Android example source code file (StaticTriangleRenderer.java)

This example Android source code file (StaticTriangleRenderer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, bytebuffer, drawing, floatbuffer, gl_clamp_to_edge, gl_depth_buffer_bit, gl_float, gl_repeat, gl_texture_env_mode, gl_texture_wrap_s, gl_texture_wrap_t, graphics, io, nio, opengl, robottextureloader, statictrianglerenderer, textureloader, triangle, verts

The StaticTriangleRenderer.java Android example source code

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics;

import static android.opengl.GLES10.*;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLSurfaceView;
import android.opengl.GLU;
import android.opengl.GLUtils;
import android.os.SystemClock;

import com.example.android.apis.R;

/**
 * A GLSurfaceView.Renderer that uses the Android-specific
 * android.opengl.GLESXXX static OpenGL ES APIs. The static APIs
 * expose more of the OpenGL ES features than the
 * javax.microedition.khronos.opengles APIs, and also
 * provide a programming model that is closer to the C OpenGL ES APIs, which
 * may make it easier to reuse code and documentation written for the
 * C OpenGL ES APIs.
 *
 */
public class StaticTriangleRenderer implements GLSurfaceView.Renderer{

    public interface TextureLoader {
        /**
         * Load a texture into the currently bound OpenGL texture.
         */
        void load(GL10 gl);
    }

    public StaticTriangleRenderer(Context context) {
        init(context, new RobotTextureLoader());
    }

    public StaticTriangleRenderer(Context context, TextureLoader loader) {
        init(context, loader);
    }

    private void init(Context context, TextureLoader loader) {
        mContext = context;
        mTriangle = new Triangle();
        mTextureLoader = loader;
    }

    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        /*
         * By default, OpenGL enables features that improve quality
         * but reduce performance. One might want to tweak that
         * especially on software renderer.
         */
        glDisable(GL_DITHER);

        /*
         * Some one-time OpenGL initialization can be made here
         * probably based on features of this particular context
         */
        glHint(GL_PERSPECTIVE_CORRECTION_HINT,
                GL_FASTEST);

        glClearColor(.5f, .5f, .5f, 1);
        glShadeModel(GL_SMOOTH);
        glEnable(GL_DEPTH_TEST);
        glEnable(GL_TEXTURE_2D);

        /*
         * Create our texture. This has to be done each time the
         * surface is created.
         */

        int[] textures = new int[1];
        glGenTextures(1, textures, 0);

        mTextureID = textures[0];
        glBindTexture(GL_TEXTURE_2D, mTextureID);

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                GL_NEAREST);
        glTexParameterf(GL_TEXTURE_2D,
                GL_TEXTURE_MAG_FILTER,
                GL_LINEAR);

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
                GL_CLAMP_TO_EDGE);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
                GL_CLAMP_TO_EDGE);

        glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,
                GL_REPLACE);
        mTextureLoader.load(gl);
    }

    public void onDrawFrame(GL10 gl) {
        /*
         * By default, OpenGL enables features that improve quality
         * but reduce performance. One might want to tweak that
         * especially on software renderer.
         */
        glDisable(GL_DITHER);

        glTexEnvx(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,
                GL_MODULATE);

        /*
         * Usually, the first thing one might want to do is to clear
         * the screen. The most efficient way of doing this is to use
         * glClear().
         */

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        /*
         * Now we're ready to draw some 3D objects
         */

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        GLU.gluLookAt(gl, 0, 0, -5, 0f, 0f, 0f, 0f, 1.0f, 0.0f);

        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);

        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, mTextureID);
        glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
                GL_REPEAT);
        glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
                GL_REPEAT);

        long time = SystemClock.uptimeMillis() % 4000L;
        float angle = 0.090f * ((int) time);

        glRotatef(angle, 0, 0, 1.0f);

        mTriangle.draw(gl);
    }

    public void onSurfaceChanged(GL10 gl, int w, int h) {
        glViewport(0, 0, w, h);

        /*
        * Set our projection matrix. This doesn't have to be done
        * each time we draw, but usually a new projection needs to
        * be set when the viewport is resized.
        */

        float ratio = (float) w / h;
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glFrustumf(-ratio, ratio, -1, 1, 3, 7);
    }

    private Context mContext;
    private Triangle mTriangle;
    private int mTextureID;
    private TextureLoader mTextureLoader;

    private class RobotTextureLoader implements TextureLoader {
        public void load(GL10 gl) {
            InputStream is = mContext.getResources().openRawResource(
                    R.raw.robot);
            Bitmap bitmap;
            try {
                bitmap = BitmapFactory.decodeStream(is);
            } finally {
                try {
                    is.close();
                } catch (IOException e) {
                    // Ignore.
                }
            }

            GLUtils.texImage2D(GL_TEXTURE_2D, 0, bitmap, 0);
            bitmap.recycle();
        }
    }

    static class Triangle {
        public Triangle() {

            // Buffers to be passed to gl*Pointer() functions
            // must be direct, i.e., they must be placed on the
            // native heap where the garbage collector cannot
            // move them.
            //
            // Buffers with multi-byte datatypes (e.g., short, int, float)
            // must have their byte order set to native order

            ByteBuffer vbb = ByteBuffer.allocateDirect(VERTS * 3 * 4);
            vbb.order(ByteOrder.nativeOrder());
            mFVertexBuffer = vbb.asFloatBuffer();

            ByteBuffer tbb = ByteBuffer.allocateDirect(VERTS * 2 * 4);
            tbb.order(ByteOrder.nativeOrder());
            mTexBuffer = tbb.asFloatBuffer();

            ByteBuffer ibb = ByteBuffer.allocateDirect(VERTS * 2);
            ibb.order(ByteOrder.nativeOrder());
            mIndexBuffer = ibb.asShortBuffer();

            // A unit-sided equilateral triangle centered on the origin.
            float[] coords = {
                    // X, Y, Z
                    -0.5f, -0.25f, 0,
                     0.5f, -0.25f, 0,
                     0.0f,  0.559016994f, 0
            };

            for (int i = 0; i < VERTS; i++) {
                for(int j = 0; j < 3; j++) {
                    mFVertexBuffer.put(coords[i*3+j] * 2.0f);
                }
            }

            for (int i = 0; i < VERTS; i++) {
                for(int j = 0; j < 2; j++) {
                    mTexBuffer.put(coords[i*3+j] * 2.0f + 0.5f);
                }
            }

            for(int i = 0; i < VERTS; i++) {
                mIndexBuffer.put((short) i);
            }

            mFVertexBuffer.position(0);
            mTexBuffer.position(0);
            mIndexBuffer.position(0);
        }

        public void draw(GL10 gl) {
            glFrontFace(GL_CCW);
            glVertexPointer(3, GL_FLOAT, 0, mFVertexBuffer);
            glEnable(GL_TEXTURE_2D);
            glTexCoordPointer(2, GL_FLOAT, 0, mTexBuffer);
            glDrawElements(GL_TRIANGLE_STRIP, VERTS,
                    GL_UNSIGNED_SHORT, mIndexBuffer);
        }

        private final static int VERTS = 3;

        private FloatBuffer mFVertexBuffer;
        private FloatBuffer mTexBuffer;
        private ShortBuffer mIndexBuffer;
    }
}