如何使用 SFML 在蛇游戏中定义游戏？

Question

so recently I have been wanting to make a snake game in C++ using SFML in Microsoft Visual studio 2015 and I made one and I am actually pretty satisfied with my work but there is a problem, that I forgot to make a game over for it and it seems like I couldn't make it work and it really had me on edge. So I thought I could use stack overflow's help. I would really appreciate it if you guys would let me know how to make it work and please keep it simple obvious. Here is my code:

// GraphicalLoopSnakeGame.cpp : Defines the entry point for the console application.

#include "stdafx.h"
#include <ctime>
#include <SFML/Graphics.hpp>

using namespace sf;

int N = 30, M = 20;
int size = 16;
int w = size * N;
int h = size * M;

int dir, num = 4;

struct Snake {
    int x, y;
} s[100];

struct Fruit {
    int x, y;
} f;

void Tick() {
    for(int i = num; i > 0; --i) {
        s[i].x = s[i - 1].x;
        s[i].y = s[i - 1].y;
    }

    if(dir == 0) s[0].y += 1;
    if(dir == 1) s[0].x -= 1;
    if(dir == 2) s[0].x += 1;
    if(dir == 3) s[0].y -= 1;

    if((s[0].x == f.x) && (s[0].y == f.y)) {
        num++;
        f.x = rand() % N;
        f.y = rand() % M;
    }

    if(s[0].x > N) s[0].x = 0;
    if(s[0].x < 0) s[0].x = N;
    if(s[0].y > M) s[0].y = 0;
    if(s[0].y < 0) s[0].y = M;

    for(int i = 1; i < num; i++)
        if(s[0].x == s[i].x && s[0].y == s[i].y) num = i;
}

int main() {
    srand(time(0));
    RenderWindow window(VideoMode(w, h), "Snake Game!");

    Texture t1, t2, t3;

    t1.loadFromFile("images/white.png");
    t2.loadFromFile("images/red.png");
    t3.loadFromFile("images/green.png");

    Sprite sprite1(t1);
    Sprite sprite2(t2);
    Sprite sprite3(t3);

    Clock clock;
    float timer = 0, delay = 0.13;

    f.x = 10;
    f.y = 10;

    while(window.isOpen()) {
        float time = clock.getElapsedTime().asSeconds();
        clock.restart();
        timer += time;

        Event e;
        while(window.pollEvent(e)) {
            if(e.type == Event::Closed) window.close();
        }

        if(Keyboard::isKeyPressed(Keyboard::Left)) dir = 1;
        if(Keyboard::isKeyPressed(Keyboard::Right)) dir = 2;
        if(Keyboard::isKeyPressed(Keyboard::Up)) dir = 3;
        if(Keyboard::isKeyPressed(Keyboard::Down)) dir = 0;
        if(Keyboard::isKeyPressed(Keyboard::W)) dir = 3;
        if(Keyboard::isKeyPressed(Keyboard::D)) dir = 2;
        if(Keyboard::isKeyPressed(Keyboard::A)) dir = 1;
        if(Keyboard::isKeyPressed(Keyboard::S)) dir = 0;

        if(timer > delay) {
            timer = 0;
            Tick();
        }

        ////// draw  ///////
        window.clear();

        for(int i = 0; i < N; i++)
            for(int j = 0; j < M; j++) {
                sprite1.setPosition(i * size, j * size);
                window.draw(sprite1);
            }

        for(int i = 0; i < num; i++) {
            sprite2.setPosition(s[i].x * size, s[i].y * size);
            window.draw(sprite2);
        }

        sprite3.setPosition(f.x * size, f.y * size);
        window.draw(sprite3);

        window.display();
    }

    return 0;
}

Answer 1

In your Tick() function you can check whether the head bumps into anything after everything has moved in the given direction. If it does, let main() know about it somehow: for example, return a bool which expresses if the game is over. Let's say this bool is called over .

So, add if (over) { window.close(); } if (over) { window.close(); } inside your while (window.isOpen()) loop (right after calling Tick() ) to let main() reach return 0; and finish the program.

EDIT: Think about using std::deque for moving your snake using less code and time: you'd be able to just pop_back() the snake tile farthest from the head and push_front() the new tile where the head currently is (after a tick), simulating crawling one step forwards.

Anyway, after having moved your snake you can check each of its body tiles whether it has the same coordinates as its head. If it does, it means your snake crashed into its tail so the game is over.

// in Tick():
// ...other logic...
tiles.pop_back();
tiles.push_front(new_head_position);
for (/* each tile of your snake except its head */) {
  if (tile.x == head.x && tile.y == head.y) {
    return false; // game over
  }
}
return true; // everything is fine