How to create new zoom buttons in Open Layers?

Question

I have created two buttons (using Bootstrap) for zooming in and out:

<div class="btn-toolbar" id="buttontoolbar">
    <div id="newSim", class="btn-group-vertical">
        <button type="button" title="Zoom in", class="btn btn-default",id="olZoomOutLink"><img src="plus.svg"></button>
        <button type="button" title="Zoom out", class="btn btn-default", id="customZoomOut"><img src="minus.svg"></button>
    </div>
</div>

I have also turned off the default zoom buttons for Open Layers:

var map = new ol.Map({
    controls: ol.control.defaults({
        zoom: false,
    })
})

Now my question is, how can I make my two buttons work for zoom-in and zoom-out?

Thanks!

Answer 1

After creating your html buttons in the html file, then you add a control on each one by referring the id from the html. After that listen to the click event on the map.

var zoomType;
document.getElementById('customZoomOut').onclick = function() {
    zoomType="customZoomOut";
};
document.getElementById('olZoomOutLink').onclick = function() {
    zoomType="olZoomOutLink";
};

var map = new ol.Map({
    target: 'map',
    layers: [new ol.layer.Tile({ source: new ol.source.OSM() })],
    view: new ol.View({ center: [0, 0], zoom: 2 })
});

map.on('click', function(evt) {
    if(zoomType=="olZoomOutLink"){
         var view = map.getView();
         var zoom = view.getZoom();
         view.setZoom(zoom - 1);
    }
    if(zoomType=="customZoomOut"){
         var view = map.getView();
         var zoom = view.getZoom();
         view.setZoom(zoom + 1);
    }
});

<link rel="stylesheet" href="https://openlayers.org/en/v4.6.4/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/v4.6.4/build/ol.js"></script>

<div class="btn-toolbar" id="buttontoolbar">
  <div id="newSim" , class="btn-group-vertical">
    <button type="button" title="Zoom in" class="btn btn-default" id="olZoomOutLink"><img src="plus.svg"></button>
    <button type="button" title="Zoom out" class="btn btn-default" id="customZoomOut"><img src="minus.svg"></button>
  </div>
</div>