Ionic 3 : cannot read property 'addEventListener' of null : Google Maps

[naveenvuppu]

iam getting this error some times … please help

code :

google.maps.event.addListenerOnce(this.infoWindow, ‘domready’, () => {
document.getElementById(‘showDirections’).addEventListener(‘click’, () => {
//alert(‘Clicked’);
this.navCtrl.push(DirectionsMapsPage, {
latde: latde,
longtde: longtde
});
});
});