _jbooleanArray : public _jarray {};
class _jbyteArray : public _jarray {};
class _jcharArray : public _jarray {};
class _jshortArray : public _jarray {};
class _jintArray : public _jarray {};
class _jlongArray : public _jarray {};
class _jfloatArray : public _jarray {};
class _jdoubleArray : public _jarray {};
class _jthrowable : public _jobject {};
typedef _jobject* jobject;
typedef _jclass* jclass;
typedef _jstring* jstring;
typedef _jarray* jarray;
typedef _jobjectArray* jobjectArray;
typedef _jbooleanArray* jbooleanArray;
typedef _jbyteArray* jbyteArray;
typedef _jcharArray* jcharArray;
typedef _jshortArray* jshortArray;
typedef _jintArray* jintArray;
typedef _jlongArray* jlongArray;
typedef _jfloatArray* jfloatArray;
typedef _jdoubleArray* jdoubleArray;
typedef _jthrowable* jthrowable;
typedef _jobject* jweak;
二、JNINativeMethod结构体的定义
typedef struct {
const char* name;
const char* signature;
void* fnPtr;
} JNINativeMethod;
name:java层native方法的方法名
signature：java层native方法的参数类型和返回值的类型（详细讲解）
fnPtr：cpp文件定义的方法名
三、JNINativeInterface结构体的定义
struct JNINativeInterface {
void* reserved0;
void* reserved1;
void* reserved2;
void* reserved3;
//获取版本号
jint (*GetVersion)(JNIEnv *);
//定义一个类
jclass (*DefineClass)(JNIEnv*, const char*, jobject, const jbyte*,
jsize);
//查找类，通常用来查找java层的类
jclass (*FindClass)(JNIEnv*, const char*);
//将一个Method对象转换为方法ID
jmethodID (*FromReflectedMethod)(JNIEnv*, jobject);
//将一个Field对象转换为属性ID
jfieldID (*FromReflectedField)(JNIEnv*, jobject);
/* spec doesn't show jboolean parameter */
//反射得到Method对象
jobject (*ToReflectedMethod)(JNIEnv*, jclass, jmethodID, jboolean);
//获取jclass的父类
jclass (*GetSuperclass)(JNIEnv*, jclass);
//判断第一个jclass的对象是否可以安全地转化为第二个jclass的对象
jboolean (*IsAssignableFrom)(JNIEnv*, jclass, jclass);
/* spec doesn't show jboolean parameter */
//反射获取属性的对象
jobject (*ToReflectedField)(JNIEnv*, jclass, jfieldID, jboolean);
//根据obj构造java.lang.Throwable对象并抛出异常
jint (*Throw)(JNIEnv*, jthrowable);
//根据异常类clazz和对应的message信息构造新的异常对象并抛出异常
jint (*ThrowNew)(JNIEnv *, jclass, const char *);
//判断是否有异常发生，异常保持待throw的状态直到Native层调用ExceptionClear或者Java层处理了异常。
jthrowable (*ExceptionOccurred)(JNIEnv*);
//通过系统错误日志譬如stderr打印异常的堆栈信息。
void (*ExceptionDescribe)(JNIEnv*);
//清理任何待抛出的异常。如果当前没有任何待抛异常，那函数不产生任何作用
void (*ExceptionClear)(JNIEnv*);
//致命异常，用于输出一个异常信息，并终止当前JVM实例（即退出程序）
void (*FatalError)(JNIEnv*, const char*);
//创建一个新的局部引入帧，至少一个给定的局部引用可以被创建的数
jint (*PushLocalFrame)(JNIEnv*, jint);
//弹出局部帧
jobject (*PopLocalFrame)(JNIEnv*, jobject);
//创建新的全局引用
jobject (*NewGlobalRef)(JNIEnv*, jobject);
//删除全局引用
void (*DeleteGlobalRef)(JNIEnv*, jobject);
//删除局部引用
void (*DeleteLocalRef)(JNIEnv*, jobject);
//是否为相同对象
jboolean (*IsSameObject)(JNIEnv*, jobject, jobject);
//创建局部引用
jobject (*NewLocalRef)(JNIEnv*, jobject);
//在当前线程确保至少一个可以被创建的给定局部引用数。
jint (*EnsureLocalCapacity)(JNIEnv*, jint);
//分配新 Java 对象而不调用该对象的任何构造函数。返回该对象的引用。
jobject (*AllocObject)(JNIEnv*, jclass);
//构造新的 Java 对象。方法 ID指示应调用的构造函数方法。该 ID 必须通过调用 GetMethodID() 获得，且调用时的方法名必须为 ，而返回类型必须为 void (V)
jobject (*NewObject)(JNIEnv*, jclass, jmethodID, ...);
//在methodID 后面，放了一个类型为 va_lis t的 args，参数存放着所有需要传递给构造函数的参数。NewObjectv() 接收到所有的参数，并且按照顺序将它们传递给需要调用的 Java 方法。
jobject (*NewObjectV)(JNIEnv*, jclass, jmethodID, va_list);
//在methodID 后面，放了一个类型为 jvalue 的参数数组——args，该数组存放着所有需要传递给构造函数的参数。NewObjectA() 接收到这个数组中的所有参数，并且按照顺序将它们传递给需要调用的 Java 方法
jobject (*NewObjectA)(JNIEnv*, jclass, jmethodID, const jvalue*);
//获取对象的“类”
jclass (*GetObjectClass)(JNIEnv*, jobject);
//这个对象是否是这个特定类或者是它的子类的一个实例
jboolean (*IsInstanceOf)(JNIEnv*, jobject, jclass);
//获取方法ID
jmethodID (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);
//CallMethod 调用返回类型为Type的函数
jobject (*CallObjectMethod)(JNIEnv*, jobject, jmethodID, ...);
jobject (*CallObjectMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jobject (*CallObjectMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jboolean (*CallBooleanMethod)(JNIEnv*, jobject, jmethodID, ...);
jboolean (*CallBooleanMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jboolean (*CallBooleanMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jbyte (*CallByteMethod)(JNIEnv*, jobject, jmethodID, ...);
jbyte (*CallByteMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jbyte (*CallByteMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jchar (*CallCharMethod)(JNIEnv*, jobject, jmethodID, ...);
jchar (*CallCharMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jchar (*CallCharMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jshort (*CallShortMethod)(JNIEnv*, jobject, jmethodID, ...);
jshort (*CallShortMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jshort (*CallShortMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jint (*CallIntMethod)(JNIEnv*, jobject, jmethodID, ...);
jint (*CallIntMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jint (*CallIntMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jlong (*CallLongMethod)(JNIEnv*, jobject, jmethodID, ...);
jlong (*CallLongMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jlong (*CallLongMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jfloat (*CallFloatMethod)(JNIEnv*, jobject, jmethodID, ...);
jfloat (*CallFloatMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jfloat (*CallFloatMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
jdouble (*CallDoubleMethod)(JNIEnv*, jobject, jmethodID, ...);
