【发布时间】：2019-04-07 17:58:45
【问题描述】：
我正在尝试制作一些按钮来控制画布中的某些内容。我希望它们出现在画布的右侧，所以我使用 css 来设置和移动它们。我还制作了一个计时器，它在按下绿色按钮 START 时启动，在按下 FINISH 时停止。我的问题是当我移动到正确的位置时，第一个按钮不起作用或按下。你知道为什么会这样吗？这是我所说的代码的一部分。提前谢谢！！！
document.body.style.backgroundColor = "#FAFAD2";
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
window.requestAnimFrame = (function(callback) {
return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
var startTime = Date.now();
var t;
var timer_is_on = 0;
function timedCount() {
var elapsedTime = Date.now() - startTime;
document.getElementById("timer").innerHTML = (elapsedTime / 1000).toFixed(3);
t = setTimeout("timedCount()", 100);
}
function doTimer() {
if (!timer_is_on) {
timer_is_on = 1;
timedCount();
}
}
function stopCount() {
clearTimeout(t);
timer_is_on = 0;
}
$('#start').on('click', function() {
doTimer();
});
$('#finish').on('click', function() {
stopCount();
});.timer {
position: absolute;
bottom: 55px;
left: 600px;
}
.both,
.one,
.two,
.timer {
display: block;
padding: 30px;
position: absolute;
left: 600px;
}
.both button {
background-color: #4CAF50;
border: 1px solid black;
margin-left: 50px;
color: white;
padding: 15px 10px;
text-align: center;
font-size: 16px;
font-weight: bold;
cursor: pointer;
width: 100px;
display: block;
position: relative;
bottom: 20px;
}
.one button {
border: 1px solid black;
color: white;
padding: 15px 5px;
text-align: center;
font-size: 16px;
font-weight: bold;
cursor: pointer;
width: 200px;
display: block;
position: relative;
top: 100px;
}
.two button {
border: 1px solid black;
color: white;
padding: 15px 5px;
text-align: center;
font-size: 16px;
font-weight: bold;
cursor: pointer;
width: 200px;
display: block;
position: relative;
top: 300px;
}
.timer button {
background-color: #696969;
border: 1px solid black;
color: white;
padding: 12px 8px;
text-align: center;
font-size: 15px;
font-weight: bold;
cursor: pointer;
width: 80px;
}<!DOCTYPE html>
<html>
<head>
<title> Simulation </title>
</head>
<body>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<div class='both'>
<button type='button' id='start'>START</button>
<button type='button' id='stop'>STOP</button>
</div>
<div class='one'>
<button type='button' id='start1' style='background-color:#B22222;'>START 1</button>
<button type='button' id='stop1' style='background-color:#B22222;'>STOP 1</button>
<button type='button' id='position1' style='background-color:#B22222;'>POSITION 1</button>
</div>
<div class='two'>
<button type='button' id='start2' style='background-color:#FFD700;'>START 2</button>
<button type='button' id='stop2' style='background-color:#FFD700;'>STOP 2</button>
<button type='button' id='position2' style='background-color:#FFD700;'>POSITION 2</button>
</div>
<div class='timer'>
<span id="timer"></span> sec
<button type='button' id='finish'>FINISH</button>
</div>
<br>
<canvas id="myCanvas" width="455" height="650" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
</body>
</html>【问题讨论】：
-
timer_is_on不是boolen值。 -
@SalomonZhang 但是
0是falsy 而1是truthy。 sitepoint.com/javascript-truthy-falsy
标签： javascript jquery css html html5-canvas