F09: Maps! Og litt mer HTTP
Android, Google Maps, AsyncTask, HTTP, Gson
Google Maps!
https://developers.google.com/maps/documentation/android-api/
En del features
- Markers
- GPS location
- Kart!
Get started!
API key???
Følg lenka i kommentaren i ^
Gir tilgang til Maps & identifiserer
API key 2
MapsActivity (generated)
MapsActivity (generated)
MapsActivity
- Finds the Map fragment
- Loads the map
- Creates a LatLng object
- Adds a Marker
(MarkerOptions)
- Moves the camera (CameraUpdateFactory)
Layout: activity_maps.xml
Google Play Services though
Location data: GPS!
- "Unikt" for apps
- Lar deg se brukerens lokasjon (innenfor en viss radius)
- To "grader" (trenger én permission):
- ACCESS_COARSE_LOCATION: WiFi + mobildata
- ACCESS_FINE_LOCATION: GPS + WiFi + mobildata
My Location layer
… men husk å sjekke permission
Thanks, GenyMotion
Mock locations with the emulator
Threads!
- Én tråd i Android!
- Kræsjer den, kræsjer appen
- Trege operasjoner fryser UI
Utfordringer med threads
- Kommunikasjon på tvers
- Kun UI-tråden kan "røre" UI
- Dermed:
- Start oppgaven
- (loop) Rapporter progress til UI thread
- Rapporter resultat til UI thread
Android: AsyncTask
- Magic?
- Har et ThreadFactory
- Som kaller
new Thread(...)
- Som kaller
new AsyncTask<Params, Progress, Result>() {
@Override
protected void onPreExecute() {
// Stuff to do on UI thread before starting
}
@Override
protected <Result> doInBackground(
<Params>... params
) {
// Perform a long task, like an HTTP request
return <Result>;
}
@Override
protected void onPostExecute(
<Result> result
) {
// Stuff to do on UI thread after finishing
}
}Nettverk (HTTP)
Veldig vanlig case for apps:
- Start appen
- Hent data fra server
- Vis frem data
- (La bruker endre noe)
- (Send data tilbake til server)
HTTP request
GET /users HTTP/1.1
Host: localhost:8081
Accept: */*
(Other headers go here)
<no body><verb> <path> HTTP/<version>
<Headers>
<Body>
POST /users HTTP/1.1
Host: localhost:8081
Accept: */*
(Other headers go here)
{"username": "theneva"}HTTP er enkelt i Java!
HttpURLConnection connection = (HttpURLConnection)
new URL("http://a.page.xyz/whatever").openConnection();
InputStream in = connection.getInputStream();
Scanner scanner = new Scanner(in);
String body = "";
while (scanner.hasNextLine()) {
body += scanner.nextLine();
}
// body = data from server as Stringjava.net.*
… men må gjøres i egen Thread
public class JustGetSomethingActivity extends Activity {
private TextView resultTextView;
// onCreate sets ^^^, calls vvv
private void downloadAndDisplayData() {
new AsyncTask<Void, Void, String>() {
@Override
protected String doInBackground(final Void... params) {
try {
HttpURLConnection connection =
(HttpURLConnection) new URL("https://google.com").openConnection();
return inputStreamToString(connection.getInputStream()); // made up method
} catch (IOException e) {
throw new RuntimeException(e); // I'm lazy
}
}
@Override
protected void onPostExecute(final String result) {
super.onPostExecute(result);
resultTextView.setText(result); // update the TextView
}
}.execute();
}
}
(les: AsyncTask)
Permissions…
<uses-permission
android:name="android.permission.INTERNET"/>
- Bare permission til å BRUKE internett
- ACCESS_NETWORK_STATE for sjekk
- ACCESS_NETWORK_STATE for sjekk
- Ikke lenger nødvendig i Marshmallow
- … men husk å spørre om de andre
Også lett å sette headers
HttpURLConnection connection = (HttpURLConnection)
new URL("http://a.page.xyz/whatever").openConnection();
connection.setRequestProperty("X-Token", "blahblah");
InputStream in = connection.getInputStream();
// ...X-Token: blahblah
HTTP statuskoder (TK1100)
- 2xx = Dandy!
- 200 OK
- 201 Created
- 3xx = Redirect
- 301 Moved Permanently
- 301 Moved Permanently
-
4xx = You messed up
- 400 Bad Request
- 401 Unauthorized
- 404 Not Found
HTTP statuskoder (TK1100)
-
4xx = You messed up
- 400 Bad Request
- 401 Unauthorized
- 404 Not Found
HttpURLConnection kaster exception!
401, 404, 410 (Gone), 420 => FileNotFoundException
4xx: Hva gikk galt?
doInBackground: Kan wrappe kode og body i et objekt:
✓ JSON for data transfer
// Arrays
[0, 1, 2]
["Hello", "world"]
// Objects
{
"key": "value",
"anotherKey", "anotherValue"
}
// Object with array
{
"name": "Liam",
"modules": [
"Physics",
"Maths"
]
}
// Array of objects
[
{ "name": "Liam" },
{ "name": "Martin" }
]"Fun"facts:
- More lightweight than XML
-
JSON is valid JavaScript
-
Easy to parse for JavaScript
- No schemas
Gson
- Googles forsøk på JSON-lib
- Veldig enkelt å bruke
// build.gradle
dependencies {
// ...
compile 'com.google.code.gson:gson:2.6.2'
}// Serialization
Gson gson = new Gson();
gson.toJson(1); // ==> 1
gson.toJson("abcd"); // ==> "abcd"
// Deserialization
int one = gson.fromJson("1", int.class);
Integer one = gson.fromJson("1", Integer.class);
Long one = gson.fromJson("1", Long.class);
Boolean false = gson.fromJson("false", Boolean.class);Gson: liste av objekter
- java.lang.reflect <3
// Deserialization
Type collectionType = new TypeToken<Collection<Integer>>(){}.getType();
Collection<Integer> ints2 = gson.fromJson(json, collectionType);Innlevering 2
Ut på eventyr!
PG4600-15-09: Maps! og litt mer HTTP
By theneva
PG4600-15-09: Maps! og litt mer HTTP
Android, Google Maps, AsyncTask, HTTP, Gson