jdouble (*CallDoubleMethodV)(JNIEnv*, jobject, jmethodID, va_list);
jdouble (*CallDoubleMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
void (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);
void (*CallVoidMethodV)(JNIEnv*, jobject, jmethodID, va_list);
void (*CallVoidMethodA)(JNIEnv*, jobject, jmethodID, const jvalue*);
//CallNonvirtualMethod系列例程和CallMethod系列例程是不同的。CallMethod例程根据对象的类调用方法，而CallNonvirtualMethod例程根据jclass参数指定的类调用方法，从该类中获得方法ID。方法ID必须从对象的实际类或其超类之一获得
jobject (*CallNonvirtualObjectMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jobject (*CallNonvirtualObjectMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jobject (*CallNonvirtualObjectMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jboolean (*CallNonvirtualBooleanMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jboolean (*CallNonvirtualBooleanMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jboolean (*CallNonvirtualBooleanMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jbyte (*CallNonvirtualByteMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jbyte (*CallNonvirtualByteMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jbyte (*CallNonvirtualByteMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jchar (*CallNonvirtualCharMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jchar (*CallNonvirtualCharMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jchar (*CallNonvirtualCharMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jshort (*CallNonvirtualShortMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jshort (*CallNonvirtualShortMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jshort (*CallNonvirtualShortMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jint (*CallNonvirtualIntMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jint (*CallNonvirtualIntMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jint (*CallNonvirtualIntMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jlong (*CallNonvirtualLongMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jlong (*CallNonvirtualLongMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jlong (*CallNonvirtualLongMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jfloat (*CallNonvirtualFloatMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jfloat (*CallNonvirtualFloatMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jfloat (*CallNonvirtualFloatMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
jdouble (*CallNonvirtualDoubleMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
jdouble (*CallNonvirtualDoubleMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
jdouble (*CallNonvirtualDoubleMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
void (*CallNonvirtualVoidMethod)(JNIEnv*, jobject, jclass,
jmethodID, ...);
void (*CallNonvirtualVoidMethodV)(JNIEnv*, jobject, jclass,
jmethodID, va_list);
void (*CallNonvirtualVoidMethodA)(JNIEnv*, jobject, jclass,
jmethodID, const jvalue*);
//返回类的实例（非静态）字段的字段ID。该字段由其名称和签名指定
jfieldID (*GetFieldID)(JNIEnv*, jclass, const char*, const char*);
//GetField 获取类型为Type的属性
jobject (*GetObjectField)(JNIEnv*, jobject, jfieldID);
jboolean (*GetBooleanField)(JNIEnv*, jobject, jfieldID);
jbyte (*GetByteField)(JNIEnv*, jobject, jfieldID);
jchar (*GetCharField)(JNIEnv*, jobject, jfieldID);
jshort (*GetShortField)(JNIEnv*, jobject, jfieldID);
jint (*GetIntField)(JNIEnv*, jobject, jfieldID);
jlong (*GetLongField)(JNIEnv*, jobject, jfieldID);
jfloat (*GetFloatField)(JNIEnv*, jobject, jfieldID);
jdouble (*GetDoubleField)(JNIEnv*, jobject, jfieldID);
//SetField 设置类型为Type的属性值
void (*SetObjectField)(JNIEnv*, jobject, jfieldID, jobject);
void (*SetBooleanField)(JNIEnv*, jobject, jfieldID, jboolean);
void (*SetByteField)(JNIEnv*, jobject, jfieldID, jbyte);
void (*SetCharField)(JNIEnv*, jobject, jfieldID, jchar);
void (*SetShortField)(JNIEnv*, jobject, jfieldID, jshort);
void (*SetIntField)(JNIEnv*, jobject, jfieldID, jint);
void (*SetLongField)(JNIEnv*, jobject, jfieldID, jlong);
void (*SetFloatField)(JNIEnv*, jobject, jfieldID, jfloat);
void (*SetDoubleField)(JNIEnv*, jobject, jfieldID, jdouble);
//获取类的实例静态方法的ID
jmethodID (*GetStaticMethodID)(JNIEnv*, jclass, const char*, const char*);
//CallStaticMethod 调用静态的类型为Type的方法
jobject (*CallStaticObjectMethod)(JNIEnv*, jclass, jmethodID, ...);
jobject (*CallStaticObjectMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jobject (*CallStaticObjectMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jboolean (*CallStaticBooleanMethod)(JNIEnv*, jclass, jmethodID, ...);
jboolean (*CallStaticBooleanMethodV)(JNIEnv*, jclass, jmethodID,va_list);
jboolean (*CallStaticBooleanMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jbyte (*CallStaticByteMethod)(JNIEnv*, jclass, jmethodID, ...);
jbyte (*CallStaticByteMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jbyte (*CallStaticByteMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jchar (*CallStaticCharMethod)(JNIEnv*, jclass, jmethodID, ...);
jchar (*CallStaticCharMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jchar (*CallStaticCharMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jshort (*CallStaticShortMethod)(JNIEnv*, jclass, jmethodID, ...);
jshort (*CallStaticShortMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jshort (*CallStaticShortMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jint (*CallStaticIntMethod)(JNIEnv*, jclass, jmethodID, ...);
