PV239 #android2
cv2
Marek Sedlak
@msed__
YOU WANT TO SCROLL?
LISTVIEW
ListView
● A view that shows items in a vertically scrolling list.
● Typical use case is phonebook
● Model -> Adapter -> ViewHolder
ListView.setAdapter(adapter);
● More efficient -> RecyclerView (more complicated; try at home)
NETWORKING
Networking
● AndroidManifest.xml
○ <uses-permission android:name="android.permission.INTERNET" />
● Images
○ Glide / Picasso / Fresco
● Http
○ OkHttpClient
○ HttpUrlConnection
● REST
○ Retrofit 2
● JSON
○ GSON
Glide / Picasso / Fresco
● Nice overview
○ http://stackoverflow.com/questions/29363321/picasso-v-s-imageloader-v-s-
fresco-vs-glide
● We use Glide
○ https://github.com/bumptech/glide#download
○ https://github.com/bumptech/glide#how-do-i-use-glide
● Glide.with(this).load("http://goo.gl/gEgYUd").into(imageView);
● Nice tutorials
○ https://futurestud.io/tutorials/glide-image-resizing-scaling
EXERCISE1
Playing with images.
Show Item in the Listview with 120x120 resolution
● Add Glide into Gradle file
● Add ImageView into item layout
● Then
● Glide
.with(context)
.load(url)
.override(120, 120)
.fitCenter()
.into(imageView);
Gson
● Java serialization/deserialization Library by Google
● https://mvnrepository.com/artifact/com.google.code.gson/gson
● Let’s say
public class User {
public String name; // + getter, setter
}
● Then
Gson gson = new Gson();
User user = new User(); user.setName(“Fero”);
String userJson = gson.toJson(user);
User userCopy = gson.fromJson(userJson, User.class)
OkHttpClient
● An HTTP & HTTP/2 client for Android and Java applications
● http://square.github.io/okhttp/
● https://mvnrepository.com/artifact/com.squareup.okhttp3/okhttp
● Nice example from Android1 slides:
Request request = new Request.Builder()
.url(url)
.post(RequestBody.create(.., json))
.build();
Response response = client
.newCall(request)
.execute();
response.body().string();
Retrofit2 - once you hear REST, use this
● A type-safe HTTP client for Android and Java
● https://square.github.io/retrofit/
● https://mvnrepository.com/artifact/com.squareup.retrofit2/retrofit
public interface GitHubService {
@GET("users/{user}/repos")
Call<List<Repo>> listRepos(@Path("user") String user);
}
Retrofit retrofit = new Retrofit.Builder()
.baseUrl("https://api.github.com/")
.build();
GitHubService service = retrofit.create(GitHubService.class);
Call<List<Repo>> repoListCall = service.listRepos("octocat");
repoListCall.enqueue(...);
EXERCISE2
Playing with REST.
Show avatar from Github username in the ImageView
● API Docs: https://developer.github.com/v3
○ https://developer.github.com/v3/users/#get-a-single-user
● GSON
● Glide
● Retrofit2
THANK YOU
See you on Slack.