它似乎是一个直截了当的想法，如果我想停止执行一个函数，我应该return false或只是return或调用函数undefined等...但不是在这种情况下
所以我有一个网站项目，我有一个蛇游戏，用户可以通过向上，向下，向左，按键进行交互。我的主要问题是游戏处于循环中，每当蛇撞到墙壁或自己吃掉时它就会重新启动。
所以这里是HTML代码
<canvas id="canvas" width="200" height="200"></canvas>
Javascript
$(document).ready(function(){
jQuery("#snake-game").on('click',function(e){
jQuery("div.over-over").removeClass('not-shown');
playGame();
});
function playGame(e) {
var canvas = jQuery("#canvas")[0];
var ctx = canvas.getContext("2d");
var w = jQuery("#canvas").width();
var h = jQuery("#canvas").height();
var halt = e;
//Lets save the cell width in a variable for easy control
var cw = 10;
var d;
var food;
//Lets create the snake now
var snake_array; //an array of cells to make up the snake
function init()
{
d = "right"; //default direction
create_snake();
create_food(); //Now we can see the food particle
//Lets move the snake now using a timer which will trigger the paint function
//every 60ms
if(typeof game_loop != "undefined") clearInterval(game_loop);
game_loop = setInterval(paint, 60);
}
function create_snake()
{
var length = 5; //Length of the snake
snake_array = []; //Empty array to start with
for(var i = length-1; i>=0; i--)
{
//This will create a horizontal snake starting from the top left
snake_array.push({x: i, y:0});
}
}
//Lets create the food now
function create_food()
{
food = {
x: Math.round(Math.random()*(w-cw)/cw),
y: Math.round(Math.random()*(h-cw)/cw),
};
//This will create a cell with x/y between 0-44
//Because there are 45(450/10) positions accross the rows and columns
}
//Lets paint the snake now
function paint()
{
//To avoid the snake trail we need to paint the BG on every frame
//Lets paint the canvas now
ctx.fillStyle = "white";
ctx.fillRect(0, 0, w, h);
ctx.strokeStyle = "black";
ctx.strokeRect(0, 0, w, h);
//The movement code for the snake to come here.
//The logic is simple
//Pop out the tail cell and place it infront of the head cell
var nx = snake_array[0].x;
var ny = snake_array[0].y;
//These were the position of the head cell.
//We will increment it to get the new head position
//Lets add proper direction based movement now
if(d == "right") nx++;
else if(d == "left") nx--;
else if(d == "up") ny--;
else if(d == "down") ny++;
//Lets add the game over clauses now
//This will restart the game if the snake hits the wall
//Lets add the code for body collision
//Now if the head of the snake bumps into its body, the game will restart
if(nx == -1 || nx == w/cw || ny == -1 || ny == h/cw || check_collision(nx, ny, snake_array))
{
//restart game
init();
//Lets organize the code a bit now.
return;
}
//Lets write the code to make the snake eat the food
//The logic is simple
//If the new head position matches with that of the food,
//Create a new head instead of moving the tail
if(nx == food.x && ny == food.y)
{
var tail = {x: nx, y: ny};
//Create new food
create_food();
}
else
{
var tail = snake_array.pop(); //pops out the last cell
tail.x = nx; tail.y = ny;
}
//The snake can now eat the food.