jint (*CallStaticIntMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jint (*CallStaticIntMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jlong (*CallStaticLongMethod)(JNIEnv*, jclass, jmethodID, ...);
jlong (*CallStaticLongMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jlong (*CallStaticLongMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jfloat (*CallStaticFloatMethod)(JNIEnv*, jclass, jmethodID, ...);
jfloat (*CallStaticFloatMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jfloat (*CallStaticFloatMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
jdouble (*CallStaticDoubleMethod)(JNIEnv*, jclass, jmethodID, ...);
jdouble (*CallStaticDoubleMethodV)(JNIEnv*, jclass, jmethodID, va_list);
jdouble (*CallStaticDoubleMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
void (*CallStaticVoidMethod)(JNIEnv*, jclass, jmethodID, ...);
void (*CallStaticVoidMethodV)(JNIEnv*, jclass, jmethodID, va_list);
void (*CallStaticVoidMethodA)(JNIEnv*, jclass, jmethodID, const jvalue*);
//获取静态属性ID
jfieldID (*GetStaticFieldID)(JNIEnv*, jclass, const char*,
const char*);
//GetStaticField 获取静态的类型为Type的属性
jobject (*GetStaticObjectField)(JNIEnv*, jclass, jfieldID);
jboolean (*GetStaticBooleanField)(JNIEnv*, jclass, jfieldID);
jbyte (*GetStaticByteField)(JNIEnv*, jclass, jfieldID);
jchar (*GetStaticCharField)(JNIEnv*, jclass, jfieldID);
jshort (*GetStaticShortField)(JNIEnv*, jclass, jfieldID);
jint (*GetStaticIntField)(JNIEnv*, jclass, jfieldID);
jlong (*GetStaticLongField)(JNIEnv*, jclass, jfieldID);
jfloat (*GetStaticFloatField)(JNIEnv*, jclass, jfieldID);
jdouble (*GetStaticDoubleField)(JNIEnv*, jclass, jfieldID);
//SetStaticField 设置静态的类型为Type的属性值
void (*SetStaticObjectField)(JNIEnv*, jclass, jfieldID, jobject);
void (*SetStaticBooleanField)(JNIEnv*, jclass, jfieldID, jboolean);
void (*SetStaticByteField)(JNIEnv*, jclass, jfieldID, jbyte);
void (*SetStaticCharField)(JNIEnv*, jclass, jfieldID, jchar);
void (*SetStaticShortField)(JNIEnv*, jclass, jfieldID, jshort);
void (*SetStaticIntField)(JNIEnv*, jclass, jfieldID, jint);
void (*SetStaticLongField)(JNIEnv*, jclass, jfieldID, jlong);
void (*SetStaticFloatField)(JNIEnv*, jclass, jfieldID, jfloat);
void (*SetStaticDoubleField)(JNIEnv*, jclass, jfieldID, jdouble);
//创建新的字符串
jstring (*NewString)(JNIEnv*, const jchar*, jsize);
//获取字符串的长度
jsize (*GetStringLength)(JNIEnv*, jstring);
//获取字符串的指针
const jchar* (*GetStringChars)(JNIEnv*, jstring, jboolean*);
//释放字符串
void (*ReleaseStringChars)(JNIEnv*, jstring, const jchar*);
//创建一个UTF-8的字符串
jstring (*NewStringUTF)(JNIEnv*, const char*);
//获取一个UTF-8的字符串的长度
jsize (*GetStringUTFLength)(JNIEnv*, jstring);
/* JNI spec says this returns const jbyte*, but that's inconsistent */
//获取StringUTFChars的指针
const char* (*GetStringUTFChars)(JNIEnv*, jstring, jboolean*);
//释放UTFChars
void (*ReleaseStringUTFChars)(JNIEnv*, jstring, const char*);
//获取数组的长度
jsize (*GetArrayLength)(JNIEnv*, jarray);
//创建类型为Object的数组
jobjectArray (*NewObjectArray)(JNIEnv*, jsize, jclass, jobject);
//获取类型为Object数组的元素
jobject (*GetObjectArrayElement)(JNIEnv*, jobjectArray, jsize);
//设置类型为Object的数组的元素
void (*SetObjectArrayElement)(JNIEnv*, jobjectArray, jsize, jobject);
//NewArray 创建类型为Type的数组
jbooleanArray (*NewBooleanArray)(JNIEnv*, jsize);
jbyteArray (*NewByteArray)(JNIEnv*, jsize);
jcharArray (*NewCharArray)(JNIEnv*, jsize);
jshortArray (*NewShortArray)(JNIEnv*, jsize);
jintArray (*NewIntArray)(JNIEnv*, jsize);
jlongArray (*NewLongArray)(JNIEnv*, jsize);
jfloatArray (*NewFloatArray)(JNIEnv*, jsize);
jdoubleArray (*NewDoubleArray)(JNIEnv*, jsize);
//GetArrayElements 获取类型为Type数组元素
jboolean* (*GetBooleanArrayElements)(JNIEnv*, jbooleanArray, jboolean*);
jbyte* (*GetByteArrayElements)(JNIEnv*, jbyteArray, jboolean*);
jchar* (*GetCharArrayElements)(JNIEnv*, jcharArray, jboolean*);
jshort* (*GetShortArrayElements)(JNIEnv*, jshortArray, jboolean*);
jint* (*GetIntArrayElements)(JNIEnv*, jintArray, jboolean*);
jlong* (*GetLongArrayElements)(JNIEnv*, jlongArray, jboolean*);
jfloat* (*GetFloatArrayElements)(JNIEnv*, jfloatArray, jboolean*);
jdouble* (*GetDoubleArrayElements)(JNIEnv*, jdoubleArray, jboolean*);
//ReleaseArrayElements 释放类型为Type的数组元素
void (*ReleaseBooleanArrayElements)(JNIEnv*, jbooleanArray,
jboolean*, jint);
void (*ReleaseByteArrayElements)(JNIEnv*, jbyteArray,
jbyte*, jint);
void (*ReleaseCharArrayElements)(JNIEnv*, jcharArray,
jchar*, jint);
void (*ReleaseShortArrayElements)(JNIEnv*, jshortArray,
jshort*, jint);
void (*ReleaseIntArrayElements)(JNIEnv*, jintArray,
jint*, jint);
void (*ReleaseLongArrayElements)(JNIEnv*, jlongArray,
jlong*, jint);
void (*ReleaseFloatArrayElements)(JNIEnv*, jfloatArray,
jfloat*, jint);
void (*ReleaseDoubleArrayElements)(JNIEnv*, jdoubleArray,
jdouble*, jint);
//GetArrayRegion 获取起始下标为jsize，长度为jsize的类型为Type的数组
void (*GetBooleanArrayRegion)(JNIEnv*, jbooleanArray,
jsize, jsize, jboolean*);
void (*GetByteArrayRegion)(JNIEnv*, jbyteArray,
jsize, jsize, jbyte*);
void (*GetCharArrayRegion)(JNIEnv*, jcharArray,
jsize, jsize, jchar*);
void (*GetShortArrayRegion)(JNIEnv*, jshortArray,
jsize, jsize, jshort*);
void (*GetIntArrayRegion)(JNIEnv*, jintArray,
jsize, jsize, jint*);
void (*GetLongArrayRegion)(JNIEnv*, jlongArray,
jsize, jsize, jlong*);
