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JNI方法简介及实例

JNI方法简介及实例

作者: 码上述Andy | 来源:发表于2019-06-29 00:24 被阅读3次

这里讲到的JNI方法是指JNIEnv方法指针所指向的结构体（JNINativeInterface）一些函数。以下是jni.h头文件的方法声明：

struct JNINativeInterface {
    void*       reserved0;
    void*       reserved1;
    void*       reserved2;
    void*       reserved3;

    jint        (*GetVersion)(JNIEnv *);

    jclass      (*DefineClass)(JNIEnv*, const char*, jobject, const jbyte*,
                        jsize);
    jclass      (*FindClass)(JNIEnv*, const char*);

    jmethodID   (*FromReflectedMethod)(JNIEnv*, jobject);
    jfieldID    (*FromReflectedField)(JNIEnv*, jobject);
    /* spec doesn't show jboolean parameter */
    jobject     (*ToReflectedMethod)(JNIEnv*, jclass, jmethodID, jboolean);

    jclass      (*GetSuperclass)(JNIEnv*, jclass);
    jboolean    (*IsAssignableFrom)(JNIEnv*, jclass, jclass);

    /* spec doesn't show jboolean parameter */
    jobject     (*ToReflectedField)(JNIEnv*, jclass, jfieldID, jboolean);

    jint        (*Throw)(JNIEnv*, jthrowable);
    jint        (*ThrowNew)(JNIEnv *, jclass, const char *);
    jthrowable  (*ExceptionOccurred)(JNIEnv*);
    void        (*ExceptionDescribe)(JNIEnv*);
    void        (*ExceptionClear)(JNIEnv*);
    void        (*FatalError)(JNIEnv*, const char*);

    jint        (*PushLocalFrame)(JNIEnv*, jint);
    jobject     (*PopLocalFrame)(JNIEnv*, jobject);

    jobject     (*NewGlobalRef)(JNIEnv*, jobject);
    void        (*DeleteGlobalRef)(JNIEnv*, jobject);
    void        (*DeleteLocalRef)(JNIEnv*, jobject);
    jboolean    (*IsSameObject)(JNIEnv*, jobject, jobject);

    jobject     (*NewLocalRef)(JNIEnv*, jobject);
    jint        (*EnsureLocalCapacity)(JNIEnv*, jint);

    jobject     (*AllocObject)(JNIEnv*, jclass);
    jobject     (*NewObject)(JNIEnv*, jclass, jmethodID, ...);
    jobject     (*NewObjectV)(JNIEnv*, jclass, jmethodID, va_list);
    jobject     (*NewObjectA)(JNIEnv*, jclass, jmethodID, const jvalue*);

    jclass      (*GetObjectClass)(JNIEnv*, jobject);
    jboolean    (*IsInstanceOf)(JNIEnv*, jobject, jclass);
    jmethodID   (*GetMethodID)(JNIEnv*, jclass, const char*, const char*);

    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*);

    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*);

    jfieldID    (*GetFieldID)(JNIEnv*, jclass, const char*, const char*);

    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);

    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);

    jmethodID   (*GetStaticMethodID)(JNIEnv*, jclass, const char*, const char*);

    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*);

    jfieldID    (*GetStaticFieldID)(JNIEnv*, jclass, const char*,
                        const char*);

    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);

    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);

    jstring     (*NewString)(JNIEnv*, const jchar*, jsize);
    jsize       (*GetStringLength)(JNIEnv*, jstring);
    const jchar* (*GetStringChars)(JNIEnv*, jstring, jboolean*);
    void        (*ReleaseStringChars)(JNIEnv*, jstring, const jchar*);
    jstring     (*NewStringUTF)(JNIEnv*, const char*);
    jsize       (*GetStringUTFLength)(JNIEnv*, jstring);
    /* JNI spec says this returns const jbyte*, but that's inconsistent */
    const char* (*GetStringUTFChars)(JNIEnv*, jstring, jboolean*);
    void        (*ReleaseStringUTFChars)(JNIEnv*, jstring, const char*);
    jsize       (*GetArrayLength)(JNIEnv*, jarray);
    jobjectArray (*NewObjectArray)(JNIEnv*, jsize, jclass, jobject);
    jobject     (*GetObjectArrayElement)(JNIEnv*, jobjectArray, jsize);
    void        (*SetObjectArrayElement)(JNIEnv*, jobjectArray, jsize, jobject);

