Android中贪吃蛇游戏的学习（3）
Android中贪吃蛇游戏的学习（三）
视图VIew的类的Snake的，主要关注的学习的类。
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 + "]";
}
}
}