void (*GetFloatArrayRegion)(JNIEnv*, jfloatArray,
jsize, jsize, jfloat*);
void (*GetDoubleArrayRegion)(JNIEnv*, jdoubleArray,
jsize, jsize, jdouble*);
/* spec shows these without const; some jni.h do, some don't */
//SetArrayRegion 设置起始下标为jsize，长度为jsize的类型为Type的数组
void (*SetBooleanArrayRegion)(JNIEnv*, jbooleanArray,
jsize, jsize, const jboolean*);
void (*SetByteArrayRegion)(JNIEnv*, jbyteArray,
jsize, jsize, const jbyte*);
void (*SetCharArrayRegion)(JNIEnv*, jcharArray,
jsize, jsize, const jchar*);
void (*SetShortArrayRegion)(JNIEnv*, jshortArray,
jsize, jsize, const jshort*);
void (*SetIntArrayRegion)(JNIEnv*, jintArray,
jsize, jsize, const jint*);
void (*SetLongArrayRegion)(JNIEnv*, jlongArray,
jsize, jsize, const jlong*);
void (*SetFloatArrayRegion)(JNIEnv*, jfloatArray,
jsize, jsize, const jfloat*);
void (*SetDoubleArrayRegion)(JNIEnv*, jdoubleArray,
jsize, jsize, const jdouble*);
//注册本地方法
jint (*RegisterNatives)(JNIEnv*, jclass, const JNINativeMethod*,jint);
//取消注册类的本地方法
jint (*UnregisterNatives)(JNIEnv*, jclass);
//进入与obj引用的底层Java对象相关联的监视器
jint (*MonitorEnter)(JNIEnv*, jobject);
//退出与obj引用的底层Java对象相关联的监视器
jint (*MonitorExit)(JNIEnv*, jobject);
//返回与当前线程关联的Java VM接口
jint (*GetJavaVM)(JNIEnv*, JavaVM**);
//将偏移量jsize开头处的len个Unicode字符数复制到给定的缓冲区jchar*
void (*GetStringRegion)(JNIEnv*, jstring, jsize, jsize, jchar*);
//将从偏移量开始的Unicode字符的len数转换为经过修改的UTF-8编码，并将结果放在给定的缓冲区char* buf中
void (*GetStringUTFRegion)(JNIEnv*, jstring, jsize, jsize, char*);
//获取基本类型数组的中数组
void* (*GetPrimitiveArrayCritical)(JNIEnv*, jarray, jboolean*);
//释放基本类型数组的中数组
void (*ReleasePrimitiveArrayCritical)(JNIEnv*, jarray, void*, jint);
//
const jchar* (*GetStringCritical)(JNIEnv*, jstring, jboolean*);
void (*ReleaseStringCritical)(JNIEnv*, jstring, const jchar*);
//创建弱全局引用
jweak (*NewWeakGlobalRef)(JNIEnv*, jobject);
//删除弱全局引用
void (*DeleteWeakGlobalRef)(JNIEnv*, jweak);
//异常检查
jboolean (*ExceptionCheck)(JNIEnv*);
//分配并返回一个直接的java.nio.ByteBuffer
jobject (*NewDirectByteBuffer)(JNIEnv*, void*, jlong);
//获取并返回给定直接java.nio.Buffer引用的内存区域的起始地址
void* (*GetDirectBufferAddress)(JNIEnv*, jobject);
//获取并返回给定直接java.nio.Buffer引用的内存区域的容量。容量是内存区域包含的元素数
jlong (*GetDirectBufferCapacity)(JNIEnv*, jobject);
/* added in JNI 1.6 */
//返回obj参数引用的对象的类型
jobjectRefType (*GetObjectRefType)(JNIEnv*, jobject);
}
这个结构体里面定义了所有native层的函数指针，这个结构体是JNINative的核心，经常用到的结构体JNIEnv和结构体JNIVM内部都会持有该结构体的。JNIEnv和JNIVM里面的所有操作，都是调用该结构体里面的函数指针。
四、JNIInvokeInterface结构体的定义
struct JNIInvokeInterface {
void* reserved0;
void* reserved1;
void* reserved2;
jint (*DestroyJavaVM)(JavaVM*);
jint (*AttachCurrentThread)(JavaVM*, JNIEnv**, void*);
jint (*DetachCurrentThread)(JavaVM*);
jint (*GetEnv)(JavaVM*, void**, jint);
jint (*AttachCurrentThreadAsDaemon)(JavaVM*, JNIEnv**, void*);
};
DestroyJavaVM：销毁javaVM
AttachCurrentThread:绑定到当前线程
DetachCurrentThread：从当前线程分离
GetEnv：获取Env
AttachCurrentThreadAsDaemon:设置当前线程为守护线程
五、_JNIEnv结构体的定义
struct _JNIEnv {
/* do not rename this; it does not seem to be entirely opaque */
const struct JNINativeInterface* functions;
#if defined(__cplusplus)
jint GetVersion()
{ return functions->GetVersion(this); }
jclass DefineClass(const char *name, jobject loader, const jbyte* buf,
jsize bufLen)
{ return functions->DefineClass(this, name, loader, buf, bufLen); }
jclass FindClass(const char* name)
{ return functions->FindClass(this, name); }
jmethodID FromReflectedMethod(jobject method)
{ return functions->FromReflectedMethod(this, method); }
jfieldID FromReflectedField(jobject field)
{ return functions->FromReflectedField(this, field); }
jobject ToReflectedMethod(jclass cls, jmethodID methodID, jboolean isStatic)
{ return functions->ToReflectedMethod(this, cls, methodID, isStatic); }
jclass GetSuperclass(jclass clazz)
{ return functions->GetSuperclass(this, clazz); }
jboolean IsAssignableFrom(jclass clazz1, jclass clazz2)
{ return functions->IsAssignableFrom(this, clazz1, clazz2); }
jobject ToReflectedField(jclass cls, jfieldID fieldID, jboolean isStatic)
{ return functions->ToReflectedField(this, cls, fieldID, isStatic); }
jint Throw(jthrowable obj)
{ return functions->Throw(this, obj); }
jint ThrowNew(jclass clazz, const char* message)
{ return functions->ThrowNew(this, clazz, message); }
jthrowable ExceptionOccurred()
{ return functions->ExceptionOccurred(this); }
void ExceptionDescribe()
{ functions->ExceptionDescribe(this); }
void ExceptionClear()
{ functions->ExceptionClear(this); }
void FatalError(const char* msg)
{ functions->FatalError(this, msg); }
jint PushLocalFrame(jint capacity)
{ return functions->PushLocalFrame(this, capacity); }
jobject PopLocalFrame(jobject result)
{ return functions->PopLocalFrame(this, result); }
jobject NewGlobalRef(jobject obj)
{ return functions->NewGlobalRef(this, obj); }
void DeleteGlobalRef(jobject globalRef)
{ functions->DeleteGlobalRef(this, globalRef); }
void DeleteLocalRef(jobject localRef)
{ functions->DeleteLocalRef(this, localRef); }
jboolean IsSameObject(jobject ref1, jobject ref2)
{ return functions->IsSameObject(this, ref1, ref2); }
jobject NewLocalRef(jobject ref)
{ return functions->NewLocalRef(this, ref); }
jint EnsureLocalCapacity(jint capacity)
{ return functions->EnsureLocalCapacity(this, capacity); }
jobject AllocObject(jclass clazz)
{ return functions->AllocObject(this, clazz); }
jobject NewObject(jclass clazz, jmethodID methodID, ...)
