【贪吃蛇—Java程序员写Android游戏】系列 1.Android SDK

【贪吃蛇—Java程序员写Android游戏】系列 1.Android SDKSample-Snake详解分类：1.Android【贪吃蛇—Java程序员写Android游戏】2011-03-31 16:18 7307人阅读评论(13) 收藏举报Snake也是一个经典游戏了， Nokia蓝屏机的王牌游戏之一。

Android SDK 1.5就有了它的身影。

我们这里就来详细解析一下 Android SDK Sample中的 Snake工程。

本工程基于 SDK 2.3.3版本中的工程，路径为：%Android_SDK_HOME% /samples/android-10/Snake一、 Eclipse工程通过 File-New Project-Android-Android Project，选择“ Create project from existing sample”创建自己的应用 SnakeAndroid，如下图：运行效果如下图：二、工程结构和类图其实 Snake的工程蛮简单的，源文件就三个： Snake.java SnakeView.javaTileView.java。

Snake类是这个游戏的入口点， TitleView类进行游戏的绘画， SnakeView类则是对游戏控制操作的处理。

Coordinate，RefreshHandler是 2个辅助类，也是 SnakeView类中的内部类。

其中， Coordinate是一个点的坐标（ x， y），RefreshHandler将 RefreshHandler对象绑定某个线程并给它发送消息。

如下图：任何游戏都需要有个引擎来推动游戏的运行，最简化的游戏引擎就是：在一个线程中 While循环，检测用户操作，对用户的操作作出反应，更新游戏的界面，直到用户退出游戏。

在 Snake这个游戏中，辅助类 RefreshHandler继承自 Handler，用来把 RefreshHandler与当前线程进行绑定，从而可以直接给线程发送消息并处理消息。

注意一点： Handle对消息的处理都是异步。

RefreshHandler在Handler的基础上增加 sleep()接口，用来每隔一个时间段后给当前线程发送一个消息。

handleMessage()方法在接受消息后，根据当前的游戏状态重绘界面，运行机制如下：这比较类似定时器的概念，在特定的时刻发送消息，根据消息处理相应的事件。

update()与 sleep()间接的相互调用就构成了一个循环。

这里要注意： mRedrawHandle绑定的是 Avtivity所在的线程，也就是程序的主线程；另外由于 sleep()是个异步函数，所以 update()与 sleep()之间的相互调用才没有构成死循环。

最后分析下游戏数据的保存机制，如下：这里考虑了 Activity的生命周期：如果用户在游戏期间离开游戏界面，游戏暂停；或者由于内存比较紧张，Android关闭游戏释放内存，那么当用户返回游戏界面的时候恢复到上次离开时的界面。

三、源码解析详细解析下源代码，由于代码量不大，以注释的方式列出如下：1、 Snake.java[java]view plaincopy1./**2. * <p>Title: Snake</p>3. * <p>Copyright: (C) 2007 The Android Open Source Project. Licensed under the Apache License, Version 2.0 (the "License")</p>4. * @author Gavin 标注5. */6.package com.deaboway.snake;7.import android.app.Activity;8.import android.os.Bundle;9.import android.widget.TextView;10./**11. * Snake: a simple game that everyone can enjoy.12. *13. * This is an implementation of the classic Game "Snake", in which you control a14. * serpent roaming around the garden looking for apples. Be careful, though,15. * because when you catch one, not only will you become longer, but you'll move16. * faster. Running into yourself or the walls will end the game.17. *18. */19.// 贪吃蛇：经典游戏，在一个花园中找苹果吃，吃了苹果会变长，速度变快。

