Implementing the splash screen

When the MIDlet starts, it displays a splash screen containing the application title, icon, and progress bar. The progress bar is used to indicate what is happening while loading the movie database. Since the loading process can take some time, the splash screen is used to show the user how the loading progresses. The MovieBooking class listens for messages from MovieDB and informs SplashScreen so that the progress bar can advance.

Figure: Splash screen

The splash screen uses various typed events and listener interfaces to deal with specialized events. For more information about eSWT API typed listeners, see the org.eclipse.swt.events package. For more information about eSWT API untyped listeners, see the Event class.

To implement the splash screen:

1. Create the SplashScreen.java class file.

2. Import the required classes.

   import java.io.InputStream;
   import java.io.IOException;
   import org.eclipse.ercp.swt.mobile.Command;
   import org.eclipse.swt.SWT;
   import org.eclipse.swt.events.SelectionEvent;
   import org.eclipse.swt.events.SelectionListener;
   import org.eclipse.swt.graphics.Image;
   import org.eclipse.swt.graphics.Point;
   import org.eclipse.swt.layout.FormAttachment;
   import org.eclipse.swt.layout.FormData;
   import org.eclipse.swt.layout.FormLayout;
   import org.eclipse.swt.layout.GridData;
   import org.eclipse.swt.widgets.Composite;
   import org.eclipse.swt.widgets.Label;
   import org.eclipse.swt.widgets.ProgressBar;
   import org.eclipse.swt.widgets.Shell;

3. Set SplashScreen to implement SelectionListener, and create the required variables.

   class SplashScreen implements SelectionListener {
   
       private Composite splashComposite;
       private Label progressLabel;
       private ProgressBar progressBar;
       private Command exitCommand;
       private MovieBooking main;
       private Image appImage;

4. Create a new secondary Shell.

       SplashScreen(MovieBooking main, Shell mainShell) {
           this.main = main;
   
           // Parent Composite of the splash screen widgets
           splashComposite = new Composite(mainShell, SWT.NONE);
   
           // splashComposite's size and location are controlled
           // by the GridLayout of the mainShell
           splashComposite.setLayoutData(
                   new GridData(SWT.FILL, SWT.FILL, true, true));
   
           // Load the application's image
           InputStream imageStream = this.getClass().getResourceAsStream("/res/splash.png");
           if (imageStream != null) {
               appImage = new Image(mainShell.getDisplay(), imageStream);
               try {
                   imageStream.close();
               } catch (IOException e) {
                   // ignore, in this case it is not relevant
               }
           }

   In the code above, the appImage = new Image(mainShell.getDisplay(), imageStream) code line uses the Image class to define image resources for the screen.

   Note that getDisplay is a Widget class method.

5. Create the widgets for the splash screen. The last widget is an unselectable user interface in the form of a ProgressBar. The minimum and maximum values for the receiver are set to 0 and 10 respectively.

           // Create the widgets
           Label titleLabel = new Label(splashComposite, SWT.CENTER);
           titleLabel.setText("MovieBooking");
   
           Label imageLabel = new Label(splashComposite, SWT.CENTER);
           if (appImage != null) {
               imageLabel.setImage(appImage);
           }
   
           progressLabel = new Label(splashComposite, SWT.CENTER);
           progressLabel.setText("Loading...");
   
           progressBar = new ProgressBar(splashComposite, SWT.CENTER);
           progressBar.setMaximum(10);
           progressBar.setMinimum(0);

6. Create a layout for the widgets.

   A layout controls the size and position of the widgets. This MIDlet uses a special Layout class called FormLayout, which controls the size and position of a composite Control. The FormLayout requires that FormData and FormAttachment are created for each child: FormData is used to define the attachments of the a Control, whereas FormAttachment can be used to define the left, top, right, and bottom edges of each child.

   The setLayoutData method is used to first place the image on the screen. After that the title label, progress bar, and progress label are positioned by aligning them with the image and each other.

           // Distribute the widgets using a FormLayout
           FormLayout layout = new FormLayout();
           splashComposite.setLayout(layout);
   
           // Set the image at the center
           FormData imageLabelData = new FormData();
           Point imageSize = imageLabel.computeSize(SWT.DEFAULT, SWT.DEFAULT);
           imageLabelData.top = new FormAttachment(50, -imageSize.y / 2);
           imageLabelData.left = new FormAttachment(50, -imageSize.x / 2);
           imageLabel.setLayoutData(imageLabelData);
   
           // Set title label above the image
           FormData titleLabelData = new FormData();
           titleLabelData.left = new FormAttachment(imageLabel, 0, SWT.CENTER);
           titleLabelData.bottom = new FormAttachment(imageLabel, 0, SWT.TOP);
           titleLabel.setLayoutData(titleLabelData);
   
           // Set the progress bar at the center, below the title label
           FormData progressBarData = new FormData();
           progressBarData.left = new FormAttachment(imageLabel, 0, SWT.CENTER);
           progressBarData.top = new FormAttachment(imageLabel);
           progressBar.setLayoutData(progressBarData);
   
           // Set the progress label below the progress bar
           FormData progressLabelData = new FormData();
           progressLabelData.left = new FormAttachment(imageLabel, 0, SWT.CENTER);
           progressLabelData.top = new FormAttachment(progressBar, 0, SWT.BOTTOM);
           progressLabel.setLayoutData(progressLabelData);

7. Create a new Command instance, and use the setText method to define the text to be displayed for the command. The command is associated with a typed listener called SelectionListener, which invokes the appropriate method after an event has been generated by the Control.

           // Add the exit command
           exitCommand = new Command(mainShell, Command.EXIT, 0);
           exitCommand.setText("Exit");
           exitCommand.addSelectionListener(this);
           exitCommand.setDefaultCommand();
       }
   
       public void widgetSelected(SelectionEvent e) {
           if (e.widget == exitCommand) {
               destroy();
               main.exit();
           }
       }
   
       public void widgetDefaultSelected(SelectionEvent e) {
       }

8. Create methods for interacting with the progress bar.

       // Set the text of the progress label
       void setLabel(String label) {
           if (!progressLabel.isDisposed()) {
               progressLabel.setText(label);
               splashComposite.layout();
           }
       }
   
       // Set how many movies will be displayed. In practice it changes the
       // range of the progress bar
       void setMoviesCount(int count) {
           if (!progressBar.isDisposed()) {
               progressBar.setMaximum(count);
           }
       }
   
       // Advance the progress bar
       void advance() {
           if (!progressBar.isDisposed()) {
               progressBar.setSelection(progressBar.getSelection() + 1);
           }
       }

9. Create a method for disposing of the splash screen.

       void destroy() {
           exitCommand.dispose();
           splashComposite.dispose();
           if (appImage != null) {
               appImage.dispose();
           }
       }
   }