{
va_list args;
va_start(args, methodID);
jobject result = functions->NewObjectV(this, clazz, methodID, args);
va_end(args);
return result;
}
jobject NewObjectV(jclass clazz, jmethodID methodID, va_list args)
{ return functions->NewObjectV(this, clazz, methodID, args); }
jobject NewObjectA(jclass clazz, jmethodID methodID, const jvalue* args)
{ return functions->NewObjectA(this, clazz, methodID, args); }
jclass GetObjectClass(jobject obj)
{ return functions->GetObjectClass(this, obj); }
jboolean IsInstanceOf(jobject obj, jclass clazz)
{ return functions->IsInstanceOf(this, obj, clazz); }
jmethodID GetMethodID(jclass clazz, const char* name, const char* sig)
{ return functions->GetMethodID(this, clazz, name, sig); }
#define CALL_TYPE_METHOD(_jtype, _jname) \
_jtype Call##_jname##Method(jobject obj, jmethodID methodID, ...) \
{ \
_jtype result; \
va_list args; \
va_start(args, methodID); \
result = functions->Call##_jname##MethodV(this, obj, methodID, \
args); \
va_end(args); \
return result; \
}
#define CALL_TYPE_METHODV(_jtype, _jname) \
_jtype Call##_jname##MethodV(jobject obj, jmethodID methodID, \
va_list args) \
{ return functions->Call##_jname##MethodV(this, obj, methodID, args); }
#define CALL_TYPE_METHODA(_jtype, _jname) \
_jtype Call##_jname##MethodA(jobject obj, jmethodID methodID, \
const jvalue* args) \
{ return functions->Call##_jname##MethodA(this, obj, methodID, args); }
#define CALL_TYPE(_jtype, _jname) \
CALL_TYPE_METHOD(_jtype, _jname) \
CALL_TYPE_METHODV(_jtype, _jname) \
CALL_TYPE_METHODA(_jtype, _jname)
CALL_TYPE(jobject, Object)
CALL_TYPE(jboolean, Boolean)
CALL_TYPE(jbyte, Byte)
CALL_TYPE(jchar, Char)
CALL_TYPE(jshort, Short)
CALL_TYPE(jint, Int)
CALL_TYPE(jlong, Long)
CALL_TYPE(jfloat, Float)
CALL_TYPE(jdouble, Double)
void CallVoidMethod(jobject obj, jmethodID methodID, ...)
{
va_list args;
va_start(args, methodID);
functions->CallVoidMethodV(this, obj, methodID, args);
va_end(args);
}
void CallVoidMethodV(jobject obj, jmethodID methodID, va_list args)
{ functions->CallVoidMethodV(this, obj, methodID, args); }
void CallVoidMethodA(jobject obj, jmethodID methodID, const jvalue* args)
{ functions->CallVoidMethodA(this, obj, methodID, args); }
#define CALL_NONVIRT_TYPE_METHOD(_jtype, _jname) \
_jtype CallNonvirtual##_jname##Method(jobject obj, jclass clazz, \
jmethodID methodID, ...) \
{ \
_jtype result; \
va_list args; \
va_start(args, methodID); \
result = functions->CallNonvirtual##_jname##MethodV(this, obj, \
clazz, methodID, args); \
va_end(args); \
return result; \
}
#define CALL_NONVIRT_TYPE_METHODV(_jtype, _jname) \
_jtype CallNonvirtual##_jname##MethodV(jobject obj, jclass clazz, \
jmethodID methodID, va_list args) \
{ return functions->CallNonvirtual##_jname##MethodV(this, obj, clazz, \
methodID, args); }
#define CALL_NONVIRT_TYPE_METHODA(_jtype, _jname) \
_jtype CallNonvirtual##_jname##MethodA(jobject obj, jclass clazz, \
jmethodID methodID, const jvalue* args) \
{ return functions->CallNonvirtual##_jname##MethodA(this, obj, clazz, \
methodID, args); }
#define CALL_NONVIRT_TYPE(_jtype, _jname) \
CALL_NONVIRT_TYPE_METHOD(_jtype, _jname) \
CALL_NONVIRT_TYPE_METHODV(_jtype, _jname) \
CALL_NONVIRT_TYPE_METHODA(_jtype, _jname)
CALL_NONVIRT_TYPE(jobject, Object)
CALL_NONVIRT_TYPE(jboolean, Boolean)
CALL_NONVIRT_TYPE(jbyte, Byte)
CALL_NONVIRT_TYPE(jchar, Char)
CALL_NONVIRT_TYPE(jshort, Short)
CALL_NONVIRT_TYPE(jint, Int)
CALL_NONVIRT_TYPE(jlong, Long)
CALL_NONVIRT_TYPE(jfloat, Float)
CALL_NONVIRT_TYPE(jdouble, Double)
void CallNonvirtualVoidMethod(jobject obj, jclass clazz,
jmethodID methodID, ...)
