javascript游戏的重新启动按钮

时间：2020-06-14 10:35:22

标签： javascript html

我有一个JavaScript蛇游戏，它是按照一个教程制作的。我需要帮助来实现我自己创建的重启按钮

var canvas = document.getElementById('game');
var context = canvas.getContext('2d');
// var startBtn = document.getElementById('startbutton')

var score = 0;

var grid = 16;
var count = 0;

var snake = {
  x: 160,
  y: 160,

  // snake velocity. moves one grid length every frame in either the x or y direction
  dx: grid,
  dy: 0,

  // keep track of all grids the snake body occupies
  cells: [],

  // length of the snake. grows when eating an apple
  maxCells: 4
};
var apple = {
  x: 320,
  y: 320
};

function update(score) {
  document.getElementById("scores").innerHTML = "Score: " + score;

}

// get random whole numbers in a specific range
// @see https://stackoverflow.com/a/1527820/2124254
function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
}


// game loop
function loop() {
  update(score)
  requestAnimationFrame(loop);

  // slow game loop to 15 fps instead of 60 (60/15 = 4)
  if (++count < 5) {
    return;

  }


  count = 0;
  context.clearRect(0, 0, canvas.width, canvas.height);

  // move snake by it's velocity
  snake.x += snake.dx;
  snake.y += snake.dy;

  // wrap snake position horizontally on edge of screen
  if (snake.x < 0) {
    snake.x = canvas.width - grid;
  } else if (snake.x >= canvas.width) {
    snake.x = 0;
  }

  // wrap snake position vertically on edge of screen
  if (snake.y < 0) {
    snake.y = canvas.height - grid;
  } else if (snake.y >= canvas.height) {
    snake.y = 0;
  }

  // keep track of where snake has been. front of the array is always the head
  snake.cells.unshift({
    x: snake.x,
    y: snake.y
  });

  // remove cells as we move away from them
  if (snake.cells.length > snake.maxCells) {
    snake.cells.pop();
  }

  // draw apple
  context.fillStyle = 'red';
  context.fillRect(apple.x, apple.y, grid - 1, grid - 1);

  // draw snake one cell at a time
  context.fillStyle = 'green';
  snake.cells.forEach(function(cell, index) {

    // drawing 1 px smaller than the grid creates a grid effect in the snake body so you can see how long it is
    context.fillRect(cell.x, cell.y, grid - 1, grid - 1);

    // snake ate apple
    if (cell.x === apple.x && cell.y === apple.y) {
      snake.maxCells++;
      score++;

      // canvas is 400x400 which is 25x25 grids 
      apple.x = getRandomInt(0, 25) * grid;
      apple.y = getRandomInt(0, 25) * grid;
    }

    // check collision with all cells after this one (modified bubble sort)
    for (var i = index + 1; i < snake.cells.length; i++) {

      // snake occupies same space as a body part. reset game
      if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
        again()
        snake.x = 160;
        snake.y = 160;
        snake.cells = [];
        snake.maxCells = 4;
        snake.dx = grid;
        snake.dy = 0;

        apple.x = getRandomInt(0, 25) * grid;
        apple.y = getRandomInt(0, 25) * grid;
        score = 0
        // startBtn.style.display: 'none';
        // document.getElementById('start')

      }
    }
  });
}

// listen to keyboard events to move the snake
document.addEventListener('keydown', function(e) {
  // prevent snake from backtracking on itself by checking that it's 
  // not already moving on the same axis (pressing left while moving
  // left won't do anything, and pressing right while moving left
  // shouldn't let you collide with your own body)

  // left arrow key
  if (e.which === 37 && snake.dx === 0) {
    snake.dx = -grid;
    snake.dy = 0;
  }
  // up arrow key
  else if (e.which === 38 && snake.dy === 0) {
    snake.dy = -grid;
    snake.dx = 0;
  }
  // right arrow key
  else if (e.which === 39 && snake.dx === 0) {
    snake.dx = grid;
    snake.dy = 0;
  }
  // down arrow key
  else if (e.which === 40 && snake.dy === 0) {
    snake.dy = grid;
    snake.dx = 0;
  }
});

