Android Open Source - androidOpenGLShapes Square

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License

The source code is released under:

MIT License

Java Source Code

package com.example.opengl;
/*from ww  w. j a v  a  2s . co m*/
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

import android.opengl.GLES20;

public class Square {

  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;" +
      "}";
  
  
    private FloatBuffer vertexBuffer;
    private ShortBuffer drawListBuffer;
    private final int mProgram;
    private int mPositionHandle;
    private int mColorHandle;
    private int mMVPMatrixHandle;


    // number of coordinates per vertex in this array
    static final int COORDS_PER_VERTEX = 3;
    static float squareCoords[] = {
            -0.5f,  0.5f, 0.0f,   // top left
            -0.5f, -0.5f, 0.0f,   // bottom left
             0.5f, -0.5f, 0.0f,   // bottom right
             0.5f,  0.5f, 0.0f }; // top right

    private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices
    private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
    float color[] = { 0.2f, 0.709803922f, 0.898039216f, 1.0f };
    
    
    public Square() {
      
        int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
        int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);

        mProgram = GLES20.glCreateProgram();             // create empty OpenGL ES Program
        GLES20.glAttachShader(mProgram, vertexShader);   // add the vertex shader to program
        GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
        GLES20.glLinkProgram(mProgram);                  // creates OpenGL ES program executables
      
        // initialize vertex byte buffer for shape coordinates
        ByteBuffer bb = ByteBuffer.allocateDirect(
        // (# of coordinate values * 4 bytes per float)
                squareCoords.length * 4);
        bb.order(ByteOrder.nativeOrder());
        vertexBuffer = bb.asFloatBuffer();
        vertexBuffer.put(squareCoords);
        vertexBuffer.position(0);

        // initialize byte buffer for the draw list
        ByteBuffer dlb = ByteBuffer.allocateDirect(
        // (# of coordinate values * 2 bytes per short)
                drawOrder.length * 2);
        dlb.order(ByteOrder.nativeOrder());
        drawListBuffer = dlb.asShortBuffer();
        drawListBuffer.put(drawOrder);
        drawListBuffer.position(0);
    }
    

    public void draw(float[] mvpMatrix) {
        // Add program to OpenGL environment
        GLES20.glUseProgram(mProgram);

        // get handle to vertex shader's vPosition member
        mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");

        // Enable a handle to the triangle vertices
        GLES20.glEnableVertexAttribArray(mPositionHandle);

        // Prepare the triangle coordinate data
        GLES20.glVertexAttribPointer(
                mPositionHandle, COORDS_PER_VERTEX,
                GLES20.GL_FLOAT, false,
                vertexStride, vertexBuffer);

        // get handle to fragment shader's vColor member
        mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");

        // Set color for drawing the triangle
        GLES20.glUniform4fv(mColorHandle, 1, color, 0);

        // get handle to shape's transformation matrix
        mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
        MyGLRenderer.checkGlError("glGetUniformLocation");

        // Apply the projection and view transformation
        GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
        MyGLRenderer.checkGlError("glUniformMatrix4fv");

        // Draw the square
        GLES20.glDrawElements(
                GLES20.GL_TRIANGLES, drawOrder.length,
                GLES20.GL_UNSIGNED_SHORT, drawListBuffer);

        // Disable vertex array
        GLES20.glDisableVertexAttribArray(mPositionHandle);
    }
    
}

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