javascript setTimeout()不工作，图像不移动

rvpgvaaj 于 2023-03-28 发布在 Java

关注(0)|答案(1)|浏览(95)

我的密码是

<script>
  var theCanvas = document.getElementById("theCanvas");
  var theContext = theCanvas.getContext("2d");
  var theImage = document.getElementById("frog");
  var x = 300;
  var y = 50;
  moveProjectile();

  function drawProjectile() {
    theContext.drawImage(theImage,6,450,100,100);
  }
  function moveProjectile() {
    x += 1;
    drawProjectile();
    window.setTimeout(moveProjectile, 1000/30);
  }
</script>

我已经尝试了几种方法，包括重新定位setTimeout（）并将其替换为setInterval（），但都不起作用，MDM也没有帮助。

JavaScript

来源：https://stackoverflow.com/questions/75845409/settimeout-not-working-and-image-not-moving

1条答案

按热度按时间

nle07wnf1#

您需要将更新后的x坐标传递给drawImage。此外，每次在下一个位置绘制图像之前，请清除画布。
(You也应该考虑使用requestAnimationFrame而不是setTimeout或setInterval。）

const theCanvas = document.getElementById("theCanvas");
const theContext = theCanvas.getContext("2d");
const theImage = document.getElementById("frog");
let x = 0;
let y = 50;
moveProjectile();

function drawProjectile() {
  theContext.clearRect(0, 0, theCanvas.width, theCanvas.height);
  theContext.drawImage(theImage, x, y, 100, 100);
}

function moveProjectile() {
  x++;
  drawProjectile();
  window.setTimeout(moveProjectile, 1000 / 30);
}

<canvas id="theCanvas"></canvas>
<img id="frog" src="https://static.scientificamerican.com/sciam/cache/file/41DF7DA0-EE58-4259-AA815A390FB37C55_source.jpg" style="display: none;">

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javascript setTimeout()不工作，图像不移动

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