// start the game
// document.getElementById("scores").innerHTML = score;
function again() {
  document.getElementById("start").addEventListener("click", function restart() {
    requestAnimationFrame(loop);

  })
}
again()
html,
body {
  height: 100%;
  margin: 0;
}

body {
  background: black !important;
  display: flex;
  align-items: center;
  justify-content: center;
}

canvas {
  border: 1px solid white;
}

a {
  align-items: left;
}

#cent {
  position: absolute;
  margin-left: 20px;
  margin-right: 20px;
  margin-bottom: 50px;
  bottom: 0;
}

#startbutton {
  border: none;
  background: none;
  position: absolute;
  top: 50%;
  left: 50%;
  z-index: 1;
  transform: translate(-50%, -50%);
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
}

#start {
  border: none;
  background: none;
  position: absolute;
  top: 50%;
  left: 50%;
}
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
<title>RBGamez</title>
<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>

<div id="cent">
  <a href="{{url_for('home')}}"><button type="button" class="btn btn-primary">Return home</button></a>
</div>
<div style="position: absolute; left: 45%; top: 50px; width:200px; height:100px;">
  <h3>
    <p id="scores" style="color: white;"></p>
  </h3>
</div>

<button type="button" class="btn btn-primary" id="start" onclick="requestAnimationFrame(loop)">Restart</button>
<canvas width="400" height="400" id="game"></canvas>

1 个答案:

答案 0 :(得分：0)

检查。通过实施以下方法解决了速度增加的问题：https://stackoverflow.com/a/10748750/9487478

在“打开”按钮上按下again方法将立即触发。此外，我为apple和snake添加了用于重置对象的初始值。

var canvas = document.getElementById('game');
var context = canvas.getContext('2d');
// var startBtn = document.getElementById('startbutton')

var requestId;

var score = 0;

var grid = 16;
var count = 0;

var snake;
var snake_init = {
  x: 160,
  y: 160,

  // snake velocity. moves one grid length every frame in either the x or y direction
  dx: grid,
  dy: 0,

  // keep track of all grids the snake body occupies
  cells: [],

  // length of the snake. grows when eating an apple
  maxCells: 4
};

var apple;
var apple_init = {
  x: 320,
  y: 320
};

function update(score) {
  document.getElementById("scores").innerHTML = "Score: " + score;

}

// get random whole numbers in a specific range
// @see https://stackoverflow.com/a/1527820/2124254
function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
}

// game loop
function loop() {
  requestId = undefined;
  start();
  update(score)

  // slow game loop to 15 fps instead of 60 (60/15 = 4)
  if (++count < 5) {
    return;

  }


  count = 0;
  context.clearRect(0, 0, canvas.width, canvas.height);

  // move snake by it's velocity
  snake.x += snake.dx;
  snake.y += snake.dy;

  // wrap snake position horizontally on edge of screen
  if (snake.x < 0) {
    snake.x = canvas.width - grid;
  } else if (snake.x >= canvas.width) {
    snake.x = 0;
  }

  // wrap snake position vertically on edge of screen
  if (snake.y < 0) {
    snake.y = canvas.height - grid;
  } else if (snake.y >= canvas.height) {
    snake.y = 0;
  }

  // keep track of where snake has been. front of the array is always the head
  snake.cells.unshift({
    x: snake.x,
    y: snake.y
  });

  // remove cells as we move away from them
  if (snake.cells.length > snake.maxCells) {
    snake.cells.pop();
  }

  // draw apple
  context.fillStyle = 'red';
  context.fillRect(apple.x, apple.y, grid - 1, grid - 1);

  // draw snake one cell at a time
  context.fillStyle = 'green';
  snake.cells.forEach(function(cell, index) {

