Android example source code file (Grid.java)

This example Android source code file (Grid.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

char_size, charbuffer, float_size, floatbuffer, grid, illegalargumentexception, io, nio

The Grid.java Android example source code

/*
 * Copyright (C) 2007 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.spritetext;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
import java.nio.FloatBuffer;

import javax.microedition.khronos.opengles.GL10;

/**
 * A 2D rectangular mesh. Can be drawn textured or untextured.
 *
 */
class Grid {

    public Grid(int w, int h) {
        if (w < 0 || w >= 65536) {
            throw new IllegalArgumentException("w");
        }
        if (h < 0 || h >= 65536) {
            throw new IllegalArgumentException("h");
        }
        if (w * h >= 65536) {
            throw new IllegalArgumentException("w * h >= 65536");
        }

        mW = w;
        mH = h;
        int size = w * h;
        final int FLOAT_SIZE = 4;
        final int CHAR_SIZE = 2;
        mVertexBuffer = ByteBuffer.allocateDirect(FLOAT_SIZE * size * 3)
            .order(ByteOrder.nativeOrder()).asFloatBuffer();
        mTexCoordBuffer = ByteBuffer.allocateDirect(FLOAT_SIZE * size * 2)
            .order(ByteOrder.nativeOrder()).asFloatBuffer();

        int quadW = mW - 1;
        int quadH = mH - 1;
        int quadCount = quadW * quadH;
        int indexCount = quadCount * 6;
        mIndexCount = indexCount;
        mIndexBuffer = ByteBuffer.allocateDirect(CHAR_SIZE * indexCount)
            .order(ByteOrder.nativeOrder()).asCharBuffer();

        /*
         * Initialize triangle list mesh.
         *
         *     [0]-----[  1] ...
         *      |    /   |
         *      |   /    |
         *      |  /     |
         *     [w]-----[w+1] ...
         *      |       |
         *
         */

        {
            int i = 0;
            for (int y = 0; y < quadH; y++) {
                for (int x = 0; x < quadW; x++) {
                    char a = (char) (y * mW + x);
                    char b = (char) (y * mW + x + 1);
                    char c = (char) ((y + 1) * mW + x);
                    char d = (char) ((y + 1) * mW + x + 1);

                    mIndexBuffer.put(i++, a);
                    mIndexBuffer.put(i++, b);
                    mIndexBuffer.put(i++, c);

                    mIndexBuffer.put(i++, b);
                    mIndexBuffer.put(i++, c);
                    mIndexBuffer.put(i++, d);
                }
            }
        }

    }

    void set(int i, int j, float x, float y, float z, float u, float v) {
        if (i < 0 || i >= mW) {
            throw new IllegalArgumentException("i");
        }
        if (j < 0 || j >= mH) {
            throw new IllegalArgumentException("j");
        }

        int index = mW * j + i;

        int posIndex = index * 3;
        mVertexBuffer.put(posIndex, x);
        mVertexBuffer.put(posIndex + 1, y);
        mVertexBuffer.put(posIndex + 2, z);

        int texIndex = index * 2;
        mTexCoordBuffer.put(texIndex, u);
        mTexCoordBuffer.put(texIndex + 1, v);
    }

    public void draw(GL10 gl, boolean useTexture) {
        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVertexBuffer);

        if (useTexture) {
            gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
            gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, mTexCoordBuffer);
            gl.glEnable(GL10.GL_TEXTURE_2D);
        } else {
            gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
            gl.glDisable(GL10.GL_TEXTURE_2D);
        }

        gl.glDrawElements(GL10.GL_TRIANGLES, mIndexCount,
                GL10.GL_UNSIGNED_SHORT, mIndexBuffer);
        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
    }

    private FloatBuffer mVertexBuffer;
    private FloatBuffer mTexCoordBuffer;
    private CharBuffer mIndexBuffer;

    private int mW;
    private int mH;
    private int mIndexCount;
}