    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);

    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*);

    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);

    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 */
    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*);

    jint        (*RegisterNatives)(JNIEnv*, jclass, const JNINativeMethod*,
                        jint);
    jint        (*UnregisterNatives)(JNIEnv*, jclass);
    jint        (*MonitorEnter)(JNIEnv*, jobject);
    jint        (*MonitorExit)(JNIEnv*, jobject);
    jint        (*GetJavaVM)(JNIEnv*, JavaVM**);

    void        (*GetStringRegion)(JNIEnv*, jstring, jsize, jsize, jchar*);
    void        (*GetStringUTFRegion)(JNIEnv*, jstring, jsize, jsize, char*);

    void*       (*GetPrimitiveArrayCritical)(JNIEnv*, jarray, jboolean*);
    void        (*ReleasePrimitiveArrayCritical)(JNIEnv*, jarray, void*, jint);

    const jchar* (*GetStringCritical)(JNIEnv*, jstring, jboolean*);
    void        (*ReleaseStringCritical)(JNIEnv*, jstring, const jchar*);

    jweak       (*NewWeakGlobalRef)(JNIEnv*, jobject);
    void        (*DeleteWeakGlobalRef)(JNIEnv*, jweak);

    jboolean    (*ExceptionCheck)(JNIEnv*);

    jobject     (*NewDirectByteBuffer)(JNIEnv*, void*, jlong);
    void*       (*GetDirectBufferAddress)(JNIEnv*, jobject);
    jlong       (*GetDirectBufferCapacity)(JNIEnv*, jobject);

    /* added in JNI 1.6 */
    jobjectRefType (*GetObjectRefType)(JNIEnv*, jobject);
};

以下列举的函数操作为jni.h头文件里部分函数说明和举例。

1.方法操作

1.1 jmethodID (GetStaticMethodID)(JNIEnv, jclass, const char, const char);

说明：获取方法ID
参数：JNIEnv：函数结构体指针，jclass：java层当前对象, char: 参数类型签名描述
返回：jmethodID：方法id
例如：

jmethodID jmethodID3 = env->GetStaticMethodID(jclass1, "fromNativeJNI3",
                                                  "(Ljava/lang/String;)V");

1.2 jobject (CallObjectMethod)(JNIEnv, jobject, jmethodID, ...);

说明：调用Object方法
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象
返回：jclass：class对象

1.3 jboolean (CallBooleanMethod)(JNIEnv, jobject, jmethodID, ...);

说明：调用Object方法
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象
返回：jclass：class对象

1.4 void (CallVoidMethod)(JNIEnv, jobject, jmethodID, ...);

说明：调用Object方法
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象
返回：jclass：class对象

1.5 void (CallStaticVoidMethod)(JNIEnv, jclass, jmethodID, ...);

说明：调用Object方法
参数：JNIEnv*：函数结构体指针，jclass：java层当前对象的类， jmethodID：方法id
返回：void：返回void
例如：

env->CallStaticVoidMethod(jclass1, jmethodID3, message2);

2.域操作

2.1 jfieldID (GetFieldID)(JNIEnv, jclass, const char, const char);

说明：获取域id（java变/常量）
参数：JNIEnv：函数结构体指针，jclass：java层当前对象的类，char：域名称， char*：域类型描述
返回：void：返回void

2.2 jobject (GetObjectField)(JNIEnv, jobject, jfieldID);

说明：获取Object域id
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象，jfieldID: 域id

2.3 void (SetObjectField)(JNIEnv, jobject, jfieldID, jobject);

说明：设置该域id对应的值
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象，jfieldID：域id， jobject：object类型的域值

2.41 void (SetBooleanField)(JNIEnv, jobject, jfieldID, jboolean);

说明：设置该域id对应boolean值
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象，jfieldID：域id， jboolean：boolean类型的域值
例如：

jfieldID jfieldID2 = env->GetFieldID(jclass1, "i", "I");
env->SetIntField(jobject2, jfieldID2, 200);

3.数组操作

3.1 jbooleanArray (NewBooleanArray)(JNIEnv, jsize);

说明：新建boolean数组
参数：JNIEnv*：函数结构体指针，jsize：当前数组大小
例如：

env->NewBooleanArray(env, 10);

3.2 jboolean* (GetBooleanArrayElements)(JNIEnv, jbooleanArray, jboolean*);

