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Developing Second Screen Apps for Google TV

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Carmen Delessio shows you how to develop second screen apps for Google TV, including how to fling a URL, how to send KeyEvents to the TV, and how to send mouse events to the TV.

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In Hour 22, “Examining an Example Second Screen App,” you installed the example Blackjack second screen app. In doing so, you downloaded and installed the Anymote Library and set up three Eclipse projects. Those projects were the Anymote Library, the remote control app, and the TV app.

In this hour, we will develop several second screen apps. The first app takes a URL entered on the remote device and opens the corresponding web page in the Chrome browser on Google TV. That represents a simple content app that pairs with the TV, but runs only on the remote. It provides an example of a basic remote app and uses the ability to fling an Android Intent to the TV. Apps for keyboard input and mouse events will also be developed. We’ll use the phone’s Accelerometer as the input device for sending mouse events to the TV. These example apps provide a foundation for creating more sophisticated second screen apps.

Flinging a URL

By installing and running the Blackjack second screen app in Hour 22, you added the Anymote Library to your Eclipse projects. We’ll use the Anymote Library and develop a remote app that takes a URL as input on an Android phone and opens the website on the Chrome browser on a Google TV. Because we can use an Android Intent to show the website on the TV, there is no need to create a separate TV app.

An App for Displaying Websites on a Google TV

We’ll start with an Android app that includes an EditText field for input and a button to initiate an action. We’ll make it a Google TV remote app by doing the following:

  • Adding the Anymote Library
  • Implementing the Activity as an AnymoteClientService ClientListener
  • Binding to the Anymote Service
  • Modifying the Android manifest to support the Anymote Library

All these things were done in the code for the Blackjack remote app, and we will use that as our model.

The input field for this app will accept a URL. The button in the activity reads the URL and attempts to send it to the TV. Figure 23.1 shows the remote user interface.

Figure 23.1

Figure 23.1. Send a URL to the Chrome Browser remotely.

The Anymote Library is added to the working Eclipse project, as it was in Hour 22.

For this app, we need only the remote app, and it will consist of a single Activity. Each remote app in this hour has a similar code structure:

  • An Activity that implements the AnymoteClientService ClientListener
  • A declaration of a ServiceConnection to bind to the Anymote Service
  • The Activity’s onCreate method that includes the binding to the Anymote Service
  • The implementation of the three methods required for ClientListener

Our Activity is called ExampleOneActivity. Similar to the BlackJackRemoteActivity, it is declared as follows:

public class ExampleOneActivity extends Activity implements ClientListener

Listing 23.1 shows the declaration of the Anymote sender and the service connection. A ServiceConnection is an Interface for monitoring the state of an application service. In our case, the service is the AnymoteClientService.

Listing 23.1. ServiceConnection Declaration

1: private AnymoteSender anymoteSender;
2: private ServiceConnection mConnection = new ServiceConnection() {
3:   public void onServiceConnected(ComponentName name, IBinder service) {
4:      mAnymoteClientService=((AnymoteClientService.AnymoteClientServiceBinder)
5:      service).getService();
6:      mAnymoteClientService.attachClientListener(ExampleOneActivity.this);
7:   }
8:   public void onServiceDisconnected(ComponentName name) {
9:      mAnymoteClientService.detachClientListener(ExampleOneActivity.this);
10:      mAnymoteClientService = null;
11:   }

In the onCreate method, we bind the AnymoteClientService to the Activity. The code to do that is shown next. An Intent is created using the activity and the AnymoteClientService class. A call to bindService binds the intent to the ServiceConnecton mService that we declared earlier. The flag BIND_AUTO_CREATE indicates that the service should be created.

Intent intent = new Intent(ExampleOneActivity.this,
bindService(intent, mConnection, Context.BIND_AUTO_CREATE);

Listing 23.2 shows the complete onCreate method for the Activity.

Listing 23.2. Remote Activity onCreate Method

1:  @Override
2:  public void onCreate(Bundle savedInstanceState) {
3:    super.onCreate(savedInstanceState);
4:    mContext = this;
5:    setContentView(R.layout.main);
6:    progressBar = (ProgressBar) findViewById(R.id.a_progressbar);
7:    progressBar.setVisibility(View.VISIBLE);
8:    Button go = (Button) findViewById(R.id.go);
9:    final EditText destination = (EditText) findViewById(R.id.destination);
10:   go.setOnClickListener(new OnClickListener() {
11:     @Override
12:     public void onClick(View v) {
13:       String url = destination.getText().toString();
14:       final Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
15:       anymoteSender.sendUrl (intent.toUri(Intent.URI_INTENT_SCHEME));
16:     }
17:   });
18:   handler = new Handler();
19:   Intent intent = new Intent(ExampleOneActivity.this, AnymoteClientService.class);
20:   bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
21: }

Lines 19 and 20 in Listing 23.2 show the binding of the AnymoteClientService to the Activity.

