Question

I am trying to download xml files from server when my application starts. So i want to show splash screen until am done with downloading and then show next screen. below is my code:

Here, i want to show My splash screen when getTopNotDoc() method is under execution. and after completion of that method show next screen.

//get _topics and notification document<br>
_getDoc = new ServerConnectivity(this);

public class ServerConnectivity {

private Document _questionDoc;
private Document _topics;
private Document _notifications;

public ServerConnectivity(ApplicationSession appSession){
    //getTopNotDoc();
    _this = this;
    _appSession = appSession;
            new Thread(new Runnable(){
               public void run(){   
           getTopNotDoc();
               }
            }).start();
    }
}


private void getTopNotDoc(){
    InputStream inputStream = null ;
    try{
        // Build a document based on the XML file.
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();

        inputStream = getClass().getResourceAsStream("topics.xml");
        _topics = builder.parse( inputStream );
        inputStream = getClass().getResourceAsStream("notification.xml");
        _notifications = builder.parse( inputStream ); 

        if(_topics == null || _notifications == null){
                Dialog.alert("Unable to connect to internet");
        }
    } 
    catch ( Exception e ){
        System.out.println( e.toString() );
    }
    finally{
        if(inputStream != null){
            try {
                inputStream.close();
            } 
            catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Answer 1

To add some flexibility and keep your classes loosely coupled together, you could make some modifications to your ServerConnectivity class so your calls could go something like the following:

// push your splash screen on to the stack
//
final SplashScreen splashScreen = new SplashScreen();
UiApplication.getUiApplication().pushScreen(splashScreen);

_getDoc = new ServerConnectivity(this, new ServerConnectivityListener() {
    public void onCompleted(ServerConnectivity sender) {

        // display next screen
        //
        UiApplication.getUiApplication().invokeLater(new Runnable() {
            public void run() {
                splashScreen.close();
                UiApplication.getUiApplication().pushScreen(new NextScreen());
            }
        });
    }

    public void onError(ServerConnectivity sender) {
        splashScreen.close();
        // display error message, retry, etc...
    }
 });

For this to work, you need an interface with the following definition:

public interface ServerConnectivityListener {
    void onCompleted(ServerConnectivity sender);
    void onError(ServerConnectivity sender);
}

So, your ServerConnectivity class maintains a reference to some object that implements the interface called ServerConnectivityListener This allows you to maintain loose coupling between the subject class and any observers that need to listen for events.

Within ServerConnectivity, you would make calls to the listener’s methods something like this:

// begin excerpt from above...
//
if(_topics == null || _notifications == null) {
     _listener.onError(this);
} else {
    _listener.onCompleted(this);
}
catch ( Exception e ){
    System.out.println( e.toString() );
    _listener.onError(this);
//
// end excerpt from above...