0x0000 寫在前面
記得第一次做貪吃蛇，是在大一學習C++，在貼吧看到了源碼，心里一動，連抄帶蒙，用VS實現了出來。
晃眼間十年過去了，看到Google官方的demo，一時興起又寫了一遍。當時寫了一周的貪吃蛇，今天只寫了不到兩小時。那時候沒想到自己以后會當程序員吧。
0x0001 功能簡介
以下幾個功能點：
- 蛇在屏幕移動
- 蘋果隨機出現
- 根據Touch位置改變蛇的移動方向
- 游戲失敗條件
0x0002 程序源碼
MainActivity.java
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
ScreenUtils.init(getApplicationContext());
setContentView(R.layout.activity_main);
}
}
SnakeView.java
public class SnakeView extends View {
private final int DIRECTION_L = 0x1001;
private final int DIRECTION_T = 0x0011;
private final int DIRECTION_R = 0x0110;
private final int DIRECTION_B = 0x1100;
private final int CANVAS_REFRESH_INTERVAL = 300;
private final int APPLE_STROKE_WIDTH = 50;
private final int SNAKE_STROKE_WIDTH = 50;
private final int MOVE_DISTANCE = 50;
private final Paint applePaint = new Paint();
private final Paint snakePaint = new Paint();
private final Point apple = new Point();
private final List<Point> snakeBody = new ArrayList<>();
private int currDirection = DIRECTION_R;
private int lastDirection = currDirection;
private int hCount;
private int vCount;
private Random random = new Random();
private final Runnable refresh = new Runnable() {
@Override
public void run() {
updateSnake();
SnakeView.this.invalidate();
}
};
public SnakeView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public SnakeView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initBound();
initPaint();
initApple();
initSnake();
}
private void reset() {
initApple();
initSnake();
currDirection = DIRECTION_R;
lastDirection = DIRECTION_R;
}
private void initBound() {
int width = ScreenUtils.getScreenWidth(getContext());
int height = ScreenUtils.getScreenHeight(getContext());
hCount = width / MOVE_DISTANCE;
vCount = height / MOVE_DISTANCE;
}
private void initPaint() {
applePaint.setAntiAlias(true);
applePaint.setColor(Color.RED);
applePaint.setStyle(Paint.Style.FILL);
applePaint.setStrokeWidth(APPLE_STROKE_WIDTH);
snakePaint.setAntiAlias(true);
snakePaint.setColor(Color.WHITE);
snakePaint.setStyle(Paint.Style.FILL);
snakePaint.setStrokeWidth(SNAKE_STROKE_WIDTH);
}
private void initSnake() {
Point head = new Point(300, 500);
Point body = new Point(250, 500);
Point tail = new Point(200, 500);
snakeBody.clear();
snakeBody.add(head);
snakeBody.add(body);
snakeBody.add(tail);
}
private void initApple() {
apple.set(900, 200);
}
private void updateSnake() {
Point head = snakeBody.get(0);
Point temp = new Point(head);
switch (currDirection) {
case DIRECTION_L:
temp.x -= MOVE_DISTANCE;
break;
case DIRECTION_T:
temp.y -= MOVE_DISTANCE;
break;
case DIRECTION_R:
temp.x += MOVE_DISTANCE;
break;
case DIRECTION_B:
temp.y += MOVE_DISTANCE;
break;
default:
temp.x += MOVE_DISTANCE;
break;
}
if (snakeBody.contains(temp)) {
//蛇的頭部撞到了自己，GAME OVER!
Toast.makeText(getContext(), "GAME OVER!", Toast.LENGTH_LONG).show();
reset();
return;
}
if (temp.x < MOVE_DISTANCE * 2 || temp.x > MOVE_DISTANCE * hCount
|| temp.y < MOVE_DISTANCE * 2 || temp.y > MOVE_DISTANCE * vCount) {
//蛇的頭部撞到了墻，GAME OVER!
Toast.makeText(getContext(), "GAME OVER!", Toast.LENGTH_LONG).show();
reset();
return;
}
snakeBody.add(0, temp);
lastDirection = currDirection;
if (snakeBody.contains(apple)) {
updateApple();
} else {
snakeBody.remove(snakeBody.size() - 1);
}
}
private void updateApple() {
int x = (2 + random.nextInt(hCount)) * MOVE_DISTANCE;
int y = (2 + random.nextInt(vCount)) * MOVE_DISTANCE;
apple.set(x, y);
if (snakeBody.contains(apple)) {
updateApple();
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (Point point : snakeBody) {
canvas.drawPoint(point.x, point.y, snakePaint);
}
canvas.drawPoint(apple.x, apple.y, applePaint);
this.postDelayed(refresh, CANVAS_REFRESH_INTERVAL);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() != MotionEvent.ACTION_DOWN) {
return super.onTouchEvent(event);
}
float x = event.getX();
float y = event.getY();
int snakeX = snakeBody.get(0).x;
int snakeY = snakeBody.get(0).y;
if (Math.abs(x - snakeX) >= Math.abs(y - snakeY)) {
if (x > snakeX) {
currDirection = DIRECTION_R;
} else {
currDirection = DIRECTION_L;
}
} else {
if (y > snakeY) {
currDirection = DIRECTION_B;
} else {
currDirection = DIRECTION_T;
}
}
if ((currDirection & lastDirection) == 0) {
currDirection = lastDirection;
}
return super.onTouchEvent(event);
}
}
ScreenUtils.java
public class ScreenUtils {
private static int sScreenWidth;
private static int sScreenHeight;
public static void init(Context context) {
Resources resources = context.getResources();
DisplayMetrics dm = resources.getDisplayMetrics();
sScreenWidth = dm.widthPixels;
sScreenHeight = dm.heightPixels;
}
public static int getScreenWidth(Context context) {
if (sScreenWidth <= 0) {
init(context);
}
return sScreenWidth;
}
public static int getScreenHeight(Context context) {
if (sScreenHeight <= 0) {
init(context);
}
return sScreenHeight;
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent">
<custom.widget.SnakeView
android:id="@+id/snake"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/black" />
</RelativeLayout>
