How can I send data from swift to javascript and display them in my web view?
I am doing an iOS hybrid app using swift 2 and HTML/Javascript. I have a native shell which get some information from the calendar and the GPS. I would like to display those information in my WKWebView and update them every seconds. I am working with local HTML.
I have found some example showing how to communicate between the native code and the JS but nothing on how to transfer my "native" datas and display them in the web view. Thanks.
Answer
You should ask the Location Manager to update the location for you instead of setting up a 1-second NSTimer to do it yourself. And to pass data to Javascript, you can use evaluateJavaScript method of WKWebView:
import UIKit
import WebKit
import CoreLocation
class ViewController: UIViewController, CLLocationManagerDelegate {
weak var webView: WKWebView!
let locationManager = CLLocationManager()
override func viewDidLoad() {
super.viewDidLoad()
createWebView()
locationManager.delegate = self
locationManager.startUpdatingLocation()
locationManager.requestWhenInUseAuthorization()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func createWebView() {
let url = NSBundle.mainBundle().URLForResource("my_page", withExtension: "html")!
let webView = WKWebView()
webView.loadFileURL(url, allowingReadAccessToURL: url)
webView.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(webView)
// Auto Layout
let views = ["webView": webView]
let c1 = NSLayoutConstraint.constraintsWithVisualFormat("H:|[webView]|", options: [], metrics: nil, views: views)
let c2 = NSLayoutConstraint.constraintsWithVisualFormat("V:[webView]|", options: [], metrics: nil, views: views)
let c3 = NSLayoutConstraint(item: webView, attribute: .Top, relatedBy: .Equal, toItem: self.topLayoutGuide , attribute: .Bottom, multiplier: 1, constant: 0)
NSLayoutConstraint.activateConstraints(c1 + c2 + [c3])
// Pass the reference to the View's Controller
self.webView = webView
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let lastLocation = locations.last!
let dict = [
"lat": lastLocation.coordinate.latitude,
"long": lastLocation.coordinate.longitude
]
let jsonData = try! NSJSONSerialization.dataWithJSONObject(dict, options: [])
let jsonString = String(data: jsonData, encoding: NSUTF8StringEncoding)!
// Send the location update to the page
self.webView.evaluateJavaScript("updateLocation(\(jsonString))") { result, error in
guard error == nil else {
print(error)
return
}
}
}
}
And my_page.html:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8">
<meta name="viewport" content="width=device-width; initial-scale=1.0">
<title>This is a test page</title>
<script type="text/javascript">
function updateLocation(data)
{
var ele = document.getElementById('location');
ele.innerHTML = 'Last location: lat = ' + data['lat'] + ', long = ' + data['long'];
}
</script>
</head>
<body>
<p id="location">Last location:</p>
</body>
</html>
If you are testing this in the Simulator, choose Debug > Location > City Run to see it update continuously (as if you are running through a park).