0 
<html>
<header>
<link href='css.css' rel='stylesheet'>
<meta charset="UTF-8">
<title> moving box </title>

<script type= 'text/javascript'>


var rectangle = {
x: 100,
y: 100,
width: 100,
height: 100,
};

var mx = 4;
var my = 4;
var cheight = 700;
var cwidth = 700;
var e = event.keyCode;

function checkmx() {
if (rectangle.x + 100 > cwidth){
mx = -4;
}
if (rectangle.x < 0){
mx = 4;
}
}

function checkmy() {
if (rectangle.y + 100 > cheight){
my = -4;
}
if (rectangle.y < 0){
my = 4;
}
}
function keydowncontrol(){

if (e == 37){
mx = -1;
my = 0;
}
if (e == 38){
mx = 0;
my = -1;
}
if (e == 39){
mx = 1;
my = 0;
}
if (e == 40){
mx = 0;
my = 1;
}
//if (e == 35){
//mx = 0
//mx = 0
//}
}
function draw() {
checkmx();
checkmy();
keydowncontrol();

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var nextx = rectangle.x + mx;
var nexty = rectangle.y + my;

rectangle.x = nextx
rectangle.y = nexty
ctx.clearRect(0, 0, cwidth, cheight);

ctx.beginPath();
ctx.rect(rectangle.x, rectangle.y, rectangle.width, rectangle.height);
ctx.fillStyle = '#FF0000';
ctx.fill();
ctx.stroke();
}

function init() {

checkmx();
checkmy();
window.onkeydown = keydowncontrol();// how can does this notice the key pressed
draw();
}


</script>
</header>
<body onload='setInterval(init,10)'>
<canvas id="canvas" width="700" height="700"></canvas>
</body>
</html>

我正在尝试为一个盒子制作动画。我不确定window.onkeydownand是如何event.keycode工作的。我的目标是让mx和my变量根据按下的键而改变。应该keydowncontrol()在draw()函数还是init()函数中？

4

1 回答 1

0

Try this:

<html>
<head>
    <link href='css.css' rel='stylesheet' />
    <meta charset="UTF-8" />
    <title>Moving box</title>
    <script type='text/javascript'>
        var rectangle = {
            x: 100,
            y: 100,
            width: 100,
            height: 100
        };

        var mx = 4;
        var my = 4;
        var cheight = 700;
        var cwidth = 700;
        var e = event.keyCode;

        function checkmx() {
            if (rectangle.x + 100 > cwidth) {
                mx = -4;
            }
            if (rectangle.x < 0) {
                mx = 4;
            }
        }

        function checkmy() {
            if (rectangle.y + 100 > cheight) {
                my = -4;
            }
            if (rectangle.y < 0) {
                my = 4;
            }
        }

        function keydowncontrol(e) {
            //alert(e);
            if (e.keyCode == 37) {
                mx = -1;
                my = 0;
            }
            if (e.keyCode == 38) {
                mx = 0;
                my = -1;
            }
            if (e.keyCode == 39) {
                mx = 1;
                my = 0;
            }
            if (e.keyCode == 40) {
                mx = 0;
                my = 1;
            }
            //if (e == 35){
            //mx = 0
            //mx = 0
            //}
        }

        function draw() {
            checkmx();
            checkmy();
            //keydowncontrol();

            var canvas = document.getElementById("canvas");
            var ctx = canvas.getContext("2d");
            var nextx = rectangle.x + mx;
            var nexty = rectangle.y + my;

            rectangle.x = nextx
            rectangle.y = nexty
            ctx.clearRect(0, 0, cwidth, cheight);

            ctx.beginPath();
            ctx.rect(rectangle.x, rectangle.y, rectangle.width, rectangle.height);
            ctx.fillStyle = '#FF0000';
            ctx.fill();
            ctx.stroke();
        }

        //document.attachEvent("onkeypress", keydowncontrol);
    </script>
</head>
<body onload='setInterval(draw, 10)' onkeydown="keydowncontrol(event)">
    <canvas id="canvas" width="700" height="700"></canvas>
</body>
</html>
于 2013-10-29T02:32:27.307 回答