{
va_list args;
va_start(args, methodID);
functions->CallNonvirtualVoidMethodV(this, obj, clazz, methodID, args);
va_end(args);
}
void CallNonvirtualVoidMethodV(jobject obj, jclass clazz,
jmethodID methodID, va_list args)
{ functions->CallNonvirtualVoidMethodV(this, obj, clazz, methodID, args); }
void CallNonvirtualVoidMethodA(jobject obj, jclass clazz,
jmethodID methodID, const jvalue* args)
{ functions->CallNonvirtualVoidMethodA(this, obj, clazz, methodID, args); }
jfieldID GetFieldID(jclass clazz, const char* name, const char* sig)
{ return functions->GetFieldID(this, clazz, name, sig); }
jobject GetObjectField(jobject obj, jfieldID fieldID)
{ return functions->GetObjectField(this, obj, fieldID); }
jboolean GetBooleanField(jobject obj, jfieldID fieldID)
{ return functions->GetBooleanField(this, obj, fieldID); }
jbyte GetByteField(jobject obj, jfieldID fieldID)
{ return functions->GetByteField(this, obj, fieldID); }
jchar GetCharField(jobject obj, jfieldID fieldID)
{ return functions->GetCharField(this, obj, fieldID); }
jshort GetShortField(jobject obj, jfieldID fieldID)
{ return functions->GetShortField(this, obj, fieldID); }
jint GetIntField(jobject obj, jfieldID fieldID)
{ return functions->GetIntField(this, obj, fieldID); }
jlong GetLongField(jobject obj, jfieldID fieldID)
{ return functions->GetLongField(this, obj, fieldID); }
jfloat GetFloatField(jobject obj, jfieldID fieldID)
{ return functions->GetFloatField(this, obj, fieldID); }
jdouble GetDoubleField(jobject obj, jfieldID fieldID)
{ return functions->GetDoubleField(this, obj, fieldID); }
void SetObjectField(jobject obj, jfieldID fieldID, jobject value)
{ functions->SetObjectField(this, obj, fieldID, value); }
void SetBooleanField(jobject obj, jfieldID fieldID, jboolean value)
{ functions->SetBooleanField(this, obj, fieldID, value); }
void SetByteField(jobject obj, jfieldID fieldID, jbyte value)
{ functions->SetByteField(this, obj, fieldID, value); }
void SetCharField(jobject obj, jfieldID fieldID, jchar value)
{ functions->SetCharField(this, obj, fieldID, value); }
void SetShortField(jobject obj, jfieldID fieldID, jshort value)
{ functions->SetShortField(this, obj, fieldID, value); }
void SetIntField(jobject obj, jfieldID fieldID, jint value)
{ functions->SetIntField(this, obj, fieldID, value); }
void SetLongField(jobject obj, jfieldID fieldID, jlong value)
{ functions->SetLongField(this, obj, fieldID, value); }
void SetFloatField(jobject obj, jfieldID fieldID, jfloat value)
{ functions->SetFloatField(this, obj, fieldID, value); }
void SetDoubleField(jobject obj, jfieldID fieldID, jdouble value)
{ functions->SetDoubleField(this, obj, fieldID, value); }
jmethodID GetStaticMethodID(jclass clazz, const char* name, const char* sig)
{ return functions->GetStaticMethodID(this, clazz, name, sig); }
#define CALL_STATIC_TYPE_METHOD(_jtype, _jname) \
_jtype CallStatic##_jname##Method(jclass clazz, jmethodID methodID, \
...) \
{ \
_jtype result; \
va_list args; \
va_start(args, methodID); \
result = functions->CallStatic##_jname##MethodV(this, clazz, \
methodID, args); \
va_end(args); \
return result; \
}
#define CALL_STATIC_TYPE_METHODV(_jtype, _jname) \
_jtype CallStatic##_jname##MethodV(jclass clazz, jmethodID methodID, \
va_list args) \
{ return functions->CallStatic##_jname##MethodV(this, clazz, methodID, \
args); }
#define CALL_STATIC_TYPE_METHODA(_jtype, _jname) \
_jtype CallStatic##_jname##MethodA(jclass clazz, jmethodID methodID, \
const jvalue* args) \
{ return functions->CallStatic##_jname##MethodA(this, clazz, methodID, \
args); }
#define CALL_STATIC_TYPE(_jtype, _jname) \
CALL_STATIC_TYPE_METHOD(_jtype, _jname) \
CALL_STATIC_TYPE_METHODV(_jtype, _jname) \
CALL_STATIC_TYPE_METHODA(_jtype, _jname)
CALL_STATIC_TYPE(jobject, Object)
CALL_STATIC_TYPE(jboolean, Boolean)
CALL_STATIC_TYPE(jbyte, Byte)
CALL_STATIC_TYPE(jchar, Char)
CALL_STATIC_TYPE(jshort, Short)
CALL_STATIC_TYPE(jint, Int)
CALL_STATIC_TYPE(jlong, Long)
CALL_STATIC_TYPE(jfloat, Float)
CALL_STATIC_TYPE(jdouble, Double)
void CallStaticVoidMethod(jclass clazz, jmethodID methodID, ...)
{
va_list args;
va_start(args, methodID);
functions->CallStaticVoidMethodV(this, clazz, methodID, args);
va_end(args);
}
void CallStaticVoidMethodV(jclass clazz, jmethodID methodID, va_list args)
{ functions->CallStaticVoidMethodV(this, clazz, methodID, args); }
void CallStaticVoidMethodA(jclass clazz, jmethodID methodID, const jvalue* args)
{ functions->CallStaticVoidMethodA(this, clazz, methodID, args); }
jfieldID GetStaticFieldID(jclass clazz, const char* name, const char* sig)
{ return functions->GetStaticFieldID(this, clazz, name, sig); }
jobject GetStaticObjectField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticObjectField(this, clazz, fieldID); }
jboolean GetStaticBooleanField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticBooleanField(this, clazz, fieldID); }
jbyte GetStaticByteField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticByteField(this, clazz, fieldID); }
jchar GetStaticCharField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticCharField(this, clazz, fieldID); }
jshort GetStaticShortField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticShortField(this, clazz, fieldID); }
jint GetStaticIntField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticIntField(this, clazz, fieldID); }
jlong GetStaticLongField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticLongField(this, clazz, fieldID); }
jfloat GetStaticFloatField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticFloatField(this, clazz, fieldID); }
jdouble GetStaticDoubleField(jclass clazz, jfieldID fieldID)
{ return functions->GetStaticDoubleField(this, clazz, fieldID); }
void SetStaticObjectField(jclass clazz, jfieldID fieldID, jobject value)
{ functions->SetStaticObjectField(this, clazz, fieldID, value); }
void SetStaticBooleanField(jclass clazz, jfieldID fieldID, jboolean value)
