photoalbum.java

Sun公司的J2ME官方例程若干

/*
 * @(#)PhotoAlbum.java	1.6 01/04/04
 *
 * Copyright (c) 2000-2001 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 */

package examples.photoalbum;

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.util.Vector;

/**
 * The PhotoAlbum MIDlet class provides the commands and screens
 * that implement a simple Photo and Animation Album.
 * The images and animations to be displayed are configured
 * in the descriptor file with attributes.
 * <p>
 * It provides simple options to vary the speed of display
 * and the picture frames used.
 *
 */
public class PhotoAlbum extends MIDlet 
	implements CommandListener, ItemStateListener
{

	private Display display;		// The display for this MIDlet
	private PhotoFrame frame;	// The Frame and Canvas for images

	private ChoiceGroup borderChoice; // List of border choices
	private ChoiceGroup speedChoice;	// List of speed choices

	private Form optionsForm;	// The form holding the options
	private Alert alert;		// The Alert used for errors

	private Vector imageNames;	// Strings with the image names
	private List imageList;		// List of Image titles

	private Command exitCommand;	// The exit command
	private Command okCommand;	// The ok command
	private Command optionsCommand;	// The command to edit options
	private Command backCommand;	// The command to go back

	/**
	 * Construct a new PhotoAlbum MIDlet and initialize the base
	 * options and main PhotoFrame to be used when the MIDlet is
	 * started.
	 */
	public PhotoAlbum() {  
		display = Display.getDisplay(this);
		exitCommand = new Command("Exit", Command.EXIT, 1);
		optionsCommand = new Command("Options", Command.SCREEN, 1);
		okCommand = new Command("Ok", Command.OK, 3);
		backCommand = new Command("Back", Command.SCREEN, 3);

		frame = new PhotoFrame();
		frame.setStyle(2);
		frame.setSpeed(2);
		frame.addCommand(optionsCommand);
		frame.addCommand(backCommand);
		frame.setCommandListener(this);
		alert = new Alert("Warning");
		setupImages();
	}

	/**
	 * Start up the MIDlet by setting the display
	 * to show the image name list.
	 */
	protected void startApp() {
		display.setCurrent(imageList);
	}

	/**
	 * Pausing is easy since there are no background activities
	 * or record stores that need to be closed.
	 */
	protected void pauseApp() {
		frame.reset();		// Discard images cached in the frame
	}

	/**
	 * Destroy must cleanup everything not handled by the garbage
	 * collector.
	 */
	protected void destroyApp(boolean unconditional) {
		frame.reset();		// Discard images cached in the frame
	}

	/**
	 * Respond to commands, including exit.
	 * On the exit command, cleanup and notify that
	 * the MIDlet has been destroyed.
	 */
	public void commandAction(Command c, Displayable s) {
		if (c == exitCommand) {
			destroyApp(false);
			notifyDestroyed();
		} else if (c == optionsCommand) {
			display.setCurrent(genOptions());
		} else if (c == okCommand && s == optionsForm) {
			display.setCurrent(frame);
		} else if (c == List.SELECT_COMMAND) {
			int i = imageList.getSelectedIndex();
			String image = (String)imageNames.elementAt(i);

			try {
				frame.setImage(image);
				display.setCurrent(frame);
			} catch (java.io.IOException e) {
				alert.setString("Unable to locate " + image);
				display.setCurrent(alert, imageList);
			}

		} else if (c == backCommand) {
			display.setCurrent(imageList);
		}
	}

	/**
	 * Listener for changes to options.
	 */
	public void itemStateChanged(Item item) {
		if (item == borderChoice) {
			frame.setStyle(borderChoice.getSelectedIndex());
		} else if (item == speedChoice) {
			frame.setSpeed(speedChoice.getSelectedIndex());
		}
	}

	/**
	 * Generate the options form with speed and style choices.
	 * Speed choices are stop, slow, medium, and fast.
	 * Style choices for borders are none, plain, fancy.
	 */
	private Screen genOptions() {
		if (optionsForm == null) {
			optionsForm = new Form("Options");
			optionsForm.addCommand(okCommand);
			optionsForm.setCommandListener(this);
			optionsForm.setItemStateListener(this);

			speedChoice = new ChoiceGroup("Speed", 
						      Choice.EXCLUSIVE);
			speedChoice.append("Stop", null);
			speedChoice.append("Slow", null);
			speedChoice.append("Medium", null);
			speedChoice.append("Fast", null);
			speedChoice.setSelectedIndex(2, true);
			optionsForm.append(speedChoice);

			borderChoice = new ChoiceGroup("Borders",
						       Choice.EXCLUSIVE);
			borderChoice.append("None", null);
			borderChoice.append("Plain",  null);
			borderChoice.append("Fancy", null);
			borderChoice.setSelectedIndex(2, true);
			optionsForm.append(borderChoice);
		}

		return optionsForm;
	}
    
	/**
	 * Check the attributes in the Descriptor that identify
	 * images and titles and initialize the lists imageNames
	 * and imageList.
	 */
	private void setupImages() {
		imageNames = new Vector();
		imageList = new List("Images", List.IMPLICIT);
		imageList.addCommand(exitCommand);
		imageList.setCommandListener(this);

		for (int n = 1; n < 100; n++) {
			String nthImage = "PhotoImage-"+ n;
			String image = getAppProperty(nthImage);
			if (image == null || image.length() == 0)
				break;

			String nthTitle = "PhotoTitle-" + n;
			String title = getAppProperty(nthTitle);
			if (title == null || title.length() == 0)
				title = image;

			imageNames.addElement(image);
			imageList.append(title, null);
		}
	}
}