Why am I getting a redefinition error?

I'm following the tutorial here: http://iphone-3d-programming.labs.oreilly.com/ch01.html#ch01_id36002837

When I try to run the program, I get an error saying "Redefinition of 'void RenderingEngine1::OnRotate(DeviceOrientation)"

Here's the code. The function is at the end of it:

#include <OpenGLES/ES1/gl.h>
#include <OpenGLES/ES1/glext.h>
#include "IRenderingEngine.hpp"

class RenderingEngine1 : public IRenderingEngine {
public:
    RenderingEngine1();
    void Initialize(int width, int height);
    void Render() const;
    void UpdateAnimation(float timeStep) {}
    void OnRotate(DeviceOrientation orientation) {}
private:
    float m_currentAngle;
    GLuint m_framebuffer;
    GLuint m_renderbuffer;
};

IRenderingEngine* CreateRenderer1()
{
    return new RenderingEngine1();
}

struct Vertex {
    float Position[2];
    float Color[4];
};

// Define the positions and colors of two triangles.
const Vertex Vertices[] = {
    {{-0.5, -0.866}, {1, 1, 0.5f, 1}},
    {{0.5, -0.866},  {1, 1, 0.5f, 1}},
    {{0, 1},         {1, 1, 0.5f, 1}},
    {{-0.5, -0.866}, {0.5f, 0.5f, 0.5f}},
    {{0.5, -0.866},  {0.5f, 0.5f, 0.5f}},
    {{0, -0.4f},     {0.5f, 0.5f, 0.5f}},
};

RenderingEngine1::RenderingEngine1()
{
    glGenRenderbuffersOES(1, &m_renderbuffer);
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, m_renderbuffer);
}

void RenderingEngine1::Initialize(int width, int height)
{
    // Create the framebuffer object and attach the color buffer.
    glGenFramebuffersOES(1, &m_framebuffer);
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, m_framebuffer);
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES,
                                 GL_COLOR_ATTACHMENT0_OES,
                                 GL_RENDERBUFFER_OES,
                                 m_renderbuffer);

    glViewport(0, 0, width, height);

    glMatrixMode(GL_PROJECTION);

    // Initialize the projection matrix.
    const float maxX = 2;
    const float maxY = 3;
    glOrthof(-maxX, +maxX, -maxY, +maxY, -1, 1);

    glMatrixMode(GL_MODELVIEW);
}

void RenderingEngine1::Render() const
{
    glClearColor(0.5f, 0.5f, 0.5f, 1);
    glClear(GL_COLOR_BUFFER_BIT);

    glPushMatrix();
    glRotatef(m_currentAngle, 0, 0, 1);

    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);

    glVertexPointer(2, GL_FLOAT, sizeof(Vertex), &Vertices[0].Position[0]);
    glColorPointer(4, GL_FLOAT, sizeof(Vertex), &Vertices[0].Color[0]);

    GLsizei vertexCount = sizeof(Vertices) / sizeof(Vertex);
    glDrawArrays(GL_TRIANGLES, 0, vertexCount);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);

    glPopMatrix();
}

void RenderingEngine1::OnRotate(DeviceOrientation orientation)
{
    float angle = 0;

    switch (orientation) {
        case DeviceOrientationLandscapeLeft:
            angle = 270;
            break;

        case DeviceOrientationPortraitUpsideDown:
            angle = 180;
            break;

        case DeviceOrientationLandscapeRight:
            angle = 90;
            break;
    }

    m_currentAngle开发者_如何学JAVA = angle;
}

remove the body

class RenderingEngine1 : public IRenderingEngine {
public:
...
    void OnRotate(DeviceOrientation orientation) {}
...
->   void OnRotate(DeviceOrientation orientation);