说明：获取boolean数组
参数：JNIEnv*：函数结构体指针，jbooleanArray：boolean数组引用
例如：

env->GetBooleanArrayElements(env, 10);

3.3 void (ReleaseIntArrayElements)(JNIEnv, jintArray, jint*, jint mode);

说明：释放数组
参数：JNIEnv*：函数结构体指针，jintArray：int数组引用, mode:释放模式

4.对象操作

4.1jobject (NewObject)(JNIEnv, jclass, jmethodID, ...);

说明：新建对象
参数：JNIEnv*：函数结构体指针，jclass：当前类，jmethodID：方法id

4.2 jboolean (IsInstanceOf)(JNIEnv, jobject, jclass);

说明：是否是指定的对象
参数：JNIEnv*：函数结构体指针，jobject：当前类的对象

4.3 jboolean (IsSameObject)(JNIEnv, jobject obj, jobject obj2);

说明：对比两个对象是否相同
参数：JNIEnv*：函数结构体指针，obj, obj2：比较的两个对象

5.类操作

5.1 jclass (GetObjectClass)(JNIEnv, jobject);

说明：获取对象实例
参数：JNIEnv*：函数结构体指针，jobject：java层当前对象
例如：

jclass jclazz = env->GetObjectClass(jobj);

5.2 jclass (FindClass)(JNIEnv, const char*);

说明：获取对象实例
参数：JNIEnv：函数结构体指针，char：java层对象完整路径
例如：

jclass jclazz = env->FindClass("jni/chowen/com/nativeapp/CInterface");

5.3 jclass (GetSuperclass)(JNIEnv, jclass);

说明：获取对象实例
参数：JNIEnv*：函数结构体指针，jclass：java层当前对象

6.异常操作

6.1 jint (*ThrowNew)(JNIEnv *, jclass, const char *);

说明：抛出异常
参数：char *：抛出异常信息
例如：

const char* c = env->GetStringUTFChars(jstring1, 0);
env->ThrowNew(jclass1, c)

6.2 jthrowable (ExceptionOccurred)(JNIEnv);

说明：是否发生异常

6.3 void (ExceptionDescribe)(JNIEnv);

说明：异常描述

6.4 void (ExceptionClear)(JNIEnv);

说明：清除异常

6.5 void (FatalError)(JNIEnv, const char*);

说明：抛出致命错误
参数：char *：抛出致命错误信息
例如：

const char* c = env->GetStringUTFChars(jstring1, 0);
env->FatalError(c); // 抛出一个致命异常

7.字符串操作

7.1jstring (NewString)(JNIEnv, const jchar*, jsize);

说明：新建字符，以UTF-16方式
参数：char *：字符，jsize：字符长度

7.2jstring (NewStringUTF)(JNIEnv, const char*);

说明：新建字符，以UTF-8方式
参数：char *：字符串

7.3jsize (GetStringLength)(JNIEnv, jstring);

7.4jsize (GetStringUTFLength)(JNIEnv, jstring);

说明：获取字符长度，7.3/4分别以UTF-16,UTF-8编码方式
参数：jstring ：字符串

7.5const jchar* (GetStringChars)(JNIEnv, jstring, jboolean* iscopy);

说明：java的字符串转换成c风格的字符，以UTF-16编码方式
参数：jstring ：字符, jboolean* iscopy:是否进行拷贝

7.6const char* (GetStringUTFChars)(JNIEnv, jstring, jboolean*);

说明：java的字符串转换成c风格的字符，以UTF-8编码方式
参数：jstring ：字符串, jboolean* iscopy:是否进行拷贝

7.7void (ReleaseStringChars)(JNIEnv, jstring, const jchar*);

说明：释放字符串引用
参数：jstring ：对应java字符串, const jchar*:c/c++字符串指针

8.引用与释放

8.1 创建引用

jobject (NewLocalRef)(JNIEnv, jobject obj);
jobject (NewGlobalRef)(JNIEnv, jobject obj);
jweak (NewWeakGlobalRef)(JNIEnv, jobject obj);
说明：创建局部/全局/全局弱引用
参数： jobject obj ：对象实例

8.2 释放引用

void (DeleteLocalRef)(JNIEnv, jobject);
void (DeleteGlobalRef)(JNIEnv, jobject);
void (DeleteWeakGlobalRef)(JNIEnv, jweak);
说明：释放局部/全局/全局弱引用
参数： jobject obj ：对象实例

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