打开GL矩形

Question

我需要对这段代码提供一点帮助......我已经在developer.android之后完成了它，但它仍然无法正常工作！显示问题。只有绿屏，没有任何矩形。有人能帮我吗？感谢：！）

public class Paddle 
{
    private FloatBuffer vertexBuffer;
    private ShortBuffer drawListBuffer;
    private int mProgram;

    public static int loadShader(int type, String shaderCode){

        int shader = GLES20.glCreateShader(type);
        GLES20.glShaderSource(shader, shaderCode);
        GLES20.glCompileShader(shader);

        return shader;
    }

    private final String vertexShaderCode =
            "attribute vec4 vPosition;" +
                    "void main() {" +
                    "  gl_Position = vPosition;" +
                    "}";

    private final String fragmentShaderCode =
            "precision mediump float;" +
                    "uniform vec4 vColor;" +
                    "void main() {" +
                    "  gl_FragColor = vColor;" +
                    "}";


    static final int COORDS_PER_VERTEX = 3;

    static float squareCoords[] = {
            -0.5f,  0.5f, 0.0f,
            -0.5f, -0.5f, 0.0f,
            0.5f, -0.5f, 0.0f,
            0.5f,  0.5f, 0.0f };

    private short drawOrder[] = { 0, 1, 2, 0, 2, 3 };

    private float color[] = {1, 1, 1, 1};

    private int mPositionHandle;
    private int mColorHandle;

    private final int vertexCount = squareCoords.length / COORDS_PER_VERTEX;
    private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex

    public Paddle()
    {

        ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4);
        bb.order(ByteOrder.nativeOrder());
        vertexBuffer = bb.asFloatBuffer();
        vertexBuffer.put(squareCoords);
        vertexBuffer.position(0);

        ByteBuffer dlb = ByteBuffer.allocate(drawOrder.length * 2);
        dlb.order(ByteOrder.nativeOrder());
        drawListBuffer = dlb.asShortBuffer();
        drawListBuffer.put(drawOrder);
        drawListBuffer.position(0);

        int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER,
                vertexShaderCode);
        int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER,
                fragmentShaderCode);
        mProgram = GLES20.glCreateProgram();

        GLES20.glAttachShader(mProgram, vertexShader);
        GLES20.glAttachShader(mProgram, fragmentShader);
        GLES20.glLinkProgram(mProgram);

    }

    public void draw()
    {
        GLES20.glUseProgram(mProgram);

        mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
        GLES20.glEnableVertexAttribArray(mPositionHandle);
        GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);

        mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
        GLES20.glUniform4fv(mColorHandle, 4, color, 0);
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
        GLES20.glDisableVertexAttribArray(mPositionHandle);

    }
}