在画布中,有一个图像,它在箭头键的事件上移动。 但它在firefox中闪烁,并且在chrome和ie上工作正常。
我不想要只清除画布部分的解决方案,因为我在画布中也添加了其他东西。
以下是我的代码:
var
velY = 0,
velX = 0,
speed = 2,
friction = 0.90,
keys = [],
canvas = document.getElementById("canvas"),
ctx = canvas.getContext("2d"),
playerDirection="img/player/player_back.png";
function update() {
if (keys[38]) {
if (velY > -speed) {
velY--;
playerDirection="img/player/player_back.png";
}
}
if (keys[40]) {
if (velY < speed) {
velY++;
playerDirection="img/player/player_front.png";
}
}
if (keys[39]) {
if (velX < speed) {
velX++;
playerDirection="img/player/player_right.png";
}
}
if (keys[37]) {
if (velX > -speed) {
velX--;
playerDirection="img/player/player_left.png";
}
}
velY *= friction;
y += velY;
velX *= friction;
x += velX;
if (x >= canvas.width - player.width) {
x = canvas.width - player.width;
} else if (x <= 5) {
x = 5;
}
if (y > canvas.height - player.height) {
y = canvas.height - player.height;
} else if (y <= 5) {
y = 5;
}
ctx.clearRect(0, 0, canvas.width, canvas.height);
playerObj = new Image();
playerObj.onload = function()
{
ctx.drawImage(playerObj, x, y);
};
playerObj.src = playerDirection;
}
update();
function handlerKeyDown(e)
{
keys[e.keyCode] = true;
}
function handlerKeyUp(e) {
keys[e.keyCode] = false;
}
谢谢你。
答案 0 :(得分:1)
这就是我对“缓存图像”的意思:
var images = {}; // This will contain the Image objects
// Other definitions...
function update() {
if (keys[38]) {
if (!images.back) {
// The image object hasn't been defined yet.
images.back = new Image();
images.back.src = "img/player/player_back.png";
}
playerObj = images.back;
}
// Other checks on the pressed keys
// ...
// Computations on the position...
if (!playerObj.naturalWidth) {
// If naturalWidth/Height is 0, then the image hasn't been loaded yet.
// We update the onload listener to draw in the right position.
playerObj.onload = function() {
ctx.drawImage(playerObj, x, y);
};
// The image has already been loaded, so we just draw it
} else ctx.drawImage(playerObj, x, y);
}
(作为对你的代码的警告,似乎你想要处理多个按下的键,但序列中上下左右的最后一个总是“胜过”其他键。这真的是你想要的?)