Javascript 在 HTML5 画布中创建关键事件的最佳方法是什么？
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时间：2020-08-23 07:29:12 来源:igfitidea点击:
What's the best way to create key events in HTML5 canvas?
提问by user1441816
Please suggest the best way to create key events for HTML5 canvas. I don't prefer any library, but if you think that it's the best way then go answer it. Thanks in advance!
请建议为 HTML5 画布创建关键事件的最佳方法。我不喜欢任何图书馆，但如果你认为这是最好的方法，那就去回答吧。提前致谢！
回答by Rhyono
This will return the key code:
这将返回密钥代码：
<canvas id="myCanvas" width="200" height="100" style="background:green"></canvas>
<script type="text/javascript">
window.addEventListener('keydown',this.check,false);
function check(e) {
alert(e.keyCode);
}
</script>
If you would like a demonstration of different things being done based on key:
如果您想演示基于密钥所做的不同事情：
function check(e) {
var code = e.keyCode;
//Up arrow pressed
if (code == 38)
alert("You pressed the Up arrow key");
else
alert("You pressed some other key I don't really care about.");
}
Or if you have a long list of keys you'll be using, do it in a switch case:
或者，如果您要使用的键列表很长，请在开关盒中进行操作：
function check(e) {
var code = e.keyCode;
switch (code) {
case 37: alert("Left"); break; //Left key
case 38: alert("Up"); break; //Up key
case 39: alert("Right"); break; //Right key
case 40: alert("Down"); break; //Down key
default: alert(code); //Everything else
}
}
回答by Brian Duncan
If you want to set key event handling on the <canvas>itself (not the windowor document), set a tabindex on the <canvas>element. Note that the canvas will need to be in focus on to catch key events.
如果要在其<canvas>本身（而不是window或document）上设置键事件处理，请在<canvas>元素上设置 tabindex 。请注意，需要关注画布以捕捉关键事件。
<script>
document.getElementById('game').addEventListener('keypress', handleKeyPress);
function handleKeyPress(e) { ... }
</script>
<canvas id="game" tabindex="1" width="350" height="200">
</canvas>
This is how it is done on the Processing.jswebsite.
这是在Processing.js网站上完成的方式。
If you don't want a border to appear when you click on the canvas, set its style to outline: none.
如果您不想在单击画布时出现边框，请将其样式设置为outline: none。
回答by Polyov
I'm writing a Canvas game, and I use the default .addEventListenerand shift through the event.keyCodes that come with it. Further, I don't listen for key events on the Canvas element its self, rather just set the listener to the window.
我正在编写一个 Canvas 游戏，我使用默认值.addEventListener并切换event.keyCode它附带的s。此外，我不会自己监听 Canvas 元素上的关键事件，而只是将监听器设置为窗口。
window.addEventListener('keyup',keyUpListener,false);
window.addEventListener('keydown',keyDownListener,false);
回答by Nikola Lukic
Usage of class:
类的用法：
var CONTROL = MOBILE_CONTROL();
Look at this class:
看看这个类：
function MOBILE_CONTROL (){
this.X = null;
this.Y = null;
this.LAST_X_POSITION = null;
this.LAST_Y_POSITION = null;
this.MULTI_TOUCH = 'NO';
this.MULTI_TOUCH_X1 = null;
this.MULTI_TOUCH_X2 = null;
this.MULTI_TOUCH_X3 = null;
this.MULTI_TOUCH_X4 = null;
this.MULTI_TOUCH_X5 = null;
this.MULTI_TOUCH_Y1 = null;
this.MULTI_TOUCH_Y2 = null;
this.MULTI_TOUCH_Y3 = null;
this.MULTI_TOUCH_Y4 = null;
this.MULTI_TOUCH_Y5 = null;
this.MULTI_TOUCH_X6 = null;
this.MULTI_TOUCH_X7 = null;
this.MULTI_TOUCH_X8 = null;
this.MULTI_TOUCH_X9 = null;
this.MULTI_TOUCH_X10 = null;
this.MULTI_TOUCH_Y6 = null;
this.MULTI_TOUCH_Y7 = null;
this.MULTI_TOUCH_Y8 = null;
this.MULTI_TOUCH_Y9 = null;
this.MULTI_TOUCH_Y10 = null;
this.MULTI_TOUCH_INDEX = 1;
this.SCREEN = [window.innerWidth , window.innerHeight];
this.SCREEN.W = this.SCREEN[0];
this.SCREEN.H = this.SCREEN[1];
//Application general
this.AUTOR = "Nikola Lukic";
this.APPLICATION_NAME = "mobile multi touch , system plugin for visual js .";
}
var CONTROL = new MOBILE_CONTROL();
document.addEventListener('touchstart', function(event)
{
if (CONTROL.MULTI_TOUCH == 'NO') {
var touch = event.touches[0];
CONTROL.X = touch.pageX;
CONTROL.Y = touch.pageY;
console.log('TOUCH START AT:(X' + CONTROL.X + '),(' + CONTROL.Y + ')' );
}
else if (CONTROL.MULTI_TOUCH == 'YES') {
var touches_changed = event.changedTouches;
for (var i=0; i<touches_changed.length;i++) {
//CONTROL.MULTI_TOUCH_X1
console.log("multi touch : x" + CONTROL.MULTI_TOUCH_INDEX + ":(" +touches_changed[i].pageX + ")");
switch(CONTROL.MULTI_TOUCH_INDEX)
{
case 1:
CONTROL.MULTI_TOUCH_X1=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y1=touches_changed[i].pageY;
break;
case 2:
