[英]Make a canvas object stop inside the canvas area?
基本上我做了一個小游戲,但是我想知道如何使我創建的對象不超出畫布的界限。 當他到達邊界時,我要他停下來。 任何幫助表示贊賞
嗨,我自己做了一個小演示游戲 。 在那個游戲中,您正在尋找什么。 工作演示,您可以在這里找到
所以我要做的是
1)跟蹤用戶鍵盤的按下
document.onkeydown = function(e) {
e = e || window.event;
if(e.keyCode == "37") player.move("left");
else if(e.keyCode == "38") player.move("up");
else if(e.keyCode == "39") player.move("right");
else if(e.keyCode == "40") player.move("down");
};
2)獲取玩家位置的基本配置(在我的情況中為中間)
var player = {
x: Math.round((w/2)/objectSizes),
y: Math.round((h/2)/objectSizes)
}
3)然后在功能play.move上我跟蹤方向並進行所有限制
player.move = function(direction){
/**
* A temporary object to hold the current x, y so if there is a collision with the new coordinates to fallback here
*/
var hold_player = {
x: player.x,
y: player.y
};
/**
* Decide here the direction of the user and do the neccessary changes on the directions
*/
switch(direction) {
case "left":
player.x -= speed / modifier;
if(player.currentDirection == "stand") {
player.currentDirection = "left-1";
} else if(player.currentDirection == "left-1") {
player.currentDirection = "left-2";
} else if(player.currentDirection == "left-2") {
player.currentDirection = "left-1";
} else {
player.currentDirection = "left-1";
}
break;
case "right":
player.x += speed / modifier;
if(player.currentDirection == "stand") {
player.currentDirection = "right-1";
} else if(player.currentDirection == "right-1") {
player.currentDirection = "right-2";
} else if(player.currentDirection == "right-2") {
player.currentDirection = "right-1";
} else {
player.currentDirection = "right-1";
}
break;
case "up":
player.y -= speed / modifier;
if(player.currentDirection == "stand") {
player.currentDirection = "up-1";
} else if(player.currentDirection == "up-1") {
player.currentDirection = "up-2";
} else if(player.currentDirection == "up-2") {
player.currentDirection = "up-1";
} else {
player.currentDirection = "up-1";
}
break;
case "down":
player.y += speed / modifier;
if(player.currentDirection == "stand") {
player.currentDirection = "down-1";
} else if(player.currentDirection == "down-1") {
player.currentDirection = "down-2";
} else if(player.currentDirection == "down-2") {
player.currentDirection = "down-1";
} else {
player.currentDirection = "down-1";
}
break;
}
/**
* if there is a collision just fallback to the temp object i build before while not change back the direction so we can have a movement
*/
if(check_collision(player.x, player.y)) {
player.x = hold_player.x;
player.y = hold_player.y;
}
/**
* If player finds the coordinates of pokeball the generate new one, play the sound and update the score
*/
if(player.x == pokeball.x && player.y == pokeball.y) { // found a pokeball !! create a new one
console.log("found a pokeball of "+pokeball.spritePosition+"! Bravo! ");
pokePick.pause();
pokePick.currentTime = 0;
pokePick.play();
score += 1;
pokeball.generatePosition();
}
update();
};
然后最后我有這個功能來檢查任何碰撞
/**
* Our function that decides if there is a collision on the objects or not
* @function
* @name check_collision
* @param {Integer} x - The x axis
* @param {Integer} y - The y axis
*/
function check_collision(x, y) {
var foundCollision = false;
if(((x > 3 && x < 9) && y == 6) || ((x > 4 && x < 9) && (y == 5 || y == 4 || y == 3))) { //collision on house
console.log("on house");
foundCollision = true;
}
if((x<1 || x>20) ||
(y<2 || y>20) ||
((y > 0 && y < 4) && (x == 20 || x == 19)) || //right corner
((y > 0 && y < 4) && (x == 2 || x == 3)) || //left corner
((y > 18) && (x == 2 || x == 3)) || //left corner
((x > 17) && (y == 19 || y == 20)) || //left corner
((x > 19) && (y == 17 || y == 18)) //left corner 2
) {
console.log("lost on the woods");
foundCollision = true
}
return foundCollision;
}
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