【发布时间】：2021-10-18 11:35:30
【问题描述】：
作为一个学校项目，我使用 SDL2 和 C++ 制作了经典的贪吃蛇游戏。 我已经为 Snake 实现了不断增长、移动的功能，但是需要基于网格进行移动，但是当我实现网格功能时，每当增长一个部分时，总是会触发自碰撞，所以每次我开始游戏，吃掉第一个水果，蛇就死了。
我已经尝试了一段时间，从放置延迟到添加尾部和延迟碰撞检查，但无济于事，它总是与自己碰撞，即使它不是。
我看不出自碰撞有什么问题，如果有人能指出问题所在，我将不胜感激。
Snake.h
#include "GameObject.h"
#include "common.h"
#include "draw.h"
#include "Food.h"
#include "util.h"
#include <vector>
struct Segment {
int x;
int y;
Segment(int posx, int posy) {
x = posx;
y = posy;
}
};
class Snake :
public GameObject
{
public:
~Snake();
void start();
void update();
void draw();
void outOfBoundsCheck();
void move();
void addSegment(int x, int y);
void selfCollisionCheck(bool hasEaten);
void setHasMoved(bool a);
void setIsAlive(bool a);
int getX();
int getY();
int getWidth();
int getHeight();
bool getIsAlive();
bool getHasMoved();
std::vector<Segment*> const& getV() const;
private:
std::vector<Segment*> body;
SDL_Texture* headTexture;
SDL_Texture* bodyTexture;
int x;
int y;
int width;
int height;
int dx;
int dy;
int tempX;
int tempY;
bool isAlive;
bool hasMoved;
};
Snake.cpp
Snake::~Snake()
{
}
void Snake::start()
{
// Load Texture
headTexture = loadTexture("gfx/player.png");
bodyTexture = loadTexture("gfx/body.png");
tempX = 0;
tempY = 0;
x = 0;
y = 0;
dx = 0;
dy = 0;
isAlive = true;
hasMoved = false;
width = 0;
height = 0;
SDL_QueryTexture(headTexture, NULL, NULL, &width, &height);
addSegment(x, y);
}
void Snake::update()
{
std::cout << "Head" << body[0]->x << std::endl;
if (body.size() > 1) {
std::cout << "2nd Segment" << body[1]->x << std::endl;
if (body.size() > 2) {
std::cout << "3nd Segment" << body[2]->x << std::endl;
}
}
move();
outOfBoundsCheck();
}
void Snake::draw()
{
if (!isAlive) return; // Cancel the render if player dies
for (int i = 0; i < body.size(); i++) {
blit(headTexture, body[i]->x, body[i]->y);
}
}
void Snake::outOfBoundsCheck()
{
for (int i = 0; i < body.size(); i++) {
if (body[i]->x > SCREEN_WIDTH) {
body[i]->x = 0;
}
if (body[i]->x < 0) {
body[i]->x = SCREEN_WIDTH;
}
if (body[i]->y > SCREEN_HEIGHT) {
body[i]->y = 0;
}
if (body[i]->y < 0) {
body[i]->y = SCREEN_HEIGHT;
}
}
}
void Snake::move()
{
if (app.keyboard[SDL_SCANCODE_W] && dy != 5) {
dx = 0;
dy = -5;
}
if (app.keyboard[SDL_SCANCODE_A] && dx != 5) {
dx = -5;
dy = 0;
}
if (app.keyboard[SDL_SCANCODE_S] && dy != -5) {
dx = 0;
dy = 5;
}
if (app.keyboard[SDL_SCANCODE_D] && dx != -5) {
dx = 5;
dy = 0;
}
Segment* snakeHead = *(body.begin()); //Grid
tempX += dx;
tempY += dy;
if (tempX % 25 == 0) {
snakeHead->x += tempX;
tempX = 0;
}
if (tempY % 25 == 0) {
snakeHead->y += tempY;
tempY = 0;
}
for (int i = body.size() - 1; i > 0; i--) { //For the other parts to follow
body[i]->x = body[i - 1]->x;
body[i]->y = body[i - 1]->y;
}
}
void Snake::addSegment(int x, int y)
{
Segment* seg = new Segment(x, y );
body.push_back(seg);
}
void Snake::selfCollisionCheck(bool hasEaten) // Fail
{
Segment* head = body[0];
if (hasEaten == false) {
for (int i = 1; i < body.size(); i++) {
if (head->x == body[i]->x && head->y == body[i]->y) {
isAlive = false;
break;
}
}
}
else {
return;
}
}
void Snake::setHasMoved(bool a)
{
hasMoved = a;
}
void Snake::setIsAlive(bool a)
{
isAlive = a;
}
int Snake::getX()
{
return x;
}
int Snake::getY()
{
return y;
}
int Snake::getWidth()
{
return width;
}
int Snake::getHeight()
{
return height;
}
bool Snake::getIsAlive()
{
return isAlive;
}
bool Snake::getHasMoved()
