NSC AD 340 5210 - Week 7

Lecture Recording: https://youtu.be/JGEsLpC6IU4

1. Week 7 Lecture Making Network Requests & Loading Images
2. What are we building this week? Loading remote data from OpenWeatherMap api 02 Project Demo Making Network Requests 01 Loading Remote Images Loading remote images from a URL 03
3. Project Demo What are we building this week?
4. Week 7 Project Updates • Load current forecast data from OpenWeatherApi • Load 7-day forecast data from OpenWeatherApi • Load and display forecast icons from a remote URL
5. Making Network Requests Loading remove data from OpenWeatherMap api
6. How do we load data from a remote source?
7. Retrofit • HTTP client for Android & Java • Open-source library from Square
8. Retrofit Remote Data Source Request Response
9. Retrofit Remote Data Source Request Response Retrofit
10. Api Interface Define your HTTP api using a Kotlin/Java interface Retrofit.Builder The Retrofit.Builder class will help generate an implementation of your api service Call The Call class lets you make synchronous & asynchronous requests to your api Retrofit
11. Define Your API Interface data class Forecast(val temp: Float) data class Coordinates(val lat: Float, val lon: Float) /** * Api response for OpenWeatherMap's /weather endpoint */ data class CurrentWeather( val name: String, val coord: Coordinates, @field:Json(name = "main") val forecast: Forecast )
12. Define Your API Interface /** * http://api.openweathermap.org/data/2.5/weather?zip=98119&units=imperial&appid=<apikey> */ @GET("/data/2.5/weather") fun currentWeather( @Query("zip") zipcode: String, @Query("appid") apiKey: String, @Query("units") units: String ) : Call<CurrentWeather>
13. Create Your API Implementation val retrofit = Retrofit.Builder() .baseUrl("http://api.openweathermap.org") .addConverterFactory(MoshiConverterFactory.create()) .build() return retrofit.create(OpenWeatherMapService::class.java)
14. Create Your API Implementation val call = weatherService.currentWeather(zipcode, “some api key”, "imperial") call.enqueue(object : Callback<CurrentWeather> { override fun onFailure(call: Call<CurrentWeather>, t: Throwable) { Log.e(ForecastRepository::class.java.simpleName, "error loading current weather", t) } override fun onResponse(call: Call<CurrentWeather>, response: Response<CurrentWeather>) { val weatherResponse = response.body() if (weatherResponse != null) { // handle the loaded weather } } })
15. Threading On Android
16. • A Thread is an independent path of execution within your code • Instructions are run 1 by 1 • An instruction can’t start until the previous one is finished; in this case, the 2nd instruction is “blocked” by the first Threading On Android
17. • Android apps run on the Main Thread by default • Every 16ms the UI will draw itself • Block the Main Thread, and you will cause slowdowns and jank in your UI • Block the Main Thread for too long, and you’ll receive an “Activity Not Responding” dialog Threading On Android
18. • To avoid blocking the Main Thread, long running tasks should be run on a background thread • Threads, Executors, Runnables, AsyncTask, RxJava, Coroutines, Work Manager - a lot of ways to do background work • We will use Retrofit for this week’s assignment Threading On Android
19. • The Retrofit Call class enables us to asynchronously load data • Pass a Callback to be notified when your request is complete • The work will be done on a background thread and you will be notified on the Main Thread Retrofit Call Callbacks
20. Create Your API Implementation val call = weatherService.currentWeather(zipcode, “some api key”, "imperial") call.enqueue(object : Callback<CurrentWeather> { override fun onFailure(call: Call<CurrentWeather>, t: Throwable) { Log.e(ForecastRepository::class.java.simpleName, "error loading current weather", t) } override fun onResponse(call: Call<CurrentWeather>, response: Response<CurrentWeather>) { val weatherResponse = response.body() if (weatherResponse != null) { // handle the loaded weather } } })
21. OpenWeatherMap Api Load dynamic weather data
23. • https://openweathermap.org/api • /weather - returns current weather • /onecall - returns many things including 7-day forecast OpenWeatherMap API
24. Loading Remote Images Loading remote images from a URL
25. • App resources can’t all be packaged with an app • Images/Video/Music/etc must be loaded from the network • Multiple libraries available to load remote images in our app Loading Remote Images
26. • Glide • Picasso • Coil Image Loading Libraries
27. Loading An Image With Coil imageView.load("<image url>")
28. Demo