Persistent Ranking MIDlet example Java code example - Click here to copy ->>>

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Code:



 

 package ora.ch6;



import java.io.IOException;

import java.util.Vector;

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.List;

import javax.microedition.lcdui.Screen;

import javax.microedition.lcdui.StringItem;

import javax.microedition.lcdui.TextField;

import javax.microedition.midlet.MIDlet;

import javax.microedition.midlet.MIDletStateChangeException;

import javax.microedition.rms.RecordEnumeration;

import javax.microedition.rms.RecordListener;

import javax.microedition.rms.RecordStore;

import javax.microedition.rms.RecordStoreException;





public class PersistentRankingMIDlet extends MIDlet

                implements CommandListener, RecordListener, Runnable {



    private Command exitCommand;

    private Command okCommand;

    private Command cancelCommand;

    private Command newCommand;

    private Command checkCommand;

    private Command detailsCommand;

    private Command backCommand;

    private Command deleteCommand;

    private Display display;

    private TextField isbnField;

    private StringItem isbnDisplay;

    private StringItem titleDisplay;

    private StringItem rankingDisplay;

    private StringItem reviewDisplay;

    private StringItem checkTitle;

    private Form isbnForm;

    private Form searchForm;

    private Form resultForm;

    private Form checkForm;

    private List bookList;

    private Vector bookInfoList;

    private Thread searchThread;

    private BookStore bookStore;

    private BookInfo searchBookInfo;



    protected void startApp() throws MIDletStateChangeException {

        if (display == null) {

            initialize();



            // If there are any books in the

            // book store, display the list.

            // Otherwise, start with the ISBN form.

            display.setCurrent(getSelectionScreen());

        }

    }



    protected void pauseApp() {

    }



    protected void destroyApp(boolean unconditional)

                        throws MIDletStateChangeException {

        // Close the book store

        if (bookStore != null) {

            try {

                bookStore.removeRecordListener(this);

                bookStore.close();

            } catch (RecordStoreException ex) {

            }

        }

    }



    public void commandAction(Command cmd, Displayable d) {

        if (cmd == exitCommand) {

            try {

                destroyApp(true);

            } catch (MIDletStateChangeException ex) {

            }

            notifyDestroyed();

        } else if (cmd == okCommand) {

            String isbn = isbnField.getString().trim();

            if (!isbn.equals("")) {

                isbnDisplay.setText(isbn);

                display.setCurrent(searchForm);

                searchForBook(new BookInfo(isbn));

            }

        } else if (cmd == cancelCommand) {

            searchThread = null;

            isbnField.setString(null);

            display.setCurrent(getSelectionScreen());

        } else if (cmd == newCommand) {

            isbnField.setString(null);

            display.setCurrent(isbnForm);

        } else if (cmd == detailsCommand || cmd == List.SELECT_COMMAND) {

            int index = bookList.getSelectedIndex();

            searchBookInfo = (BookInfo)bookInfoList.elementAt(index);

            isbnDisplay.setText(searchBookInfo.getIsbn());

            showBookInfo(searchBookInfo);

        } else if (cmd == deleteCommand) {

            int index = bookList.getSelectedIndex();

            BookInfo bookInfo = (BookInfo)bookInfoList.elementAt(index);

            try {

                bookStore.deleteBook(bookInfo);

            } catch (RecordStoreException ex) {

                System.out.println("Delete failed: " + ex);

            }

        } else if (cmd == checkCommand) {

            String isbn = searchBookInfo.getIsbn();

            checkTitle.setText(searchBookInfo.getTitle());

            display.setCurrent(checkForm);

            searchForBook(searchBookInfo);

        } else if (cmd == backCommand) {

            display.setCurrent(getSelectionScreen());

        }

    }



    public void searchForBook(BookInfo info) {

        searchBookInfo = info;

        searchThread = new Thread(this);

        searchThread.start();

    }



    public void recordAdded(RecordStore recordStore, int recordId) {

        // Update the book list

        populateBookList();

    }



    public void recordChanged(RecordStore recordStore, int recordId) {

        // Update the book list

        populateBookList();

    }



    public void recordDeleted(RecordStore recordStore, int recordId) {

        // Update the book list

        populateBookList();

    }



    public void run() {

        try {

            boolean found = Fetcher.fetch(searchBookInfo);

            if (searchThread == Thread.currentThread()) {

                if (found && searchBookInfo.getTitle() != null) {

                    // Display the book details

                    showBookInfo(searchBookInfo);



                    // Add the new book to the book store

                    bookStore.saveBookInfo(searchBookInfo);

                } else {

                    Alert alert = new Alert("Book not found", null,

                                        null, AlertType.ERROR);

                    alert.setTimeout(Alert.FOREVER);

                    alert.setString("No book with ISBN " +

                                        searchBookInfo.getIsbn() +

                                        " was found.");

                    isbnField.setString(null);

                    display.setCurrent(alert, getSelectionScreen());