snake_array.unshift(tail); //puts back the tail as the first cell
for(var i = 0; i < snake_array.length; i++)
{
var c = snake_array[i];
//Lets paint 10px wide cells
paint_cell(c.x, c.y);
}
//Lets paint the food
paint_cell(food.x, food.y);
}
//Lets first create a generic function to paint cells
function paint_cell(x, y)
{
ctx.fillStyle = "blue";
ctx.fillRect(x*cw, y*cw, cw, cw);
ctx.strokeStyle = "white";
ctx.strokeRect(x*cw, y*cw, cw, cw);
}
function check_collision(x, y, array)
{
//This function will check if the provided x/y coordinates exist
//in an array of cells or not
for(var i = 0; i < array.length; i++)
{
if(array[i].x == x && array[i].y == y)
return true;
}
return false;
}
//Lets add the keyboard controls now
jQuery(document).keydown(function(e){
var key = e.which;
//We will add another clause to prevent reverse gear
if(key == "37" && d != "right") d = "left";
else if(key == "38" && d != "down") d = "up";
else if(key == "39" && d != "left") d = "right";
else if(key == "40" && d != "up") d = "down";
//The snake is now keyboard controllable
});
}
});
我想要的是让用户点击画布外的任何地方，该功能将停止执行。有任何想法吗？
答案 0 :(得分：0)
当您在画布外单击时，可以尝试停止游戏循环：原始代码 - ＆gt; give credit where credit is due
$(document).ready(function() {
$(document).click(function(e) {
if ($(e.target).closest('#canvas').length === 0) {
alert('out of the canvas');
clearInterval(game_loop);
}
});
$("#canvas").click(function(e) {
alert('click in the canvas');
game_loop = setInterval(paint, 60);
});
//Canvas stuff
var canvas = $("#canvas")[0];
var ctx = canvas.getContext("2d");
var w = $("#canvas").width();
var h = $("#canvas").height();
//Lets save the cell width in a variable for easy control
var cw = 10;
var d;
var food;
var score;
//Lets create the snake now
var snake_array; //an array of cells to make up the snake
function init() {
d = "right"; //default direction
create_snake();
create_food(); //Now we can see the food particle
//finally lets display the score
score = 0;
//Lets move the snake now using a timer which will trigger the paint function
//every 60ms
if (typeof game_loop != "undefined") clearInterval(game_loop);
game_loop = setInterval(paint, 60);
}
init();
function create_snake() {
var length = 5; //Length of the snake
snake_array = []; //Empty array to start with
for (var i = length - 1; i >= 0; i--) {
//This will create a horizontal snake starting from the top left
snake_array.push({
x: i,
y: 0
});
}
}
//Lets create the food now
function create_food() {
food = {
x: Math.round(Math.random() * (w - cw) / cw),
y: Math.round(Math.random() * (h - cw) / cw),
};
//This will create a cell with x/y between 0-44
//Because there are 45(450/10) positions accross the rows and columns
}
//Lets paint the snake now
function paint() {
//To avoid the snake trail we need to paint the BG on every frame
//Lets paint the canvas now
ctx.fillStyle = "white";
ctx.fillRect(0, 0, w, h);
ctx.strokeStyle = "black";
ctx.strokeRect(0, 0, w, h);
//The movement code for the snake to come here.
//The logic is simple
//Pop out the tail cell and place it infront of the head cell
var nx = snake_array[0].x;
var ny = snake_array[0].y;
//These were the position of the head cell.
//We will increment it to get the new head position
//Lets add proper direction based movement now
if (d == "right") nx++;
else if (d == "left") nx--;
else if (d == "up") ny--;
else if (d == "down") ny++;
//Lets add the game over clauses now
//This will restart the game if the snake hits the wall
//Lets add the code for body collision
//Now if the head of the snake bumps into its body, the game will restart
if (nx == -1 || nx == w / cw || ny == -1 || ny == h / cw || check_collision(nx, ny, snake_array)) {
//restart game
init();
//Lets organize the code a bit now.
return;
}
//Lets write the code to make the snake eat the food
//The logic is simple
//If the new head position matches with that of the food,
//Create a new head instead of moving the tail
if (nx == food.x && ny == food.y) {
var tail = {
x: nx,
y: ny
};
score++;
//Create new food
create_food();
} else {
var tail = snake_array.pop(); //pops out the last cell
tail.x = nx;
tail.y = ny;
}
//The snake can now eat the food.
snake_array.unshift(tail); //puts back the tail as the first cell
for (var i = 0; i < snake_array.length; i++) {
var c = snake_array[i];
//Lets paint 10px wide cells
paint_cell(c.x, c.y);
}
//Lets paint the food
paint_cell(food.x, food.y);
//Lets paint the score
var score_text = "Score: " + score;
ctx.fillText(score_text, 5, h - 5);
}
//Lets first create a generic function to paint cells
function paint_cell(x, y) {
ctx.fillStyle = "blue";
ctx.fillRect(x * cw, y * cw, cw, cw);
ctx.strokeStyle = "white";
ctx.strokeRect(x * cw, y * cw, cw, cw);
}
function check_collision(x, y, array) {
//This function will check if the provided x/y coordinates exist
//in an array of cells or not
for (var i = 0; i < array.length; i++) {
if (array[i].x == x && array[i].y == y)
return true;
}
return false;
}
//Lets add the keyboard controls now
$(document).keydown(function(e) {
var key = e.which;
//We will add another clause to prevent reverse gear
if (key == "37" && d != "right") d = "left";
else if (key == "38" && d != "down") d = "up";
else if (key == "39" && d != "left") d = "right";
else if (key == "40" && d != "up") d = "down";
//The snake is now keyboard controllable
})
})<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="canvas" width="200" height="200">
</canvas>