android java 层参数重载glVertexAttribPointer 在es20 C 接口中的处理方法

1. JNI jstring -> C char*    需要调用

const char * name = (const char *)env->GetStringUTFChars(js, false);


2. JNI jfloatArray -> C float []  需要：对数组进行遍历，在遍历中转换为自己的数组即可即是：
jfloat * tmpColor;//得到数组的jint size = env->GetArrayLength(c);int csize = (int)size;float color[(int)size];        //得到一个指向数组首地址的指针tmpColor = env->GetFloatArrayElements(c,false);for(int i=0; i< csize; i++){color[i] = *tmpColor ++;}


/*
*  问题描述：当用java调用es20的库的时候 自己实现native方法调用，其他方法都还好，有一个方法有重载，但是C接口里面只有一个方法glVertexAttribPointer ，jni传递的参*                        数又是buffer 和 int 两种所以就用了另外一个方法（glVertexAttribPointerBounds）来处理一下参数，并间接调用 glVertexAttribPointer 
*
*Java native 方法：
*/
// C function void glVertexAttribPointer ( GLuint indx, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const GLvoid *ptr );    private static native void glVertexAttribPointerBounds(int indx,int size,int type,boolean normalized,int stride,java.nio.Buffer ptr,int remaining);  public static void neuglVertexAttribPointer(int indx, int size, int type, boolean normalized, int stride, java.nio.Buffer ptr)  {    glVertexAttribPointerBounds(indx, size, type, normalized, stride, ptr, ptr.remaining());  }
/** C 接口中处理方法。 需要实现一个处理 buffer 的方法：getDirectBufferPointer**/void Java_com_drawtriangle_GLES20m_neuglVertexAttribPointer(JNIEnv * env, jclass jc, int indx, int size, int type, bool normaized, int stride, const void * pointer){    void(*fn)(int indx, int size, int type, bool normaized, int stride, const void * pointer);    fn = (void (*)(int, int, int, bool, int,const void *))dlsym(functionlib, "glVertexAttribPointer");    fn( indx,  size,  type,  normaized, stride, pointer);}static jclass bufferClass;static jfieldID positionID;static jfieldID elementSizeShiftID;static void * getDirectBufferPointer(JNIEnv *env, jobject buffer) {jclass IAEClassLocal = env->FindClass("java/lang/IllegalArgumentException");jclass bufferClassLocal = env->FindClass("java/nio/Buffer");bufferClass = (jclass) env->NewGlobalRef(bufferClassLocal);positionID = env->GetFieldID(bufferClass, "position", "I");jclass IAEClass = (jclass) env->NewGlobalRef(IAEClassLocal);elementSizeShiftID = env->GetFieldID(bufferClass, "_elementSizeShift", "I");char* buf = (char*) env->GetDirectBufferAddress(buffer);    if (buf) {        jint position = env->GetIntField(buffer, positionID);        jint elementSizeShift = env->GetIntField(buffer, elementSizeShiftID);        buf += position << elementSizeShift;    } else {        env->ThrowNew(IAEClass, "Must use a native order direct Buffer");    }    return (void *) buf;}void Java_com_drawtriangle_GLES20m_glVertexAttribPointerBounds(JNIEnv * env, jclass jc, jint index, jint size, jint type, jboolean normalized, jint stride, jobject pointer, jint remaining){jarray _array = (jarray) 0;jint _remaining;void *ptr = (void *) 0;if (pointer) {ptr = (void *) getDirectBufferPointer(env, pointer);if ( ! ptr ) {return;}}Java_com_drawtriangle_GLES20m_neuglVertexAttribPointer(env, jc, (int)index, (int)size, (int)type, (bool)normalized, (int)stride, ptr);}

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