                }

            }

        } catch (Throwable ex) {

            if (searchThread == Thread.currentThread()) {

                Alert alert = new Alert("Search Failed", null,

                                        null, AlertType.ERROR);

                alert.setTimeout(Alert.FOREVER);

                alert.setString("Search failed:\n" + ex.getMessage());

                isbnField.setString(null);

                display.setCurrent(alert, getSelectionScreen());

            }

        }

    }



    // Shows book details on the result screen

    private void showBookInfo(BookInfo info) {

        titleDisplay.setText(info.getTitle());



        int ranking = info.getRanking();

        int lastRanking = info.getLastRanking();

        int change = ranking - lastRanking;

        String rankingText =

                ranking == 0 ? "" :

                    String.valueOf(ranking);

        if (change > 0) {

            rankingText += ", down by " + change;

        } else if (change < 0) {

            rankingText += ", UP by " + (-change);

        }

        rankingDisplay.setText(rankingText);



        int reviews = info.getReviews();

        int lastReviews = info.getLastReviews();

        change = reviews - lastReviews;

        String reviewText =

            reviews == 0 ? "" :

                    String.valueOf(reviews);

        if (change > 0) {

            reviewText += ", up by " + change;

        }

        reviewDisplay.setText(reviewText);



        display.setCurrent(resultForm);

    }



    // If there are any books in the

    // book store, display the list.

    // Otherwise, start with the ISBN form.

    private Screen getSelectionScreen() {

        return

            bookInfoList.isEmpty() ? (Screen)isbnForm : (Screen)bookList;

    }



    // Populates the list of books

    private void populateBookList() {

        // Clear out any existing content

        int count = bookList.size();

        for (int i = 0; i < count; i++) {

            bookList.delete(0);

        }

        bookInfoList.removeAllElements();



        // Add an entry for each book in the store

        try {

            RecordEnumeration enum = bookStore.getBooks();

            while (enum.hasNextElement()) {

                int id = enum.nextRecordId();

                BookInfo info = bookStore.getBookInfo(id);

                bookInfoList.addElement(info);

                String title = info.getTitle();

                if (title == null || title.equals("")) {

                    title = info.getIsbn();

                }

                bookList.append(title, null);

            }

            enum.destroy();

        } catch (Exception ex) {

            // Just leave an empty list.

        }



        // The ISBN list should have an exit command

        // only if the List screen is empty.

        isbnForm.removeCommand(exitCommand);

        if (bookInfoList.isEmpty()) {

            isbnForm.addCommand(exitCommand);

        }

    }



    private void initialize() {

        display = Display.getDisplay(this);



        // Open the book store

        bookStore = new BookStore();



        exitCommand = new Command("Exit", Command.EXIT, 0);

        okCommand = new Command("OK", Command.OK, 0);

        cancelCommand = new Command("Cancel", Command.CANCEL, 0);

        newCommand = new Command("New", Command.SCREEN, 1);

        detailsCommand = new Command("Details", Command.OK, 0);

        checkCommand = new Command("Check", Command.OK, 0);

        backCommand = new Command("Back", Command.CANCEL, 1);

        deleteCommand = new Command("Delete", Command.SCREEN, 1);



        bookList = new List("Books", List.IMPLICIT);

        bookList.addCommand(detailsCommand);

        bookList.addCommand(newCommand);

        bookList.addCommand(deleteCommand);

        bookList.addCommand(exitCommand);

        bookInfoList = new Vector();



        isbnForm = new Form("Book Query");

        isbnForm.append("Enter an ISBN and press OK:");

        isbnField = new TextField("", null, 10, TextField.ANY);

        isbnForm.append(isbnField);

        isbnForm.addCommand(okCommand);

        isbnForm.addCommand(exitCommand);

        isbnForm.addCommand(backCommand);



        searchForm = new Form("Book Search");

        searchForm.append("Searching for ISBN\n");

        isbnDisplay = new StringItem(null, null);

        searchForm.append(isbnDisplay);

        searchForm.append("\nPlease wait....");

        searchForm.addCommand(cancelCommand);



        checkForm = new Form("Details Update");

        checkForm.append("Getting details for\n");

        checkTitle = new StringItem(null, null);

        checkForm.append(checkTitle);

        checkForm.append(" from amazon.com\nPlease wait....");

        checkForm.addCommand(cancelCommand);



        resultForm = new Form("Search Results");

        titleDisplay = new StringItem("Book title: ", null);

        rankingDisplay = new StringItem("Ranking:    ", null);

        reviewDisplay = new StringItem("Reviews:    ", null);

        resultForm.append(titleDisplay);

        resultForm.append(rankingDisplay);

        resultForm.append(reviewDisplay);

        resultForm.addCommand(backCommand);

        resultForm.addCommand(checkCommand);



        // Register for events from all of the forms

        isbnForm.setCommandListener(this);

        searchForm.setCommandListener(this);

        resultForm.setCommandListener(this);

        bookList.setCommandListener(this);



        // Listen for changes in the content of the book store

        bookStore.addRecordListener(this);



        // Install the books held in the record store

        populateBookList();

    }

}

J2ME in a Nutshell

By Kim Topley

First Edition March 2002

Series: In a Nutshell

ISBN: 0-596-00253-X