Lecture Mobile Application Development (119310)

iOS Development - Framework Basics Part III

Agenda

• More WebKit
  • WKWebView
• AV Foundation
  • MPMediaQuery
• Assignment Artist Explorer

WKWebView successor of UIWebView

App Transport Security

• Since version 9 of iOS it is required for any app to use only encrypted connections when accessing a web service
• Thus you should always use https://
• If this is not possible you can allow arbitrary loads in the apps plist file as shown here:

WKNavigationDelegate

• WKWebView will load URLs asynchronously
• In order to know, when the loading of a webpage started, finished and if a error occurred you can implement the WKNavigationDelegate protocol and register it with the WKWebView by e.g.: webView.navigationDelegate = self
• Implement the following methods in your view:

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    //Called when the navigation is complete.
}

func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
    //Called when web content begins to load in a web view.
}

func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
    //Called when an error occurs during navigation.    
}

UIApplication

• The UIApplication class provides a centralized point of control for your app. There is exactly one instance of it for each app (It’s a singleton). You can access it via the property shared of the UIApplication class.
• It routes user events
• It maintains a list of windows (UIViews)
• You can use it to access different settings, e.g. the Network Access Indicator

Network Access Indicator

• Loading of a webpage can take a while, thus you need to show the user that you are loading something
• This can be done by activating the Network Access Indicator using the UIApplication instance

UIApplication.shared.isNetworkActivityIndicatorVisible = true

MPMediaQuery

• The MPMediaQuery class allows you to query your iPod Library on the device - similar to Androids MediaStore (Content Provider)
• It is very simple to use, e.g. to retrieve all artists from your device:

let query = MPMediaQuery()

guard let items = query.items else {
    debugPrint("Error: query has no items object")
	return
}

if items.count == 0 {
    debugPrint("Error: no items found")
	return
}

for item in query.items! {
    if let artist = item.value(forProperty: MPMediaItemPropertyArtist)  {
        artists.append(artist as! String)
    }
}

MPMediaItem

• A MediaItem represents a single piece of media (song, video) in the iPod Library
• It has an ID and different properties that can be queried using the value(forProperty: ) method (or since Swift 3.0) directly accessed, e.g.:

if let artist = item.artist {
    print("Artist: \(artist)")
}

• To use it, import MediaPlayer in you ViewController class

import MediaPlayer

Medialibrary request authorisation

• Since iOS 9.3 it is required to request access to the MediaLibrary in order to read data. Do this by calling the requestAuthorization() method, e.g.

MPMediaLibrary.requestAuthorization { (status) in
    if status == .authorized {
        self.readMediaLibrary()
    } else {
        self.showError()
    }
}

Medialibrary Authorisation Status

• To check the authorisation status use the authorizationStatus() method, e.g.:

var error: String
switch MPMediaLibrary.authorizationStatus() {
    case .restricted:
        error = "Media library access restricted by corporate or parental settiongs"
    case .denied:
        error = "Media library access denied by user"
    default:
        error = "Unkown error"
}

Medialibrary User Information

• When access to the MediaLibrary is requested, the user will be prompted by iOS with a message. It is required that the developer adds an information text to the Info.plist, that explains the user why it should authorise access either your app could be rejected by Apple.
• Add the key NSAppleMusicUsageDescription to your info.plist

• Unfortunately it is not possible 
to access the Media Library in the simulator, it is not supported. You need a real device for this

Artist Explorer Assignment

• Please conduct the Artist Explorer Assignment and implement your own iOS Artist Explorer App

References

• Media Player: https://developer.apple.com/documentation/mediaplayer
• Use MusicKit to Add Music Playback: https://developer.apple.com/musickit/