我只想在按下鼠标按钮时获得鼠标位置。
现在，当我按下鼠标时它可以获取坐标，但是当我按下时它无法停止
<!DOCTYPE HTML>
<html>
<head>
<body style="background-color:3F6E6F;">
<style>
body {
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<canvas id="myCanvas" width="1200" height="1000" onmousedown="mouseDown()" onmouseup="mouseUp()"></canvas>
<script>
function writeMessage(canvas, message) {
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
context.font = '18pt Calibri';
context.fillStyle = 'black';
context.fillText(message, 10, 25);
}
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
function mouseUp() {
canvas.removeEventListener('mousemove', mouseDown)
// alert('44')
}
function mouseDown() {
canvas.addEventListener('mousemove', function(evt) {
var mousePos = getMousePos(canvas, evt);
var message = 'Mouse position: ' + mousePos.x + ',' + mousePos.y;
writeMessage(canvas, message);
}, false);
}
</script>
</body>
</html>
最佳答案
您必须在function和addEventListener中都传递相同的参数removeEventListener才能起作用。试试这个：
function writeMessage(canvas, message) {
var context = canvas.getContext('2d');
context.clearRect(0, 0, canvas.width, canvas.height);
context.font = '18pt Calibri';
context.fillStyle = 'black';
context.fillText(message, 10, 25);
}
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
};
}
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
//create function here
function move(evt) {
var mousePos = getMousePos(canvas, evt);
var message = 'Mouse position: ' + mousePos.x + ',' + mousePos.y;
writeMessage(canvas, message);
}
function mouseUp() {
//pass the same arguments
canvas.removeEventListener('mousemove', move, false)
// alert('44')
}
function mouseDown() {
//pass the same arguments
canvas.addEventListener('mousemove', move, false);
}body {
background-color: 3F6E6F;
margin: 0px;
padding: 0px;
}
canvas {
background-color: green;
}<canvas id="myCanvas" width="1200" height="1000" onmousedown="mouseDown(event)" onmouseup="mouseUp(event)"></canvas>