HTML5 Canvas Keyboard events with Konva

HTML5 Canvas Keyboard events with Konva

There are no build-in keyboards events like keydown or keyup in Konva.

But how to listen keydown or keyup events on canvas?

You can easily add them by two ways:

  1. Listen global events on window object
  2. Or make stage container focusable with tabIndex property and listen events on it.

Instructions: click on stage to focus it, move a shape with arrows

HTML5 Canvas Keyboard eventsview raw
<!DOCTYPE html>
<html>

<head>
<script src="https://unpkg.com/konva@2.4.2/konva.min.js"></script>
<meta charset="utf-8">
<title>Canvas Keyboard events Demo</title>
<style>
body {
margin: 0;
padding: 0;
overflow: hidden;
background-color: #F0F0F0;
}
</style>
</head>

<body>
<div id="container"></div>
<script>
var stage = new Konva.Stage({
container: 'container',
width: window.innerWidth,
height: window.innerHeight
});

var layer = new Konva.Layer();
stage.add(layer);

var circle = new Konva.Circle({
x: stage.getWidth() / 2,
y: stage.getHeight() / 2 + 10,
radius: 70,
fill: 'red',
stroke: 'black',
strokeWidth: 4
});

layer.add(circle);
layer.draw();


var container = stage.container();

// make it focusable

container.tabIndex = 1;
// focus it
// also stage will be in focus on its click
container.focus();


const DELTA = 4;

container.addEventListener('keydown', function (e) {
if (e.keyCode === 37) {
circle.x(circle.x() - DELTA);
} else if (e.keyCode === 38) {
circle.y(circle.y() - DELTA);
} else if (e.keyCode === 39) {
circle.x(circle.x() + DELTA);
} else if (e.keyCode === 40) {
circle.y(circle.y() + DELTA);
} else {
return;
}
e.preventDefault();
layer.batchDraw();
});
</script>

</body>

</html>