{
return hasMoved;
}
std::vector<Segment*> const& Snake::getV() const
{
// TODO: insert return statement here
return body;
}
GameScene.h
#include "Scene.h"
#include "GameObject.h"
#include "Snake.h"
#include "Food.h"
#include "util.h"
#include "text.h"
#include "SoundManager.h"
class GameScene : public Scene
{
public:
GameScene();
~GameScene();
void start();
void draw();
void update();
void spawnFood();
void collisionLogic();
void selfCollision();
void despawnFood(Food* food);
private:
Snake* snake;
Food* food;
int points;
std::vector<Food*> spawnedFood;
};
GameScene.cpp
#include "GameScene.h"
GameScene::GameScene()
{
// Register and add game objects on constructor
snake = new Snake();
this->addGameObject(snake);
points = 0;
}
GameScene::~GameScene()
{
delete snake;
delete food;
}
void GameScene::start()
{
Scene::start();
// Initialize any scene logic here
initFonts();
spawnFood();
}
void GameScene::draw()
{
Scene::draw();
drawText(110, 20, 255, 255, 255, TEXT_CENTER, "POINTS: %03d", points);
if (snake->getIsAlive() == false) {
drawText(SCREEN_WIDTH / 2, SCREEN_HEIGHT / 2, 255, 255, 255, TEXT_CENTER, "GAME OVER!");
}
}
void GameScene::update()
{
Scene::update();
if (spawnedFood.size() == 0 && spawnedFood.size() != 1) {
spawnFood();
}
collisionLogic();
selfCollision();
}
void GameScene::spawnFood()
{
int random = rand() % 720;
if (random % 25 != 0) {
random = rand() % 720;
}
else {
Food* food = new Food();
this->addGameObject(food);
food->setPosition(rand() % SCREEN_WIDTH, rand() % SCREEN_HEIGHT);
spawnedFood.push_back(food);
}
}
void GameScene::collisionLogic()
{
Segment* head = snake->getV()[0];
std::vector<Segment*> snakeBody = snake->getV();
for (int i = 0; i < objects.size(); i++) {
Food* food = dynamic_cast<Food*>(objects[i]);
if (food != NULL) {
int collision = checkCollision(
head->x, head->y, snake->getWidth(), snake->getHeight(),
food->getX(), food->getY(), food->getWidth(), food->getHeight()
);
if (collision == 1) {
despawnFood(food);
snake->addSegment(snakeBody[snakeBody.size() - 1]->x, snakeBody[snakeBody.size() - 1]->y); //Adds a part to the snake
points++;
break;
}
}
}
}
void GameScene::selfCollision()
{
std::vector<Segment*> body = snake->getV();
Segment* head = snake->getV()[0];
for (int i = 1; i < snake->getV().size(); i++) {
if (head->x == body[i]->x && head->y == body[i]->y) {
snake->setIsAlive(false);
break;
}
}
}
void GameScene::despawnFood(Food* food)
{
int index = -1;
for (int i = 0; i < spawnedFood.size(); i++) {
if (food == spawnedFood[i]) {
index = i;
break;
}
}
if (index != -1) {
spawnedFood.erase(spawnedFood.begin() + index);
delete food;
}
}
【问题讨论】：
-
[OT]：避免原始的拥有指针，更喜欢
std::unique_ptr或直接取值：std::vector<Segment*>可以是std::vector<Segment>，Snake* snake可能是Snake snake，std::vector<Food*> spawnedFood;可能是@ 987654331@（这里不是按值，因为您也将指针存储在游戏对象中，并且调整向量的大小会使指针无效）。 -
void Snake::selfCollisionCheck(bool hasEaten)在您发布的代码中未调用。而void GameScene::selfCollision()似乎重新实现了相同的逻辑 -
您可能需要添加更多
couts 来检查状态。一个注释，不确定它是否与您报告的问题有关：outOfBoundsCheck()，if (body[i]->x < 0) { body[i]->x = SCREEN_WIDTH; }不应该是SCREEN_WIDTH - 1吗？和高度一样。 -
对于那些重复的功能我感到非常抱歉，那些是我尝试修复碰撞错误的失败尝试，但感谢您指出它们！我现在将它们删除。另外，感谢您检查我的 outOfBoundsCheck()，我想知道为什么蛇会越界，检查它！
-
基于我的断点。当我与水果相撞的那一刻，bodySize 增加到两个，因此这留下了 [0] 的头部和新添加的段 [1]，问题是 [0] 的 x 和 y 坐标是相同的作为 [1] 并且当我禁用碰撞检查时，它还显示 [0] [1] [2] 的 sx 和 y 坐标相同，并且这种情况一直持续下去。它们仅在涉及方向变化时有所不同，并且它们在一些帧后再次均衡。