    // drawing 1 px smaller than the grid creates a grid effect in the snake body so you can see how long it is
    context.fillRect(cell.x, cell.y, grid - 1, grid - 1);

    // snake ate apple
    if (cell.x === apple.x && cell.y === apple.y) {
      snake.maxCells++;
      score++;

      // canvas is 400x400 which is 25x25 grids 
      apple.x = getRandomInt(0, 25) * grid;
      apple.y = getRandomInt(0, 25) * grid;
    }

    // check collision with all cells after this one (modified bubble sort)
    for (var i = index + 1; i < snake.cells.length; i++) {

      // snake occupies same space as a body part. reset game
      if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
        again()
        snake.x = 160;
        snake.y = 160;
        snake.cells = [];
        snake.maxCells = 4;
        snake.dx = grid;
        snake.dy = 0;

        apple.x = getRandomInt(0, 25) * grid;
        apple.y = getRandomInt(0, 25) * grid;
        score = 0
        // startBtn.style.display: 'none';
        // document.getElementById('start')

      }
    }
  });
}

// listen to keyboard events to move the snake
document.addEventListener('keydown', function(e) {
  // prevent snake from backtracking on itself by checking that it's 
  // not already moving on the same axis (pressing left while moving
  // left won't do anything, and pressing right while moving left
  // shouldn't let you collide with your own body)

  // left arrow key
  if (e.which === 37 && snake.dx === 0) {
    snake.dx = -grid;
    snake.dy = 0;
  }
  // up arrow key
  else if (e.which === 38 && snake.dy === 0) {
    snake.dy = -grid;
    snake.dx = 0;
  }
  // right arrow key
  else if (e.which === 39 && snake.dx === 0) {
    snake.dx = grid;
    snake.dy = 0;
  }
  // down arrow key
  else if (e.which === 40 && snake.dy === 0) {
    snake.dy = grid;
    snake.dx = 0;
  }
});

function start() {
  if (!requestId) {
    requestId = window.requestAnimationFrame(loop);
  }
}

function stop() {
  if (requestId) {
    window.cancelAnimationFrame(requestId);
    requestId = undefined;
  }
}

// start the game
function again() {
  document.getElementById("start").addEventListener("click", function restart() {
    // -----------------
    // Reset all values.
    // -----------------

    // Let's make a deep copy of snake_init for resetting.
    snake = JSON.parse(JSON.stringify(snake_init));
    apple = { ...apple_init };
    score = 0;
    count = 0;
    stop();
    start();
  })
}
again()
<title></title><style>html,
body {
  height: 100%;
  margin: 0;
}

body {
  background: black !important;
  display: flex;
  align-items: center;
  justify-content: center;
}

canvas {
  border: 1px solid white;
}

a {
  align-items: left;
}

#cent {
  position: absolute;
  margin-left: 20px;
  margin-right: 20px;
  margin-bottom: 50px;
  bottom: 0;
}

#startbutton {
  border: none;
  background: none;
  position: absolute;
  top: 50%;
  left: 50%;
  z-index: 1;
  transform: translate(-50%, -50%);
  -webkit-transform: translate(-50%, -50%);
  -moz-transform: translate(-50%, -50%);
  -ms-transform: translate(-50%, -50%);
}

#start {
  border: none;
  background: none;
  position: absolute;
  top: 50%;
  left: 50%;
}
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
<title>RBGamez</title>
<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>

<div id="cent">
  <a href="{{url_for('home')}}"><button type="button" class="btn btn-primary">Return home</button></a>
</div>
<div style="position: absolute; left: 45%; top: 50px; width:200px; height:100px;">
  <h3>
    <p id="scores" style="color: white;"></p>
  </h3>
</div>

<button type="button" class="btn btn-primary" id="start" onclick="again">Restart</button>
<canvas width="400" height="400" id="game"></canvas>

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