Openlayers 3. How to make tootlip for feature

问题

Now I'm moving my project from openlayers 2 to openlayers 3. Unfortunately I can't find how to show title (tooltip) for feature. In OL2 there was a style named graphicTitle. Could you give me advice how to implement tooltip on OL3?

回答1:

This is example from ol3 developers. jsfiddle.net/uarf1888/

var tooltip = document.getElementById('tooltip');
var overlay = new ol.Overlay({
  element: tooltip,
  offset: [10, 0],
  positioning: 'bottom-left'
});
map.addOverlay(overlay);

function displayTooltip(evt) {
  var pixel = evt.pixel;
  var feature = map.forEachFeatureAtPixel(pixel, function(feature) {
    return feature;
  });
  tooltip.style.display = feature ? '' : 'none';
  if (feature) {
    overlay.setPosition(evt.coordinate);
    tooltip.innerHTML = feature.get('name');
  }
};

map.on('pointermove', displayTooltip);

回答2:

Here's the Icon Symobolizer example from the openlayers website. It shows how to have a popup when you click on an icon feature. The same principle applies to any kind of feature. This is what I used as an example when I did mine.

来源：https://stackoverflow.com/questions/35848697/openlayers-3-how-to-make-tootlip-for-feature