CONTROL.MULTI_TOUCH_X2=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y2=touches_changed[i].pageY;
break;
case 3:
CONTROL.MULTI_TOUCH_X3=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y3=touches_changed[i].pageY;
break;
case 4:
CONTROL.MULTI_TOUCH_X4=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y4=touches_changed[i].pageY;
break;
case 5:
CONTROL.MULTI_TOUCH_X5=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y5=touches_changed[i].pageY;
break;
case 6:
CONTROL.MULTI_TOUCH_X6=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y6=touches_changed[i].pageY;
break;
case 7:
CONTROL.MULTI_TOUCH_X7=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y7=touches_changed[i].pageY;
break;
case 8:
CONTROL.MULTI_TOUCH_X8=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y8=touches_changed[i].pageY;
break;
case 9:
CONTROL.MULTI_TOUCH_X9=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y9=touches_changed[i].pageY;
break;
case 10:
CONTROL.MULTI_TOUCH_X10=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y10=touches_changed[i].pageY;
break;
default:
//code to be executed if n is different from case 1 and 2
}
CONTROL.MULTI_TOUCH_INDEX = CONTROL.MULTI_TOUCH_INDEX + 1;
}
}
CONTROL.MULTI_TOUCH = 'YES';
},false);
////////////////////////////////////////////////////////
document.addEventListener('touchmove', function(event)
{
var touch = event.touches[0];
CONTROL.X = touch.pageX;
CONTROL.Y = touch.pageY;
console.log('TOUCH MOVE AT:(X' + CONTROL.X + '),(' + CONTROL.Y + ')' );
//#############
if (CONTROL.MULTI_TOUCH == 'YES') {
var touches_changed = event.changedTouches;
for (var i=0; i<touches_changed.length;i++) {
//CONTROL.MULTI_TOUCH_X1
console.log("multi touch : x" + CONTROL.MULTI_TOUCH_INDEX + ":(" +touches_changed[i].pageX + ")");
switch(i)
{
case 1:
CONTROL.MULTI_TOUCH_X1=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y1=touches_changed[i].pageY;
break;
case 2:
CONTROL.MULTI_TOUCH_X2=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y2=touches_changed[i].pageY;
break;
case 3:
CONTROL.MULTI_TOUCH_X3=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y3=touches_changed[i].pageY;
break;
case 4:
CONTROL.MULTI_TOUCH_X4=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y4=touches_changed[i].pageY;
break;
case 5:
CONTROL.MULTI_TOUCH_X5=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y5=touches_changed[i].pageY;
break;
case 6:
CONTROL.MULTI_TOUCH_X6=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y6=touches_changed[i].pageY;
break;
case 7:
CONTROL.MULTI_TOUCH_X7=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y7=touches_changed[i].pageY;
break;
case 8:
CONTROL.MULTI_TOUCH_X8=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y8=touches_changed[i].pageY;
break;
case 9:
CONTROL.MULTI_TOUCH_X9=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y9=touches_changed[i].pageY;
break;
case 10:
CONTROL.MULTI_TOUCH_X10=touches_changed[i].pageX;
CONTROL.MULTI_TOUCH_Y10=touches_changed[i].pageY;
break;
default:
//code to be executed if n is different from case 1 and 2
}
}}
//#############
event.preventDefault();
},false);
////////////////////////////////////////////////////////
document.addEventListener('touchend', function(event)
{
CONTROL.LAST_X_POSITION = CONTROL.X;
CONTROL.LAST_Y_POSITION = CONTROL.Y;
CONTROL.MULTI_TOUCH = 'NO';
CONTROL.MULTI_TOUCH_INDEX = 1;
CONTROL.MULTI_TOUCH_X1 = null;
CONTROL.MULTI_TOUCH_X2 = null;
CONTROL.MULTI_TOUCH_X3 = null;
CONTROL.MULTI_TOUCH_X4 = null;
CONTROL.MULTI_TOUCH_X5 = null;
CONTROL.MULTI_TOUCH_X6 = null;
CONTROL.MULTI_TOUCH_X7 = null;
CONTROL.MULTI_TOUCH_X8 = null;
CONTROL.MULTI_TOUCH_X9 = null;
CONTROL.MULTI_TOUCH_X10 = null;
CONTROL.MULTI_TOUCH_Y1 = null;
CONTROL.MULTI_TOUCH_Y2 = null;
CONTROL.MULTI_TOUCH_Y3 = null;
CONTROL.MULTI_TOUCH_Y4 = null;
CONTROL.MULTI_TOUCH_Y5 = null;
CONTROL.MULTI_TOUCH_Y6 = null;
CONTROL.MULTI_TOUCH_Y7 = null;
CONTROL.MULTI_TOUCH_Y8 = null;
CONTROL.MULTI_TOUCH_Y9 = null;
CONTROL.MULTI_TOUCH_Y10 = null;
console.log('LAST TOUCH POSITION AT:(X' + CONTROL.X + '),(' + CONTROL.Y + ')' );
},false);
////////////////////////////////////////////////////////
document.addEventListener("touchcancel", function(event)
{
console.log('BREAK - LAST TOUCH POSITION AT:(X' + CONTROL.X + '(,(' + CONTROL.Y + ')' );
}, false);
////////////////////////////////////////////////////////