碰到自己和墙就挂掉。

20.public class Snake extends Activity {21.private SnakeView mSnakeView;22.private static String ICICLE_KEY = "snake-view";23./**24. * Called when Activity is first created. Turns off the title bar, sets up25. * the content views, and fires up the SnakeView.26. *27. */28.// 在 activity 第一次创建时被调用29.@Override30.public void onCreate(Bundle savedInstanceState) {31.super.onCreate(savedInstanceState);32. setContentView(yout.snake_layout);33. mSnakeView = (SnakeView) findViewById(R.id.snake);34. mSnakeView.setTextView((TextView) findViewById(R.id.text));35.// 检查存贮状态以确定是重新开始还是恢复状态36.if (savedInstanceState == null) {37.// 存储状态为空，说明刚启动可以切换到准备状态38. mSnakeView.setMode(SnakeView.READY);39. } else {40.// 已经保存过，那么就去恢复原有状态41. Bundle map = savedInstanceState.getBundle(ICICLE_KEY);42.if (map != null) {43.// 恢复状态44. mSnakeView.restoreState(map);45. } else {46.// 设置状态为暂停47. mSnakeView.setMode(SnakeView.PAUSE);48. }49. }50. }51.// 暂停事件被触发时52.@Override53.protected void onPause() {54.super.onPause();55.// Pause the game along with the activity56. mSnakeView.setMode(SnakeView.PAUSE);57. }58.// 状态保存59.@Override60.public void onSaveInstanceState(Bundle outState) {61.// 存储游戏状态到View里62. outState.putBundle(ICICLE_KEY, mSnakeView.saveState());63. }64.}2、 SnakeView.java[java]view plaincopy1./**2. * <p>Title: Snake</p>3. * <p>Copyright: (C) 2007 The Android Open Source Project. Licensed under the Apache License, Version 2.0 (the "License")</p>4. * @author Gavin 标注5. */6.package com.deaboway.snake;7.import java.util.ArrayList;8.import java.util.Random;9.import android.content.Context;10.import android.content.res.Resources;11.import android.os.Handler;12.import android.os.Message;13.import android.util.AttributeSet;14.import android.os.Bundle;15.import android.util.Log;16.import android.view.KeyEvent;17.import android.view.View;18.import android.widget.TextView;19./**20. * SnakeView: implementation of a simple game of Snake21. *22. *23. */24.public class SnakeView extends TileView {25.private static final String TAG = "Deaboway";26./**27. * Current mode of application: READY to run, RUNNING, or you have already28. * lost. static final ints are used instead of an enum for performance29. * reasons.30. */31.// 游戏状态，默认值是准备状态32.private int mMode = READY;33.// 游戏的四个状态暂停准备运行和失败34.public static final int PAUSE = 0;35.public static final int READY = 1;36.public static final int RUNNING = 2;37.public static final int LOSE = 3;38.// 游戏中蛇的前进方向，默认值北方39.private int mDirection = NORTH;40.// 下一步的移动方向，默认值北方41.private int mNextDirection = NORTH;42.// 游戏方向设定北南东西43.private static final int NORTH = 1;44.private static final int SOUTH = 2;45.private static final int EAST = 3;46.private static final int WEST = 4;47./**48. * Labels for the drawables that will be loaded into the TileView class49. */50.// 三种游戏元51.private static final int RED_STAR = 1;52.private static final int YELLOW_STAR = 2;53.private static final int GREEN_STAR = 3;54./**55. * mScore: used to track the number of apples captured mMoveDelay: number of56. * milliseconds between snake movements. This will decrease as apples are57. * captured.58. */59.// 游戏得分60.private long mScore = 0;61.// 移动延迟62.private long mMoveDelay = 600;63./**64. * mLastMove: tracks the absolute time when the snake last moved, and is65. * used to determine if a move should be made based on mMoveDelay.66. */67.// 最后一次移动时的毫秒时刻68.private long mLastMove;69./**70. * mStatusText: text shows to the user in some run states72.