Implementing additional features

InputScreen

The InputScreen class is an additional class for text input. It is launched from the FileSelector class in situations where a new folder is created or a file renamed.

The InputScreen class contains a TextField and standard OK / CANCEL Commands. The entered text is returned to the FileSelector as the new file or folder name.

To implement InputScreen class:

1. Create the InputScreen.java class file.

2. Import the required packages and classes.

   import javax.microedition.lcdui.*;

3. Set InputScreen to extend Form and implement CommandListener. Create the Commands and other variables.

   class InputScreen extends Form implements CommandListener {
   
       private final ImageViewerMIDlet midlet;
       private final TextField inputField =
               new TextField("Input", "", 32, TextField.ANY);
       private final Command okCommand =
               new Command("OK", Command.OK, 1);
       private final Command cancelCommand =
               new Command("Cancel", Command.OK, 1);

4. Make the InputScreen available in the MIDlet main view.

       InputScreen(ImageViewerMIDlet midlet) {
           super("Input");
           this.midlet = midlet;
           append(inputField);
           addCommand(okCommand);
           addCommand(cancelCommand);
           setCommandListener(this);
       }

5. Create methods for setting up the TextField and to read the text String.

       public void setQuestion(String question, String text) {
           inputField.setLabel(question);
           inputField.setString(text);
       }
   
       public String getInputText() {
           return inputField.getString();
       }

6. Implement the commandAction method.

       public void commandAction(Command command, Displayable d) {
           if (command == okCommand) {
               midlet.input(inputField.getString());
           } else if (command == cancelCommand) {
               midlet.cancelInput();
           }
       }
   }

ErrorScreen

The ErrorScreen class creates an Alert of type ERROR, which is shown in situations where the MIDlet cannot, for example, access a certain directory. The exact message String is entered in the showError method.

To implement the ErrorScreen class:

1. Create the ErrorScreen.java class file.

2. Import the required packages and classes.

   import javax.microedition.lcdui.*;

3. Set ErrorScreen to extend Alert. Create the required variables.

   class ErrorScreen
           extends Alert {
   
       private static Image image;
       private static Display display;
       private static ErrorScreen instance = null;

4. Define the Alert properties and create a method for displaying it.

       private ErrorScreen() {
           super("Error");
           setType(AlertType.ERROR);
           setTimeout(5000);
           setImage(image);
       }
   
       static void init(Image img, Display disp) {
           image = img;
           display = disp;
       }
   
       static void showError(String message, Displayable next) {
           if (instance == null) {
               instance = new ErrorScreen();
           }
           instance.setTitle("Error");
           instance.setString(message);
           display.setCurrent(instance, next);
       }
   }