Implementing the MIDlet MainView class

To implement the MainView class:

1. Create the MainView.java class file.

2. Import the required packages and classes.

   package com.nokia.example.imagescaler;
   
   import java.io.IOException;
   
   import javax.microedition.lcdui.Alert;
   import javax.microedition.lcdui.AlertType;
   import javax.microedition.lcdui.Command;
   import javax.microedition.lcdui.CommandListener;
   import javax.microedition.lcdui.Display;
   import javax.microedition.lcdui.Displayable;
   import javax.microedition.lcdui.Form;
   import javax.microedition.lcdui.Image;
   import javax.microedition.lcdui.StringItem;
   
   import com.nokia.mid.ui.FileSelect;
   import com.nokia.mid.ui.FileSelectDetail;

3. Create the MainView class to extend Form and implement CommandListener.

   public class MainView
               extends Form
               implements CommandListener
   {

4. Create the required constants and variables.

   private static final String LOGO_IMAGE_URI = "/logo.png";
   private static final String INFO_TEXT =
       "This application helps you in downscaling the images using the Image "
       + "Scaling API.";
   private static final int ERROR_DIALOG_TIMEOUT = 5000;
   
   private final Command exitCommand = new Command("Exit", Command.EXIT, 1);
   private final Command browseImagesCommand = new Command("Browse images", Command.OK, 1);
   private Main main = null;
   private ImageCanvas imageCanvas = null;
   private Image logoImage = null;
   private StringItem stringItem = null;
   private String originalImageUrl = null;

5. Create the MainView class constructor. In the constructor, create the Image and the Commnad Buttons and add it to Screen.

   public MainView(String title, Main main) {
       super(title);
   
       this.main = main;
   
       try {
           logoImage = Image.createImage(LOGO_IMAGE_URI);
       }
       catch (IOException e) {
       }
   
       stringItem = new StringItem("About", INFO_TEXT);
       append(stringItem);
   
       addCommand(browseImagesCommand);
       addCommand(exitCommand);
       setCommandListener(this);
   
   }

6. Implement commandAction method from the CommandListener interface to capture UI events and handle them to call the respective functions calls.

   public void commandAction(Command command, Displayable displayable) {
       final MainView mainView = this;
   
       if (command == exitCommand) {
           main.quit();
       }
       else if (command == browseImagesCommand) {
           new Thread() {
               public void run() {
                   try {
                       FileSelectDetail selectedFiles[] =
                           FileSelect.launch(Utils.PHOTOS_DIR,
                                             FileSelect.MEDIA_TYPE_PICTURE,
                                             false);
   
                       if (selectedFiles != null && selectedFiles.length > 0) {
                           originalImageUrl = selectedFiles[0].url;
   
                           if (imageCanvas == null) {
                               imageCanvas = new ImageCanvas(mainView);
                           }
   
                           if (imageCanvas.loadImage(originalImageUrl) == true) {
                               Display.getDisplay(main).setCurrent(imageCanvas);
                           }
                       }
                   }
                   catch (Exception e) {
                   }
               }
           }.start();
       }
   }

7. Create displayThis method, to show this (MainView) view on the Screen.

   public void displayThis() {
       Display.getDisplay(main).setCurrent(this);
       imageCanvas = null;
   }

8. Create showMessage method to display the given message on the Screen.

   public void showMessage(AlertType alertType, String message) {
       Displayable currentDisplayable = Display.getDisplay(main).getCurrent();
   
       if (currentDisplayable != this || currentDisplayable != imageCanvas) {
           if (imageCanvas != null) {
               Display.getDisplay(main).setCurrent(imageCanvas);
           }
           else {
               Display.getDisplay(main).setCurrent(this);
           }
       }
   
       String title = null;
   
       if (alertType == AlertType.ERROR) {
           title = "Error";
       }
       else {
           title = null;
       }
   
       Alert errorAlert = new Alert(title, message, logoImage, alertType);
       errorAlert.setTimeout(ERROR_DIALOG_TIMEOUT);
       Display.getDisplay(main).setCurrent(errorAlert);
   }
   }