quotesmidlet.java

举例说明了J2ME 使用RMS 对数据的存储的编程.关于RMS相关方法都进行了使用。

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 * 
 * Copyright 1994-2004 Sun Microsystems, Inc. All Rights Reserved.
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 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *  
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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import javax.microedition.rms.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.microedition.io.*;
import java.io.*;
import java.util.Vector;

public class QuotesMIDlet extends MIDlet implements CommandListener {
    Display display = null;
    List menu = null; // main menu
    List choose = null;
    TextBox input = null;
    Ticker ticker = new Ticker("Database Application");
    String quoteServer = "http://quote.yahoo.com/d/quotes.csv?s=";
    String quoteFormat = "&f=slc1wop";

    static final Command backCommand = new Command("Back", Command.BACK, 0);
    static final Command mainMenuCommand = new Command("Main", Command.SCREEN, 1);
    static final Command saveCommand = new Command("Save", Command.OK, 2);
    static final Command exitCommand = new Command("Exit", Command.STOP, 3);
    String currentMenu = null;

    // Stock data
    String name, date, price;

    StockDB db = null;

    public QuotesMIDlet() {
    }

    public void startApp() throws MIDletStateChangeException {
      display = Display.getDisplay(this);
      // open a db stock file
      try {
        db = new StockDB("stocks");
      } catch(Exception e) {}
      menu = new List("Stocks Database", Choice.IMPLICIT);
      menu.append("List Stocks", null);
      menu.append("Add A New Stock", null);
      menu.addCommand(exitCommand);
      menu.setCommandListener(this);
      menu.setTicker(ticker);

      mainMenu();
    }

    public void pauseApp() {
      display = null;
      choose = null;
      menu = null;
      ticker = null;
       
      try {
        db.close();
        db = null;
      } catch(Exception e) {}
    }

    public void destroyApp(boolean unconditional) {
      try {
        db.close();
      } catch(Exception e) {}
      notifyDestroyed();
    }

    void mainMenu() {
      display.setCurrent(menu);
      currentMenu = "Main"; 
    }

    public String tickerString() {
       StringBuffer ticks = null;
       try {
          RecordEnumeration enum = db.enumerate();
          ticks = new StringBuffer();
          while(enum.hasNextElement()) {
            String stock1 = new String(enum.nextRecord());
            ticks.append(Stock.getName(stock1));
            ticks.append(" @ ");
            ticks.append(Stock.getPrice(stock1));
            ticks.append("    ");
          }
       } catch(Exception ex) {}
       return (ticks.toString());
    }

    public void addStock() {
      input = new TextBox("Enter a Stock Name:", "", 5, TextField.ANY);
      input.setTicker(ticker);
      input.addCommand(saveCommand);
      input.addCommand(backCommand);
      input.setCommandListener(this);
      input.setString("");
      display.setCurrent(input);
      currentMenu = "Add";
    }

    public String getQuote(String input) throws IOException, NumberFormatException {
      String url = quoteServer + input + quoteFormat;
      StreamConnection c = (StreamConnection)Connector.open(url, Connector.READ_WRITE);
      InputStream is = c.openInputStream();
      StringBuffer sb = new StringBuffer();
      int ch;
      while((ch = is.read()) != -1) {
        sb.append((char)ch);
      }
      return(sb.toString());
    }
   
    public void listStocks() {
        choose = new List("Choose Stocks", Choice.MULTIPLE);
        choose.setTicker(new Ticker(tickerString()));
        choose.addCommand(backCommand);
        choose.setCommandListener(this);
      try {
         RecordEnumeration re = db.enumerate();
         while(re.hasNextElement()) {
           String theStock = new String(re.nextRecord());
           choose.append(Stock.getName(theStock)+" @ " + Stock.getPrice(theStock), null);
         }
      } catch(Exception ex) {}
      display.setCurrent(choose);
      currentMenu = "List"; 
   }
 
  
   public void commandAction(Command c, Displayable d) {
      String label = c.getLabel();
      if (label.equals("Exit")) {
         destroyApp(true);
      } else if (label.equals("Save")) {
          if(currentMenu.equals("Add")) {
              // add it to database
            try {
              String userInput = input.getString();
              String pr = getQuote(userInput);
              db.addNewStock(pr);
              ticker.setString(tickerString()); 
              
            } catch(IOException e) {
            } catch(NumberFormatException se) {
            }
            mainMenu();
          } 

      } else if (label.equals("Back")) {
          if(currentMenu.equals("List")) {
            // go back to menu
            mainMenu();
          } else if(currentMenu.equals("Add")) {
            // go back to menu
            mainMenu();
          }

      } else {
         List down = (List)display.getCurrent();
         switch(down.getSelectedIndex()) {
           case 0: listStocks();break;
           case 1: addStock();break;
         }
            
      }
  }
}