{ functions->SetStaticBooleanField(this, clazz, fieldID, value); }
void SetStaticByteField(jclass clazz, jfieldID fieldID, jbyte value)
{ functions->SetStaticByteField(this, clazz, fieldID, value); }
void SetStaticCharField(jclass clazz, jfieldID fieldID, jchar value)
{ functions->SetStaticCharField(this, clazz, fieldID, value); }
void SetStaticShortField(jclass clazz, jfieldID fieldID, jshort value)
{ functions->SetStaticShortField(this, clazz, fieldID, value); }
void SetStaticIntField(jclass clazz, jfieldID fieldID, jint value)
{ functions->SetStaticIntField(this, clazz, fieldID, value); }
void SetStaticLongField(jclass clazz, jfieldID fieldID, jlong value)
{ functions->SetStaticLongField(this, clazz, fieldID, value); }
void SetStaticFloatField(jclass clazz, jfieldID fieldID, jfloat value)
{ functions->SetStaticFloatField(this, clazz, fieldID, value); }
void SetStaticDoubleField(jclass clazz, jfieldID fieldID, jdouble value)
{ functions->SetStaticDoubleField(this, clazz, fieldID, value); }
jstring NewString(const jchar* unicodeChars, jsize len)
{ return functions->NewString(this, unicodeChars, len); }
jsize GetStringLength(jstring string)
{ return functions->GetStringLength(this, string); }
const jchar* GetStringChars(jstring string, jboolean* isCopy)
{ return functions->GetStringChars(this, string, isCopy); }
void ReleaseStringChars(jstring string, const jchar* chars)
{ functions->ReleaseStringChars(this, string, chars); }
jstring NewStringUTF(const char* bytes)
{ return functions->NewStringUTF(this, bytes); }
jsize GetStringUTFLength(jstring string)
{ return functions->GetStringUTFLength(this, string); }
const char* GetStringUTFChars(jstring string, jboolean* isCopy)
{ return functions->GetStringUTFChars(this, string, isCopy); }
void ReleaseStringUTFChars(jstring string, const char* utf)
{ functions->ReleaseStringUTFChars(this, string, utf); }
jsize GetArrayLength(jarray array)
{ return functions->GetArrayLength(this, array); }
jobjectArray NewObjectArray(jsize length, jclass elementClass,
jobject initialElement)
{ return functions->NewObjectArray(this, length, elementClass,
initialElement); }
jobject GetObjectArrayElement(jobjectArray array, jsize index)
{ return functions->GetObjectArrayElement(this, array, index); }
void SetObjectArrayElement(jobjectArray array, jsize index, jobject value)
{ functions->SetObjectArrayElement(this, array, index, value); }
jbooleanArray NewBooleanArray(jsize length)
{ return functions->NewBooleanArray(this, length); }
jbyteArray NewByteArray(jsize length)
{ return functions->NewByteArray(this, length); }
jcharArray NewCharArray(jsize length)
{ return functions->NewCharArray(this, length); }
jshortArray NewShortArray(jsize length)
{ return functions->NewShortArray(this, length); }
jintArray NewIntArray(jsize length)
{ return functions->NewIntArray(this, length); }
jlongArray NewLongArray(jsize length)
{ return functions->NewLongArray(this, length); }
jfloatArray NewFloatArray(jsize length)
{ return functions->NewFloatArray(this, length); }
jdoubleArray NewDoubleArray(jsize length)
{ return functions->NewDoubleArray(this, length); }
jboolean* GetBooleanArrayElements(jbooleanArray array, jboolean* isCopy)
{ return functions->GetBooleanArrayElements(this, array, isCopy); }
jbyte* GetByteArrayElements(jbyteArray array, jboolean* isCopy)
{ return functions->GetByteArrayElements(this, array, isCopy); }
jchar* GetCharArrayElements(jcharArray array, jboolean* isCopy)
{ return functions->GetCharArrayElements(this, array, isCopy); }
jshort* GetShortArrayElements(jshortArray array, jboolean* isCopy)
{ return functions->GetShortArrayElements(this, array, isCopy); }
jint* GetIntArrayElements(jintArray array, jboolean* isCopy)
{ return functions->GetIntArrayElements(this, array, isCopy); }
jlong* GetLongArrayElements(jlongArray array, jboolean* isCopy)
{ return functions->GetLongArrayElements(this, array, isCopy); }
jfloat* GetFloatArrayElements(jfloatArray array, jboolean* isCopy)
{ return functions->GetFloatArrayElements(this, array, isCopy); }
jdouble* GetDoubleArrayElements(jdoubleArray array, jboolean* isCopy)
{ return functions->GetDoubleArrayElements(this, array, isCopy); }
void ReleaseBooleanArrayElements(jbooleanArray array, jboolean* elems,
jint mode)
{ functions->ReleaseBooleanArrayElements(this, array, elems, mode); }
void ReleaseByteArrayElements(jbyteArray array, jbyte* elems,
jint mode)
{ functions->ReleaseByteArrayElements(this, array, elems, mode); }
void ReleaseCharArrayElements(jcharArray array, jchar* elems,
jint mode)
{ functions->ReleaseCharArrayElements(this, array, elems, mode); }
void ReleaseShortArrayElements(jshortArray array, jshort* elems,
jint mode)
{ functions->ReleaseShortArrayElements(this, array, elems, mode); }
void ReleaseIntArrayElements(jintArray array, jint* elems,
jint mode)
{ functions->ReleaseIntArrayElements(this, array, elems, mode); }
void ReleaseLongArrayElements(jlongArray array, jlong* elems,
jint mode)
{ functions->ReleaseLongArrayElements(this, array, elems, mode); }
void ReleaseFloatArrayElements(jfloatArray array, jfloat* elems,
jint mode)
{ functions->ReleaseFloatArrayElements(this, array, elems, mode); }
void ReleaseDoubleArrayElements(jdoubleArray array, jdouble* elems,
jint mode)
{ functions->ReleaseDoubleArrayElements(this, array, elems, mode); }
void GetBooleanArrayRegion(jbooleanArray array, jsize start, jsize len,
jboolean* buf)
{ functions->GetBooleanArrayRegion(this, array, start, len, buf); }
void GetByteArrayRegion(jbyteArray array, jsize start, jsize len,
jbyte* buf)
{ functions->GetByteArrayRegion(this, array, start, len, buf); }
void GetCharArrayRegion(jcharArray array, jsize start, jsize len,
jchar* buf)
{ functions->GetCharArrayRegion(this, array, start, len, buf); }
void GetShortArrayRegion(jshortArray array, jsize start, jsize len,
jshort* buf)
{ functions->GetShortArrayRegion(this, array, start, len, buf); }