// 显示游戏状态的文本组件73.private TextView mStatusText;74./**75. * mSnakeTrail: a list of Coordinates that make up the snake's body76. * mAppleList: the secret location of the juicy apples the snake craves.77. */78.// 蛇身数组(数组以坐标对象为元素)79.private ArrayList<Coordinate> mSnakeTrail = new ArrayList<Coordinate>();80.// 苹果数组(数组以坐标对象为元素)81.private ArrayList<Coordinate> mAppleList = new ArrayList<Coordinate>();82./**83. * Everyone needs a little randomness in their life84. */85.// 随机数86.private static final Random RNG = new Random();87./**88. * Create a simple handler that we can use to cause animation to happen. We89. * set ourselves as a target and we can use the sleep() function to cause an90. * update/invalidate to occur at a later date.91. */92.// 创建一个Refresh Handler来产生动画：通过sleep()来实现93.private RefreshHandler mRedrawHandler = new RefreshHandler();94.// 一个Handler95.class RefreshHandler extends Handler {96.// 处理消息队列97.@Override98.public void handleMessage(Message msg) {99.// 更新View对象100. SnakeView.this.update();101.// 强制重绘102. SnakeView.this.invalidate();103. }104.// 延迟发送消息105.public void sleep(long delayMillis) {106.this.removeMessages(0);107. sendMessageDelayed(obtainMessage(0), delayMillis);108. }109. };110./**111. * Constructs a SnakeView based on inflation from XML112. *113. * @param context114. * @param attrs116.// 构造函数117.public SnakeView(Context context, AttributeSet attrs) {118.super(context, attrs);119.// 构造时初始化120. initSnakeView();121. }122.public SnakeView(Context context, AttributeSet attrs, int defStyle) { 123.super(context, attrs, defStyle);124. initSnakeView();125. }126.// 初始化127.private void initSnakeView() {128.// 可选焦点129. setFocusable(true);130. Resources r = this.getContext().getResources();131.// 设置贴片图片数组132. resetTiles(4);133.// 把三种图片存到Bitmap对象数组134. loadTile(RED_STAR, r.getDrawable(R.drawable.redstar));135. loadTile(YELLOW_STAR, r.getDrawable(R.drawable.yellowstar));136. loadTile(GREEN_STAR, r.getDrawable(R.drawable.greenstar));137. }138.// 开始新的游戏——初始化139.private void initNewGame() {140.// 清空ArrayList列表141. mSnakeTrail.clear();142. mAppleList.clear();143.// For now we're just going to load up a short default eastbound snake 144.// that's just turned north145.// 创建蛇身146. mSnakeTrail.add(new Coordinate(7, 7));147. mSnakeTrail.add(new Coordinate(6, 7));148. mSnakeTrail.add(new Coordinate(5, 7));149. mSnakeTrail.add(new Coordinate(4, 7));150. mSnakeTrail.add(new Coordinate(3, 7));151. mSnakeTrail.add(new Coordinate(2, 7));152.// 新的方向：北方153. mNextDirection = NORTH;154.// 2个随机位置的苹果155. addRandomApple();156. addRandomApple();157.// 移动延迟158. mMoveDelay = 600;159.// 初始得分0160. mScore = 0;161. }3、 TileView.java[java]view plaincopy1./**2. * <p>Title: Snake</p>3. * <p>Copyright: (C) 2007 The Android Open Source Project. Licensed under the Apache License, Version 2.0 (the "License")</p>4. * @author Gavin 标注5. */6.package com.deaboway.snake;7.import android.content.Context;8.import android.content.res.TypedArray;9.import android.graphics.Bitmap;10.import android.graphics.Canvas;11.import android.graphics.Paint;12.import android.graphics.drawable.Drawable;13.import android.util.AttributeSet;14.import android.view.View;15./**16. * TileView: a View-variant designed for handling arrays of "icons" or other17. * drawables.18. *19. */20.// View 变种，用来处理一组贴片——“icons”或其它可绘制的对象21.public class TileView extends View {22./**23. * Parameters controlling the size of the tiles and their range within view.24. * Width/Height are in pixels, and Drawables will be scaled to fit to these25. * dimensions. X/Y Tile Counts are the number of tiles that will be drawn.26. */27.protected static int mTileSize;28.