文章分类:移动开发
视图VIew的类的Snake的，主要关注的学习的类。
Java代码 package com.easyway.dev.android.snake; import java.util.ArrayList; import java.util.Random; import android.content.Context; import android.content.res.Resources; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.AttributeSet; import android.util.Log; import android.view.KeyEvent; import android.view.View; import android.widget.TextView; /** * View类是Android的一个超类，这个类几乎包含了所有的屏幕类型。但它们之间有一些不同。每一个view * 都有一个用于绘画的画布。这个画布可以用来进行任意扩展。 * * 一个项目的R.java文件是一个定义所有资源的索引文件。 使用这个类就像使用一种速记方式来引用你项 * 目中包含的资源。这个有点特别的强大像对于Eclipse这类IDE的代码编译特性，因为它使你快速的，互动 * 式的定位你正在寻找的特定引用。 * * 到目前需要注意的重要事情是叫做”layout”的内部类和他的成员变量”main”, 插件会通知你添加一个新 * 的XML布局文件，然后从新产生这个R.java文件，比如你添加了新的资源到你的项目，你将会看到R.java * 也相应的改变了。放在你的项目目录的res/ 文件夹下。 “res”是”resources”的缩写，它是存放所有非 * 代码资源的文件夹，包含象图片，本地化字符串和XML布局文件。 * * * SnakeView: implementation of a simple game of Snake * 创建的view中一般要传入一个Context的实例，Context 可以控制系统的调用，它提供了诸如资源解析 * ，访问数据库等。Activty类继承自Context类。 * * 视图也可以被嵌套，但和J2ME不同，我们可以将定制的视图和Android团队发布的Widgets一起使用。 * 在J2ME中，开发人员被迫选择GameCanvas和J2ME应用程序画布。这就意味着如果我们想要一个定制 * 的效果，就必须在GameCanvas上重新设计我们所有的widget。Android还不仅仅是这些，视图类型 * 也可以混合使用。Android还带了一个widget库，这个类库包括了滚动条，文本实体，进度条以及其 * 他很多控件。这些标准的widget可以被重载或被按着我们的习惯定制。 * */ public class SnakeView extends TileView { private static final String TAG = "SnakeView"; /** * Current mode of application: READY to run, RUNNING, or you have already * lost. static final ints are used instead of an enum for performance * reasons. */ private int mMode = READY; public static final int PAUSE = 0; public static final int READY = 1; public static final int RUNNING = 2; public static final int LOSE = 3; /** * 设置方向 * Current direction the snake is headed. */ private int mDirection = NORTH; private int mNextDirection = NORTH; private static final int NORTH = 1; private static final int SOUTH = 2; private static final int EAST = 3; private static final int WEST = 4; /** * Labels for the drawables that will be loaded into the TileView class */ private static final int RED_STAR = 1; private static final int YELLOW_STAR = 2; private static final int GREEN_STAR = 3; /** * mScore: used to track the number of apples captured mMoveDelay: number of * milliseconds between snake movements. This will decrease as apples are * captured. */ private long mScore = 0; private long mMoveDelay = 600; /** * mLastMove: tracks the absolute time when the snake last moved, and is used * to determine if a move should be made based on mMoveDelay. */ private long mLastMove; /** * mStatusText: text shows to the user in some run states */ private TextView mStatusText; /** * 用于存储贪吃蛇中，苹果和蛇的点阵的坐标的信息的集合 * mSnakeTrail: a list of Coordinates that make up the snake's body * mAppleList: the secret location of the juicy apples the snake craves. */ private ArrayList<Coordinate> mSnakeTrail = new ArrayList<Coordinate>(); private ArrayList<Coordinate> mAppleList = new ArrayList<Coordinate>(); /** * 为创建苹果坐标使用随机对象 * Everyone needs a little randomness in their life */ private static final Random RNG = new Random(); /** * 刷新界面处理器 * Create a simple handler that we can use to cause animation to happen. We * set ourselves as a target and we can use the sleep() * function to cause an update/invalidate to occur at a later date. */ private RefreshHandler mRedrawHandler = new RefreshHandler(); /** * 实现刷新的功能： *在J2ME中，刷新都是在canvas中通过调用线程结合repaint()来刷新， 他们使线程不断去循环， *去调用canvas, 笔者在android 入门时也曾经想用J2ME的模式用在android 中，结果报异常了， *为什么呢？ 很多人认为Dalvik虚拟机是一个Java虚拟机，因为Android的编程语言恰恰就是Java语言。 *但是这种说法并不准确，因为Dalvik虚拟机并不是按照Java虚拟机的规范来实现的，两者并不兼容； *同时还要两个明显的不同： Java虚拟机运行的是Java字节码，而Dalvik虚拟机运行的则是其专有的 *文件格式DEX（Dalvik Executable）。所以在以前JAVA 里面能使用的模式， 可能在android *里面用不起来 。在自带的例子里面他是通过消息的机制来刷新的。