Lines 5 to 9 define the UI components. A ProgressBar is shown while pairing occurs. An EditText and Button are defined. A URL can be entered into the EditText. The Go Button initiates the action of displaying the URL on the TV. Figure 23.1 showed what these look like on the remote.

Lines 10 to 17 define the action that occurs when the Button is pressed. The value in the EditText field is read in line 13. In line 14, that value is used to create an Intent. Line 15 sends the Intent to the Google TV using the anymoteSender. The TV will launch the Chrome browser and display the page associated with the URL.

The work of the app is done in the onCreate method, but the setup of the AnymoteService and library is required to make it happen. Finally, the three methods required for the ClientListener must be implemented. Those are the onConnected, onDisconnected, and onConnectionFailed methods. They are shown in Listing 23.3. Because the Activity implements ClientListener, we can say that it is a ClientListener.

We are relying on the Anymote Library for the user interface for pairing. Our app controls the ProgressBar and provides the UI for navigating to a URL. Listing 23.3 shows that we hide the ProgressBar when the connection is made. The field anymoteSender is populated in the onConnected method on line 3.

Listing 23.3. Required Methods for ClientListener

1:   @Override
2:   public void onConnected(final AnymoteSender anymoteSender) {
3:     this.anymoteSender = anymoteSender;
4:     handler.post(new Runnable() {
5:       public void run() {
6:         progressBar.setVisibility(View.INVISIBLE);
7:       }
8:     });
9:   }
10:  @Override
11:  public void onDisconnected() {
12:    this.anymoteSender = null;
13:  }
14:  @Override
15:  public void onConnectionFailed() {
16:    System.out.println("connection failed");
17:  }

The onDestroy method for the Activity is used to clean up any outstanding resources when the Activity is destroyed. In Listing 23.4, we use the onDestroy method to detach and unbind the Anymote services from the current Activity.

Listing 23.4. Cleaning Up in the onDestroy Method

1:  @Override
2:  protected void onDestroy() {
3:    if (mAnymoteClientService != null) {
4:      mAnymoteClientService.detachClientListener(this);
5:    }
6:    unbindService(mConnection);
7:    super.onDestroy();
8:  }

The Anymote Library handles the UI for discovery and pairing. For this remote app, no companion TV app is required. The native functionality of flinging an Intent to the TV provides the functionality required.

An App for Showing a Facebook Image on a Google TV

We will create another second content app that flings a URL to the TV that is based on the work we did in Hour 18, “Developing a Complete App.” In that hour, we created a Google TV app that showed random images from a Facebook page. We will turn that app into a remote content app using the Anymote protocol. The phone will show a random image when a button is pressed. The TV will show the same image.

The onCreate method for the app shows how we make this happen. It is shown in Listing 23.5. The basic infrastructure of a remote app is followed. The Activity extends ClientListener and binds to the AnymoteClientService.

In the app in Hour 17, “Using Cursors and CursorLoaders,” we retrieved a list of photos from Facebook. We parsed the data and selected a random image to display. We select the random URL as a String in line 16 of Listing 23.5. We then use that URL for two things. We use an ImageViewFragment to display it on the phone and we use the Anymote Service to fling it to the TV as an Intent. The flinging occurs in lines 18 and 19.

Listing 23.5. Facebook Random Image Remote App

1:  @Override
2:  public void onCreate(Bundle savedInstanceState) {
3:    super.onCreate(savedInstanceState);
4:    setContentView(R.layout.main);
5:    LoadPhotos lp = new LoadPhotos("99394368305" );
6:    lp.execute();
7:    progressBar = (ProgressBar) findViewById(R.id.progressBar1);
8:    progressBar.setVisibility(View.VISIBLE);
9:    mButton2= (Button)findViewById(R.id.button2);
10:   mButton2.setEnabled(false);
11:   mButton2.setOnClickListener(new OnClickListener() {
12:     public void onClick(View v) {
13:       ImageViewFragment fbImg = new ImageViewFragment();
14:       Bundle args = new Bundle();
15:       int random = (int)(Math.random() * mPagePhotos.size());
16:       String url = mPagePhotos.get(random).source;
17:       args.putString("URL", url);
18:       final Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
19:       anymoteSender.sendUrl (intent.toUri(Intent.URI_INTENT_SCHEME));
20:       fbImg.setArguments(args);
21:       FragmentTransaction ft = getFragmentManager().beginTransaction();
22:       ft.replace(R.id.linearLayout1, fbImg, "Image from Facebook");
23:       ft.commit();
24:     }
25:   });
26:   handler = new Handler();
27:   Intent intent = new Intent(ExampleTwoActivity.this, AnymoteClientService.class);
28:   bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
29: }

Both of the examples used simple interfaces on the remote device and displayed the resulting content on the TV. They show the basic use of flinging a URL to the TV for display in a Chrome browser. It is easy to envision more complex user interfaces that also result in a URL being displayed on the TV. For example, an app could allow a user to enter complex search criteria into a phone and have the result displayed on the TV.

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