UITextFieldShouldChange 被调用两次

Question

I want a MKMapView to blur if there is no entry in a text field by using UIVisualEffectsView over top of the map, i also want it to aniamte, Right now the shouldChangeCharactersInRange its getting called twice when someone starts typing and not at all when the user removes all text from the UITextField . Heres my code

import UIKit
import MapKit
import Parse

class HomeAddressViewController: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate, UITextFieldDelegate {

let locationManager = CLLocationManager()

@IBOutlet var activityIndicator: UIActivityIndicatorView!
@IBOutlet var homeAddressField: UITextField!
@IBOutlet var homeAddressMap: MKMapView!
@IBOutlet var blurryMap: UIVisualEffectView! = UIVisualEffectView()
override func viewDidLoad() {
    super.viewDidLoad()

    activityIndicator.hidden = true

    homeAddressField.delegate = self

    locationManager.delegate = self
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.requestWhenInUseAuthorization()
    locationManager.startUpdatingLocation()

    blurAndUnblurMap()


}
func blurAndUnblurMap() {
    if homeAddressField.text?.characters.count == 0 {
        UIView.animateWithDuration(1, animations: {
            self.blurryMap.effect = UIBlurEffect(style: .Light)
        })
    } else {
        UIView.animateWithDuration(0.5, animations: {
            self.blurryMap.effect = nil
        })
    }
}

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    blurAndUnblurMap()
    return true
}
}

Answer 1

Why don't you do this instead?

homeAddressField.addTarget(self, "someFunction:", forControlEvents: .EditingChanged)

Get text changes and act accordingly.