而在android的消定义比较广泛， * 比如，手机的暂停， 启动， 来电话、短信，键盘按下，弹起都是一个消息。总的来说， 事件就是消息； * 只要继承Handler类就可以对消息进行控制，或者处理， 根据具体情况进行具体处理： * * @author Administrator * @date 2010-5-24 * @version 1.0 * @since JDK6.0 */ class RefreshHandler extends Handler { /** * 响应消息 */ @Override public void handleMessage(Message msg) { SnakeView.this.update(); SnakeView.this.invalidate(); } /** * 向外提供人工的调用消息的接口 * @param delayMillis */ public void sleep(long delayMillis) { //注销消息 this.removeMessages(0); //添加消息 sendMessageDelayed(obtainMessage(0), delayMillis); } }; /** * Constructs a SnakeView based on inflation from XML * * @param context * @param attrs */ public SnakeView(Context context, AttributeSet attrs) { super(context, attrs); initSnakeView(); } public SnakeView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initSnakeView(); } /** * 初始化界面的 */ private void initSnakeView() { setFocusable(true); Resources r = this.getContext().getResources(); resetTiles(4); loadTile(RED_STAR, r.getDrawable(R.drawable.redstar)); loadTile(YELLOW_STAR, r.getDrawable(R.drawable.yellowstar)); loadTile(GREEN_STAR, r.getDrawable(R.drawable.greenstar)); } /** * 初始化新的游戏 */ private void initNewGame() { mSnakeTrail.clear(); mAppleList.clear(); // For now we're just going to load up a short default eastbound snake // that's just turned north //设置初始化蛇的位置 mSnakeTrail.add(new Coordinate(7, 7)); mSnakeTrail.add(new Coordinate(6, 7)); mSnakeTrail.add(new Coordinate(5, 7)); mSnakeTrail.add(new Coordinate(4, 7)); mSnakeTrail.add(new Coordinate(3, 7)); mSnakeTrail.add(new Coordinate(2, 7)); mNextDirection = NORTH; // Two apples to start with //设置苹果的位置 addRandomApple(); addRandomApple(); // mMoveDelay = 600; //设置积分的 mScore = 0; } /** * Given a ArrayList of coordinates, we need to flatten them into an array of * ints before we can stuff them into a map for flattening and storage. * * @param cvec : a ArrayList of Coordinate objects * @return : a simple array containing the x/y values of the coordinates * as [x1,y1,x2,y2,x3,y3...] */ private int[] coordArrayListToArray(ArrayList<Coordinate> cvec) { int count = cvec.size(); int[] rawArray = new int[count * 2]; for (int index = 0; index < count; index++) { Coordinate c = cvec.get(index); rawArray[2 * index] = c.x; rawArray[2 * index + 1] = c.y; } return rawArray; } /** * Save game state so that the user does not lose anything * if the game process is killed while we are in the * background. * * @return a Bundle with this view's state */ public Bundle saveState() { Bundle map = new Bundle(); map.putIntArray("mAppleList", coordArrayListToArray(mAppleList)); map.putInt("mDirection", Integer.valueOf(mDirection)); map.putInt("mNextDirection", Integer.valueOf(mNextDirection)); map.putLong("mMoveDelay", Long.valueOf(mMoveDelay)); map.putLong("mScore", Long.valueOf(mScore)); map.putIntArray("mSnakeTrail", coordArrayListToArray(mSnakeTrail)); return map; } /** * Given a flattened array of ordinate pairs, we reconstitute them into a * ArrayList of Coordinate objects * * @param rawArray : [x1,y1,x2,y2,...] * @return a ArrayList of Coordinates */ private ArrayList<Coordinate> coordArrayToArrayList(int[] rawArray) { ArrayList<Coordinate> coordArrayList = new ArrayList<Coordinate>(); int coordCount = rawArray.length; for (int index = 0; index < coordCount; index += 2) { Coordinate c = new Coordinate(rawArray[index], rawArray[index + 1]); coordArrayList.add(c); } return coordArrayList; } /** * Restore game state if our process is being relaunched * * @param icicle a Bundle containing the game state */ public void restoreState(Bundle icicle) { setMode(PAUSE); //从资源中获取ArrayList mAppleList = coordArrayToArrayList(icicle.getIntArray("mAppleList")); mDirection = icicle.getInt("mDirection"); mNextDirection = icicle.getInt("mNextDirection"); mMoveDelay = icicle.getLong("mMoveDelay"); mScore = icicle.getLong("mScore"); mSnakeTrail = coordArrayToArrayList(icicle.getIntArray("mSnakeTrail")); } /** * 重点的控制代码 * * 实现键盘事件： 键盘主要起操作作用， 在任何的手机游戏中键盘都是起重要的用，要本游戏中， * 他就是起控制蛇的行走方向： 现在我们分析他的代码： * 就是通过判断那个键按下， 然后再给要走的方向（mDirection）赋值。 * * handles key events in the game. Update the direction our snake is traveling * based on the DPAD. Ignore events that would cause the snake to immediately * turn back on itself. * * (non-Javadoc) * * @see android.view.View#onKeyDown(int, android.os.KeyEvent) */ @Override public boolean onKeyDown(int keyCode, KeyEvent msg) { if (keyCode == KeyEvent.KEYCODE_DPAD_UP) { if (mMode == READY | mMode == LOSE) { /* * At the beginning of the game, or the end of a previous one, * we should start a new game. */ initNewGame(); setMode(RUNNING); update(); return (true); } if (mMode == PAUSE) { /* * If the game is merely paused, we should just continue where * we left off. */ setMode(RUNNING); update(); return (true); } if (mDirection != SOUTH) { mNextDirection = NORTH; } return (true); } if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN) { if (mDirection != NORTH) { mNextDirection = SOUTH; } return (true); } if (keyCode == KeyEvent.KEYCODE_DPAD_LEFT) { if (mDirection != EAST) { mNextDirection = WEST; } return (true); } if (keyCode == KeyEvent.KEYCODE_DPAD_RIGHT) { if (mDirection != WEST) { mNextDirection = EAST; } return (true); } return super.onKeyDown(keyCode, msg); } /** * Sets the TextView that will be used to give information (such as "Game * Over" to the user. * * @param newView */ public void setTextView(TextView newView) { mStatusText = newView; } /** * Updates the current mode of the application (RUNNING or PAUSED or the like) * as well as sets the visibility of textview for notification * * @param newMode */ public void setMode(int newMode) { int oldMode = mMode; mMode = newMode; if (newMode == RUNNING & oldMode != RUNNING) { mStatusText.setVisibility(View.INVISIBLE); update(); return; } Resources res = getContext().getResources(); CharSequence str = ""; if (newMode == PAUSE) { str = res.getText(R.string.mode_pause); } if (newMode == READY) { str = res.getText(R.string.mode_ready); } if (newMode == LOSE) { str = res.getString(R.string.mode_lose_prefix) + mScore + res.getString(R.string.mode_lose_suffix); } mStatusText.setText(str); mStatusText.setVisibility(View.VISIBLE); } /** * * 生成苹果位置的代码： * 苹果的位置就是更简单了，他是随机生成的， 而且必须在现在蛇的位置相对远距离。 * * Selects a random location within the garden that is not currently covered * by the snake. Currently _could_ go into an infinite loop if the snake * currently fills the garden, but we'll leave discovery of this prize to a * truly excellent snake-player. * */ private void addRandomApple() { Coordinate newCoord = null; boolean found = false; while (!found) { //随机生成新的X，Y位置 // Choose a new location for our apple int newX = 1 + RNG.nextInt(mXTileCount - 2); int newY = 1 + RNG.nextInt(mYTileCount - 2); newCoord = new Coordinate(newX, newY); // Make sure it's not already under the snake boolean collision = false; int snakelength = mSnakeTrail.size(); for (int index = 0; index < snakelength; index++) { //检查一下存放的位置是否合理 if (mSnakeTrail.get(index).equals(newCoord)) { collision = true; } } // if we're here and there's been no collision, then we have // a good location for an apple. Otherwise, we'll circle back // and try again found = !collision; } if (newCoord == null) { Log.e(TAG, "Somehow ended up with a null newCoord!"); } //添加苹果的列表中的 mAppleList.add(newCoord); } /** * Handles the basic update loop, checking to see if we are in the running * state, determining if a move should be made, updating the snake's location. */ public void update() { if (mMode == RUNNING) { long now = System.currentTimeMillis(); if (now - mLastMove > mMoveDelay) { clearTiles(); updateWalls(); updateSnake(); updateApples(); mLastMove = now; } mRedrawHandler.sleep(mMoveDelay); } } /** * 调用以上的方法以循环的方式位置数组赋值以及图片的索引。 * * Draws some walls. * */ private void updateWalls() { for (int x = 0; x < mXTileCount; x++) { setTile(GREEN_STAR, x, 0); //设置顶部的界限的位置 setTile(GREEN_STAR, x, mYTileCount - 1); //设置底部界限的位置 } for (int y = 1; y < mYTileCount - 1; y++) { setTile(GREEN_STAR, 0, y); //设置顶部的界限的位置 setTile(GREEN_STAR, mXTileCount - 1, y); //设置底部界限的位置 } } /** * Draws some apples. * */ private void updateApples() { for (Coordinate c : mAppleList) { setTile(YELLOW_STAR, c.x, c.y); } } /** * 设置当前蛇的方向位置： * 从以上的键盘代码我们可以看得出，程序中是通过触发来改变坐标（+1，-1）的方式来改蛇头的方向， * 可见坐标在游戏编程中的作用， 这个也是根据手机的屏幕是点阵的方式来显示， 所以坐标就是一个 * 定位器。 在这里大家可能还有一个疑问。 就是就这个蛇什么能够以“7”字形来移动行走， 其实我们 * 稍微仔细观察一下就知道了，在这里面， 他们也是通过坐标的传递来实现的， 只要把头部的坐标点 * 依次赋给下一个点， 后面的每一个点都走过了头部所走过的点，而蛇的头部就是负责去获取坐标，整 * 个蛇的行走起来就很自然和连贯。 坐标的方向变换又是通过判断那个方向按键的按下来改变的， 这 * 样一来， 键盘的作用就发挥出来了。蛇吃苹果又是怎样去实现？上面我所说到的坐标就起了作用。在蛇 * 所经过的每一个坐标， 他们都要在苹果所在的（ArrayList<Coordinate> mAppleList = new * ArrayList<Coordinate>()）坐标集里面集依次判断，若是坐标相同，那个这个苹果就被蛇吃了 。 * * Figure out which way the snake is going, see if he's run into anything (the * walls, himself, or an apple). If he's not going to die, we then add to the * front and subtract from the rear in order to simulate motion. If we want to * grow him, we don't subtract from the rear. * */ private void updateSnake() { boolean growSnake = false; // grab the snake by the head //获取蛇的头部 Coordinate head = mSnakeTrail.get(0); //创建一个新的蛇的头部应该的位置 Coordinate newHead = new Coordinate(1, 1); //根据当前的为方向设置坐标的信息 mDirection = mNextDirection; switch (mDirection) { case EAST: { newHead = new Coordinate(head.x + 1, head.y); break; } case WEST: { newHead = new Coordinate(head.x - 1, head.y); break; } case NORTH: { newHead = new Coordinate(head.x, head.y - 1); break; } case SOUTH: { newHead = new Coordinate(head.x, head.y + 1); break; } } // Collision detection // For now we have a 1-square wall around the entire arena if ((newHead.x < 1) || (newHead.y < 1) || (newHead.x > mXTileCount - 2) || (newHead.y > mYTileCount - 2)) { setMode(LOSE); return; } // Look for collisions with itself int snakelength = mSnakeTrail.size(); for (int snakeindex = 0; snakeindex < snakelength; snakeindex++) { Coordinate c = mSnakeTrail.get(snakeindex); if (c.equals(newHead)) { setMode(LOSE); return; } } // Look for apples //查找苹果设置苹果新的位置的信息 int applecount = mAppleList.size(); for (int appleindex = 0; appleindex < applecount; appleindex++) { Coordinate c = mAppleList.get(appleindex); if (c.equals(newHead)) { mAppleList.remove(c); addRandomApple(); mScore++; //设置的移动的速度 mMoveDelay *= 0.9; growSnake = true; } } //将蛇头的位置信息放在第一个的对象中方取值 // push a new head onto the ArrayList and pull off the tail mSnakeTrail.add(0, newHead); // except if we want the snake to grow if (!growSnake) { mSnakeTrail.remove(mSnakeTrail.size() - 1); } int index = 0; for (Coordinate c : mSnakeTrail) { if (index == 0) { setTile(YELLOW_STAR, c.x, c.y); } else { setTile(RED_STAR, c.x, c.y); } index++; } } /** * 用于存储每一个位点的x，y坐标信息 * Simple class containing two integer values and a comparison function. * There's probably something I should use instead, but this was quick and * easy to build. * */ private class Coordinate { public int x; public int y; public Coordinate(int newX, int newY) { x = newX; y = newY; } public boolean equals(Coordinate other) { if (x == other.x && y == other.y) { return true; } return false; } @Override public String toString() { return "Coordinate: [" + x + "," + y + "]"; } } }