Android OpenGLES绘图缓冲区，空白屏幕

Question

我试图使用FloatBuffer为我的顶点和索引的ShortBuffer绘制基元。一切正常，没有崩溃或警告，但屏幕是空白的。我可以毫不费力地使用glDrawTexfOES绘图。 如果有人可以看看代码我会很感激。

public abstract class PrimitiveBase extends DrawableEntity {
    protected float[] _vertices;
    protected short[] _indices;

    private FloatBuffer _verticesBuffer;
    private ShortBuffer _indicesBuffer;

    public PrimitiveBase(Sprite sprite, float x, float y) {
        super(sprite, x, y);

    }

    protected abstract void setVertices();

    @Override
    public void draw(float x, float y, float scaleX, float scaleY) {
        GL10 gl = GlSystem.getGl();

        gl.glPushMatrix();
        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glLoadIdentity();

        gl.glScalef(scaleX, scaleY, 1.0F);

        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

        gl.glVertexPointer(2, GL10.GL_FLOAT, 0, _verticesBuffer);
        gl.glColor4f(1.0F, 0, 0, 0);

        gl.glDrawElements(GL10.GL_TRIANGLES, _indices.length,
                GL10.GL_UNSIGNED_SHORT, _indicesBuffer);

        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);

        gl.glPushMatrix();
    }

    @Override
    public void load(EntityManager parent) {

        setVertices();

        ByteBuffer vbb = ByteBuffer.allocateDirect(_vertices.length * 4);
        vbb.order(ByteOrder.nativeOrder());
        _verticesBuffer = vbb.asFloatBuffer();

        _verticesBuffer.put(_vertices);
        _verticesBuffer.position(0);

        ByteBuffer ibb = ByteBuffer.allocateDirect(_indices.length * 2);
        ibb.order(ByteOrder.nativeOrder());
        _indicesBuffer = ibb.asShortBuffer();
        _indicesBuffer.put(_indices);
        _indicesBuffer.position(0);
    }

}

public class Rectangle extends PrimitiveBase {
    private float _width;
    private float _heigth;

    public Rectangle(Sprite sprite, float x, float y, float width, float height) {
        super(sprite, x, y);
        _heigth = height;
        _width = width;
    }

    @Override
    protected void setVertices() {
        _vertices = new float[8];
        _indices = new short[] { 0, 1, 2, 0, 2, 3 };

        _vertices[0] = getX() - (_width / 2);
        _vertices[1] = getY() + (_heigth / 2);

        _vertices[2] = getX() + (_width / 2);
        _vertices[3] = getY() + (_heigth / 2);

        _vertices[4] = getX() + (_width / 2);
        _vertices[5] = getY() - (_heigth / 2);

        _vertices[6] = getX() - (_width / 2);
        _vertices[7] = getY() - (_heigth / 2);

    }

}