蛇游戏 - 无法让蛇身跟随蛇头

Question

I have been working on a snake game using sfml and c++ but I am having trouble getting the tail of my snake to follow the snake head which is defined as Snake[0] in my code below. I have implemented code that I think should work but doesn't which is the following

    for (int i = 1; i < snakeSize; i++)
    {
        snakePartX[i] = snakePartX[i-1];
        snakePartY[i] = snakePartY[i-1];
    }

The way I understand it (and I am probably incredibly wrong and would appreciate if anyone could point out what is actually happening here) is that, that piece of code should set the value of a snake body part to the position of where the previous body part WAS located so that when the program loops they are set to follow the snake as it travels.

What actually does happen though is that when the snake eats an apple the snake will gain 1 block to its tail, but will not grow any farther.

Answer 1

In the classic snake game, the snake is made up of segments. Each segment contains the coordinate of the segment (among other attributes).

Specifically, the snake is a container of segments. The container is your choice, but I recommend a queue.

With the queue, a new head segment is added into the queue and a tail segment removed.

Here's a code fragment to help:

class Snake_Segment
{
  public:
    int column;
    int row;
};

typedef std::deque<Snake_Segment> Segment_Container;

int main(void)
{
  Segment_Container snake_body;
  Snake_Segment head;
  head.row(25);
  head.column(30);
  snake_body.push_back(head);
  Snake_Segment tail = head;
  ++tail.column;
  snake_body.push_back(tail);
  return EXIT_SUCCESS;
}

Answer 2

Why do index zero here? Doesn't it get done as part of the for loop too?

        Snake[0].setPosition(snakePartX[0], snakePartY[0]);

        for(int i = 0; i < snakeSize; i++)
        {
            Snake[i].setPosition(snakePartX[i], snakePartY[i]);
        }

I'm concerned about this section :

        snakeSize += 1;
    }

    Apple.setPosition(applePos.x, applePos.y);
    window.draw(Apple);

    for(int i = 0; i < snakeSize; i++)
    {
        window.draw(Snake[i]);
    }

Make sure you don't exceed 20 as your parts are a simple array and you will run into problems once you get 20 parts. More importantly, you never set the value for Snake[i] for the new snakeSize. So when you get an apple, you'll use uninitialized memory to draw one snake part.

Another potential problem :

    //Clock to set snake speed
    ElapsedTime = clock.getElapsedTime();
    if(ElapsedTime.asSeconds() >= snakeSpeed)
    {

        for(int i = 1; i < snakeSize; i++)
        {
            snakePartX[i] = snakePartX[i - 1];
            snakePartY[i] = snakePartY[i - 1];
        }

You allow keyboard input to move the snake head along, but you only move the body when the timer expires. So you head can slide way away from the body and the body doesn't move unless the timer goes off.

Answer 3

I printed the field of snake game as a Field[x][y] . So by below code the body of snake following the head. Also, optionMoveNumber==0 in other function checked if Field[x][y]==food or not which means did the snake eat the food of not.

int m=1;
void Snake::Movement(int x, int y){
        movey[0]=firstTaily; //first place
        movex[0]=firstTailx; //first place
        movex[m]=x;
        movey[m]=y; 
        for(int n=m; n>=m-ntail; n--){
        Field[movey[n]][movex[n]]=Field[movey[n-1]][movex[n-1]];
    }
    if(optionMoveNumber==0){
        Field[movey[m-1]][movex[m-1]]=tail;
    }
    else{
        Field[movey[m-ntail-1]][movex[m-ntail-1]]=space;
    }
    m++;

}