// X轴的贴片数量29.protected static int mXTileCount;30.// Y轴的贴片数量31.protected static int mYTileCount;32.// X偏移量33.private static int mXOffset;34.// Y偏移量35.private static int mYOffset;36./**37. * A hash that maps integer handles specified by the subclasser to the38. * drawable that will be used for that reference39. */40.// 贴片图像的图像数组41.private Bitmap[] mTileArray;42./**43. * A two-dimensional array of integers in which the number represents the44. * index of the tile that should be drawn at that locations45. */46.// 保存每个贴片的索引——二维数组47.private int[][] mTileGrid;48.// Paint对象（画笔、颜料）49.private final Paint mPaint = new Paint();50.// 构造函数51.public TileView(Context context, AttributeSet attrs, int defStyle) {52.super(context, attrs, defStyle);53. TypedArray a = context.obtainStyledAttributes(attrs,54. R.styleable.TileView);55. mTileSize = a.getInt(R.styleable.TileView_tileSize, 12);56. a.recycle();57. }58.public TileView(Context context, AttributeSet attrs) {59.super(context, attrs);60. TypedArray a = context.obtainStyledAttributes(attrs,61. R.styleable.TileView);62. mTileSize = a.getInt(R.styleable.TileView_tileSize, 12);63. a.recycle();64. }65./**66. * Rests the internal array of Bitmaps used for drawing tiles, and sets the67. * maximum index of tiles to be inserted68. *69. * @param tilecount70. */71.// 设置贴片图片数组72.public void resetTiles(int tilecount) {73. mTileArray = new Bitmap[tilecount];74. }75.// 回调：当该View的尺寸改变时调用，在onDraw()方法调用之前就会被调用，所以用来设置一些变量的初始值76.// 在视图大小改变的时候调用，比如说手机由垂直旋转为水平77.@Override78.protected void onSizeChanged(int w, int h, int oldw, int oldh) {79.// 定义X轴贴片数量80. mXTileCount = (int) Math.floor(w / mTileSize);81. mYTileCount = (int) Math.floor(h / mTileSize);82.// X轴偏移量83. mXOffset = ((w - (mTileSize * mXTileCount)) / 2);84.// Y轴偏移量85. mYOffset = ((h - (mTileSize * mYTileCount)) / 2);86.// 定义贴片的二维数组87. mTileGrid = new int[mXTileCount][mYTileCount];88.// 清空所有贴片89. clearTiles();90. }91./**92. * Function to set the specified Drawable as the tile for a particular93. * integer key.94. *95. * @param key96. * @param tile97. */98.// 给mTileArray这个Bitmap图片数组设置值99.public void loadTile(int key, Drawable tile) {100. Bitmap bitmap = Bitmap.createBitmap(mTileSize, mTileSize,101. Bitmap.Config.ARGB_8888);102. Canvas canvas = new Canvas(bitmap);103. tile.setBounds(0, 0, mTileSize, mTileSize);104.// 把一个drawable转成一个Bitmap105. tile.draw(canvas);106.// 在数组里存入该Bitmap107. mTileArray[key] = bitmap;108. }109./**110. * Resets all tiles to 0 (empty)111. *112. */113.// 清空所有贴片114.public void clearTiles() {115.for (int x = 0; x < mXTileCount; x++) {116.for (int y = 0; y < mYTileCount; y++) {117.// 全部设置为0118. setTile(0, x, y);119. }120. }121. }122./**123. * Used to indicate that a particular tile (set with loadTile and referenced124. * by an integer) should be drawn at the given x/y coordinates during the125. * next invalidate/draw cycle.126. *127. * @param tileindex128. * @param x129. * @param y130. */131.// 给某个贴片位置设置一个状态索引132.public void setTile(int tileindex, int x, int y) {133. mTileGrid[x][y] = tileindex;134. }135.// onDraw 在视图需要重画的时候调用，比如说使用invalidate刷新界面上的某个矩形区域136.@Override137.public void onDraw(Canvas canvas) {138.super.onDraw(canvas);139.for (int x = 0; x < mXTileCount; x += 1) {140.for (int y = 0; y < mYTileCount; y += 1) {141.// 当索引大于零，也就是不空时142.if (mTileGrid[x][y] > 0) {143.// mTileGrid中不为零时画此贴片144. canvas.drawBitmap(mTileArray[mTileGrid[x][y]], mXOffset + x 145. * mTileSize, mYOffset + y * mTileSize, mPaint);146. }147. }148. }149. }150.}四、工程文件下载为了方便大家阅读，可以到如下地址下载工程源代码：/source/3145349五、小结及下期预告：本次详细解析了 Android SDK 自带 Sample—— Snake的结构和功能。