Agenda

http://padc.github.io/gdg-devfest-2014

• Quick introduction to Android in general
  • Platform
  • Language
  • VM (Dalvik -> ART)
  • Play Store

• Developing apps for Android
  • Tools
  • Basic components
    • Activities
    • Fragments
    • Async Tasks
    • Services
    • Broadcast Receivers
  • Persistence

whoami

Evan Dale Aromin

• Software Engineer @ coins.ph
• Android / Python / JS
• Twitter, Github - @avendael
• avendael.com

what is android

• Aside from being a mobile device, it is a platform as well
• Platform is not only being used in phones
  • Glass
  • TV
  • Wear

android as a platform

• Java - JDK6, recently JDK7 support added
  • Trimmed down Java ie. no AWT, Swing, etc.
• Dalvik - Android's JVM equivalent
  • Designed for resource constrained devices
  • Uses Just In Time compilation ie. app compiled to bytecode upon launching

• ART - Android Runtime
  • Replacement to Dalvik for Lollipop above
  • Uses Ahead of Time compilation ie. app compiled to bytecode upon installing
  • Improvements to Garbage Collection, debugging, and profiling
  • Backwards compatible to Dalvik

• Google Play
  • Was historically called Android Market, a place to get apps from
  • Also a place for users to buy music, books, and videos
  • For some countries, it is also a place where users can avail of a device

Android Development

• Development tools
  • Either Eclipse or Android Studio
  • IntelliJ Ultimate also includes most of Android Studio features
  • Android SDK
  • Genymotion for emulation

Activities

• What the user primarily interacts with
• Apps are usually composed of multiple activities
• Application UI flow APIs
• Lifecycle hooks

• Lifecycle
  • onCreate - Activity being created
  • onStart - Activity about to become visible
  • onResume - User can now interact with the Activity
  • onPause - Another Activity is about to take focus
  • onStop - Activity is no longer visible
  • onDestroy - Activity is about to be destroyed

public class SplashActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<!-- main.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:gravity="center">
    <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello, World!"
            android:textSize="40sp"
            android:gravity="center"/>
</LinearLayout>

Fragments

• Portion of UI in an Activity
• Multiple Fragments can exist in one Activity
• Has its own lifecycle, but usually mirrors the Activity lifecycle

public class SplashActivity extends FragmentActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        getSupportFragmentManager()
                .beginTransaction()
                .replace(R.id.fl_fragment_container,
                    new SplashFragment(), "SplashFragment")
                .commit();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<!-- main.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent">
    <FrameLayout android:id="@+id/fl_fragment_container"
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"/>
</LinearLayout>

public class SplashFragment extends Fragment {
    @Override
    public View onCreateView(
                LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
        return inflater.inflate(R.splash_fragment, container, false);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<!-- splash_fragment.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:gravity="center">
    <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello, World!"
            android:textSize="40sp"
            android:gravity="center"/>
</LinearLayout>

AsyncTask

• Performs operations in the background
• Publish results in th UI thread
• Ideally for short operations

public class SplashActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        new AsyncTask<Void, Void, Void>() {

            @Override
            protected Void doInBackground(Void... params) {
                try {
                    // Busy work
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                return null;
            }

            @Override
            protected void onPostExecute(Void aVoid) {
                super.onPostExecute(aVoid);
                finish();
            }
        }.execute();
    }
}

Services

• Preferred for long running operations
• Does not have a UI
• Does not necessarily have to interact with an Activity
• Uses include, and are not limited to
  • Network calls
  • IO
  • Sending notifications

• Started Service
  • Much like a daemon
• Bound Service
  • IPC calls
• Intent Service
  • Does one thing, and then dies

public class SplashService extends IntentService {
    public SplashService() {
        super(TAG);
    }

    public SplashService(String name) {
        super(name);
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        Toast.makeText(this, "Hello, World!", Toast.LENGTH_LONG).show();
    }
}

Broadcast Receivers

• Receives a broadcast
  • From the system
  • From the app (LocalBroadcastManager)

public class SplashBroadcastReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(
                context,
                intent.getStringExtra("SplashServiceBroadcast"),
                Toast.LENGTH_LONG
        ).show();
    }
}

public class SplashService extends IntentService {
    // Constructors omitted
    @Override
    protected void onHandleIntent(Intent intent) {
        Intent broadcastIntent = new Intent("SplashBroadcast");

        broadcastIntent.putExtra("SplashServiceBroadcast", "Hello, World!");
        sendBroadcast(broadcastIntent);
    }
}

And More...

• These stuff warrant a Whirlwind Trip Part II™
  • SQLite
  • ContentProviders
  • SharedPreferences
  • Intents
  • ActionBar
  • Layouts and UI elements
  • Widgets

Putting it all together

https://github.com/padc/AllTogether

Thanks!