There are many ways of making custom OpenLayers controls, it seems that all the controls should extends the base control ol.control.Control.
Solution 1
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Simple Custom Control</title>
<!-- Bootstrap -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css">
<link rel="stylesheet" href="./ol.css" />
<!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/libs/html5shiv/3.7.2/html5shiv.js"></script>
<script src="https://oss.maxcdn.com/libs/respond.js/1.4.2/respond.min.js"></script>
<![endif]-->
<style>
.rotate-north{
top:80px;
left:.5em;
}
</style>
</head>
<body>
<div id="map" class="map"> </div>
<!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<!-- Include all compiled plugins (below), or include individual files as needed -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
<script src="./ol.js"></script>
<script>
var map = new ol.Map({
layers:[
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
target: 'map',
view: new ol.View({
center: [0,0],
zoom:2,
rotation: 1
})
});
var button = document.createElement('button');
button.innerHTML='N';
var handleRotationNorth = function(e){
map.getView().setRotation(0);
}
button.addEventListener('click',handleRotationNorth,false);
var element = document.createElement('div')
element.className="rotate-north ol-unselectable ol-control";
element.appendChild(button);
var RotationNorthControl = new ol.control.Control({
element: element
})
map.addControl(RotationNorthControl);
</script>
</body>
</html>
Solution 2
<!DOCTYPE html>
<html>
<head>
<title>Custom Controls</title>
<link rel="stylesheet" href="https://openlayers.org/en/v4.0.1/css/ol.css" type="text/css">
<!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
<script src="https://openlayers.org/en/v4.0.1/build/ol.js"></script>
<style>
.rotate-north {
top: 65px;
left: .5em;
}
.ol-touch .rotate-north {
top: 80px;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<script>
/**
* Define a namespace for the application.
*/
window.app = {};
var app = window.app;
//
// Define rotate to north control.
//
/**
* @constructor
* @extends {ol.control.Control}
* @param {Object=} opt_options Control options.
*/
app.RotateNorthControl = function(opt_options) {
var options = opt_options || {};
var button = document.createElement('button');
button.innerHTML = 'N';
var this_ = this;
var handleRotateNorth = function() {
this_.getMap().getView().setRotation(0);
};
button.addEventListener('click', handleRotateNorth, false);
button.addEventListener('touchstart', handleRotateNorth, false);
var element = document.createElement('div');
element.className = 'rotate-north ol-unselectable ol-control';
element.appendChild(button);
ol.control.Control.call(this, {
element: element,
target: options.target
});
};
ol.inherits(app.RotateNorthControl, ol.control.Control);
//
// Create map, giving it a rotate to north control.
//
var map = new ol.Map({
controls: ol.control.defaults({
attributionOptions: /** @type {olx.control.AttributionOptions} */ ({
collapsible: false
})
}).extend([
new app.RotateNorthControl()
]),
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
target: 'map',
view: new ol.View({
center: [0, 0],
zoom: 3,
rotation: 1
})
});
</script>
</body>
</html>