void GetIntArrayRegion(jintArray array, jsize start, jsize len,
jint* buf)
{ functions->GetIntArrayRegion(this, array, start, len, buf); }
void GetLongArrayRegion(jlongArray array, jsize start, jsize len,
jlong* buf)
{ functions->GetLongArrayRegion(this, array, start, len, buf); }
void GetFloatArrayRegion(jfloatArray array, jsize start, jsize len,
jfloat* buf)
{ functions->GetFloatArrayRegion(this, array, start, len, buf); }
void GetDoubleArrayRegion(jdoubleArray array, jsize start, jsize len,
jdouble* buf)
{ functions->GetDoubleArrayRegion(this, array, start, len, buf); }
void SetBooleanArrayRegion(jbooleanArray array, jsize start, jsize len,
const jboolean* buf)
{ functions->SetBooleanArrayRegion(this, array, start, len, buf); }
void SetByteArrayRegion(jbyteArray array, jsize start, jsize len,
const jbyte* buf)
{ functions->SetByteArrayRegion(this, array, start, len, buf); }
void SetCharArrayRegion(jcharArray array, jsize start, jsize len,
const jchar* buf)
{ functions->SetCharArrayRegion(this, array, start, len, buf); }
void SetShortArrayRegion(jshortArray array, jsize start, jsize len,
const jshort* buf)
{ functions->SetShortArrayRegion(this, array, start, len, buf); }
void SetIntArrayRegion(jintArray array, jsize start, jsize len,
const jint* buf)
{ functions->SetIntArrayRegion(this, array, start, len, buf); }
void SetLongArrayRegion(jlongArray array, jsize start, jsize len,
const jlong* buf)
{ functions->SetLongArrayRegion(this, array, start, len, buf); }
void SetFloatArrayRegion(jfloatArray array, jsize start, jsize len,
const jfloat* buf)
{ functions->SetFloatArrayRegion(this, array, start, len, buf); }
void SetDoubleArrayRegion(jdoubleArray array, jsize start, jsize len,
const jdouble* buf)
{ functions->SetDoubleArrayRegion(this, array, start, len, buf); }
jint RegisterNatives(jclass clazz, const JNINativeMethod* methods,
jint nMethods)
{ return functions->RegisterNatives(this, clazz, methods, nMethods); }
jint UnregisterNatives(jclass clazz)
{ return functions->UnregisterNatives(this, clazz); }
jint MonitorEnter(jobject obj)
{ return functions->MonitorEnter(this, obj); }
jint MonitorExit(jobject obj)
{ return functions->MonitorExit(this, obj); }
jint GetJavaVM(JavaVM** vm)
{ return functions->GetJavaVM(this, vm); }
void GetStringRegion(jstring str, jsize start, jsize len, jchar* buf)
{ functions->GetStringRegion(this, str, start, len, buf); }
void GetStringUTFRegion(jstring str, jsize start, jsize len, char* buf)
{ return functions->GetStringUTFRegion(this, str, start, len, buf); }
void* GetPrimitiveArrayCritical(jarray array, jboolean* isCopy)
{ return functions->GetPrimitiveArrayCritical(this, array, isCopy); }
void ReleasePrimitiveArrayCritical(jarray array, void* carray, jint mode)
{ functions->ReleasePrimitiveArrayCritical(this, array, carray, mode); }
const jchar* GetStringCritical(jstring string, jboolean* isCopy)
{ return functions->GetStringCritical(this, string, isCopy); }
void ReleaseStringCritical(jstring string, const jchar* carray)
{ functions->ReleaseStringCritical(this, string, carray); }
jweak NewWeakGlobalRef(jobject obj)
{ return functions->NewWeakGlobalRef(this, obj); }
void DeleteWeakGlobalRef(jweak obj)
{ functions->DeleteWeakGlobalRef(this, obj); }
jboolean ExceptionCheck()
{ return functions->ExceptionCheck(this); }
jobject NewDirectByteBuffer(void* address, jlong capacity)
{ return functions->NewDirectByteBuffer(this, address, capacity); }
void* GetDirectBufferAddress(jobject buf)
{ return functions->GetDirectBufferAddress(this, buf); }
jlong GetDirectBufferCapacity(jobject buf)
{ return functions->GetDirectBufferCapacity(this, buf); }
/* added in JNI 1.6 */
jobjectRefType GetObjectRefType(jobject obj)
{ return functions->GetObjectRefType(this, obj); }
#endif /*__cplusplus*/
};
从native世界进入java世界.java到native的桥梁是JNIEnv,我们只要获得一个JNIEnv就能进入到java世界了.突破点就在AndroidRuntime,android::AndroidRuntime::getJavaVM();这个静态方法能够获取一个JavaVM, JavaVM->GetEnv方法能够获得一个JNIEnv了.JNIEnv是和线程相关的,使用前一定记得将其附加到当前进程,也要在适当的时候将其销毁。
该内部持有JNINativeInterface，_JNIEnv里面所有的方法调用最终都是调用JNINativeInterface里面的
六、_JavaVM结构体的定义
struct _JavaVM {
const struct JNIInvokeInterface* functions;
#if defined(__cplusplus)
jint DestroyJavaVM()
{ return functions->DestroyJavaVM(this); }
jint AttachCurrentThread(JNIEnv** p_env, void* thr_args)
{ return functions->AttachCurrentThread(this, p_env, thr_args); }
jint DetachCurrentThread()
{ return functions->DetachCurrentThread(this); }
jint GetEnv(void** env, jint version)
{ return functions->GetEnv(this, env, version); }
jint AttachCurrentThreadAsDaemon(JNIEnv** p_env, void* thr_args)
{ return functions->AttachCurrentThreadAsDaemon(this, p_env, thr_args); }
#endif /*__cplusplus*/
};
JavaVM是虚拟机在JNI中的表示，一个JVM中只有一个JavaVM对象，这个对象是线程共享的。java虚拟机，该结构体内持有JNIInvokeInterface，所有的操作都是JNIInvokeInterface实现的。
七、JavaVMAttachArgs结构体的定义
struct JavaVMAttachArgs {
jint version; /* must be >= JNI_VERSION_1_2 */
const char* name; /* NULL or name of thread as modified UTF-8 str */
jobject group; /* global ref of a ThreadGroup object, or NULL */
};
typedef struct JavaVMAttachArgs JavaVMAttachArgs;
绑定JavaVm的参数结构体
八、JavaVMOption结构体的定义
/*
* JNI 1.2+ initialization. (As of 1.6, the pre-1.2 structures are no
* longer supported.)
*/
typedef struct JavaVMOption {
const char* optionString;
void* extraInfo;
} JavaVMOption;
九、JavaVMInitArgs结构体的定义
typedef struct JavaVMInitArgs {
jint version; /* use JNI_VERSION_1_2 or later */
jint nOptions;
JavaVMOption* options;
jboolean ignoreUnrecognized;
} JavaVMInitArgs;
存放虚拟机参数的结构体
十、JNI_OnLoad方法的定义
JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved);
JNI挂载的时候，会调用该方法，通常动态注册native方法的时候，会重写该方法，在该方法里面注册native方法。
十一、JNI_OnUnload方法的定义
JNIEXPORT void JNI_OnUnload(JavaVM* vm, void* reserved);
JNI卸载的时候会调用该方法，通常用来释放native相关的资源
JNI官网地址
jni.h的头文件所在源码目录：
prebuilts/ndk/current/platforms/android-21/arch-x86/usr/include
jni.cpp文件所在的源码目录：
4.4版本之前：
/dalvik/vm/Jni.cpp
4.4版本之后：
art/runtime/jni_internal.cc