grid.java

android 例子中的确良ApiDemos。很有代表意义

/*
 * 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.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;
		mVertexArray = new float[size * 3];
		mVertexBuffer = FloatBuffer.wrap(mVertexArray);

		mTexCoordArray = new float[size * 2];
		mTexCoordBuffer = FloatBuffer.wrap(mTexCoordArray);

		int quadW = mW - 1;
		int quadH = mH - 1;
		int quadCount = quadW * quadH;
		int indexCount = quadCount * 6;
		mIndexCount = indexCount;
		char[] indexArray = new char[indexCount];

		/*
		 * 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);

					indexArray[i++] = a;
					indexArray[i++] = b;
					indexArray[i++] = c;

					indexArray[i++] = b;
					indexArray[i++] = c;
					indexArray[i++] = d;
				}
			}
		}

		mIndexBuffer = CharBuffer.wrap(indexArray);
	}

	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;
		mVertexArray[posIndex] = x;
		mVertexArray[posIndex + 1] = y;
		mVertexArray[posIndex + 2] = z;

		int texIndex = index * 2;
		mTexCoordArray[texIndex] = u;
		mTexCoordArray[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 float[] mVertexArray;

	private FloatBuffer mTexCoordBuffer;
	private float[] mTexCoordArray;

	private CharBuffer mIndexBuffer;

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