Qt OpenGL DrawElements未绘制第二个三角形

现在，我正在按照Jamie King Qt OpenGL教程学习OpenGL。（他们很好）。

在其中一本教程中，我遵循它，但是无法使用DrawElemets绘制两个顶点缓冲区三角形。它与GLDrawArrays一起使用

请帮忙

提前致谢。

GLWidget.h

#ifndef _GL_WIDGET_H_
#define _GL_WIDGET_H_

#include <QtOpenGL\QGLWidget>

class GLWidget : public QGLWidget
{
public:

            GLWidget();
    virtual ~GLWidget();

protected:
    void initializeGL();
    void paintGL();
};
#endif

GLWidget.cpp
#include <gl\glew.h>
#include "globals.h"

#include "GLWidget.h"

using namespace std;

#define SIZE 1.0f


GLWidget::GLWidget()
{

}

GLWidget::~GLWidget()
{

}

// GLWindow Initialize function.
void GLWidget::initializeGL()
{


    // Initializing GLEW.
    GLenum err = glewInit();

    // Checking if the glew loads fine.
    if(err != GLEW_OK)
    {
        cerr<<"Cannot initialize GLEW: "<<err<<endl;
    }

    // Vertex Buffer storage space.
    GLuint vertBufferID;
    GLuint vertIndicesID;

    // Vertex array.
    GLfloat verts[] = 
    {
        // First traingle.
        +0.0f, +0.0f,   // 0
        +1.0f, +1.0f,   // 1    
        -1.0, +1.0,     // 2
        -1.0, -1.0,     // 3
        +1.0, -1.0,     // 4
    };

    // Creating the vertex buffer
    glGenBuffers(1, &vertBufferID);

    // binding the buffer.
    glBindBuffer(GL_ARRAY_BUFFER, vertBufferID);
    glBufferData(GL_ARRAY_BUFFER, sizeof(verts), &verts, GL_STATIC_DRAW);

    // Enalbing the position attribute of the vertex.
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);

    // Creating the vertex indices buffer.
    GLushort indices[] = { 0, 1, 2, 0, 3, 4}; 
    glGenBuffers(1, &vertIndicesID);

    // binding the buffer.
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vertIndicesID);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(vertIndicesID), indices, GL_STATIC_DRAW);
}

// GLWindow Paint Function.
void GLWidget::paintGL()
{

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    // Defining the viewport.
    glViewport(0, 0, width(), height());

    // Drawing the Triangle.
    //glDrawArrays(GL_TRIANGLES, 0, 6); 
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0); 
}