buycreditscreen.java

利用javame开发的

// Copyright 2002 Nokia Corporation. 
// 
// THIS SOURCE CODE IS PROVIDED 'AS IS', WITH NO WARRANTIES WHATSOEVER, 
// EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF MERCHANTABILITY, FITNESS 
// FOR ANY PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE 
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// OF ANY PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OWNED OR CONTROLLED 
// BY THIRD PARTIES 
// 
// Furthermore, information provided in this source code is preliminary, 
// and may be changed substantially prior to final release. Nokia Corporation 
// retains the right to make changes to this source code at 
// any time, without notice. This source code is provided for informational 
// purposes only. 
// 
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// Corporation.
// Java and all Java-based marks are trademarks or registered trademarks of
// Sun Microsystems, Inc.
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// trade names of their respective owners.
// 
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package example.fruitmachine;

import javax.microedition.lcdui.*;
import java.io.IOException;


class BuyCreditScreen
    extends Form
    implements CommandListener, HttpPosterListener
{
    private final FruitMachineMIDlet midlet;
    private final HttpPoster httpPoster;
    private final Account account;
    private final StringItem creditItem;
    private final TextField purchaseField;
    private final Command buyCommand;
    private final Command cancelCommand;
    private volatile boolean readyForInput = true;

    private static final int DEFAULT_PURCHASE = 10;


    BuyCreditScreen(FruitMachineMIDlet midlet,
                    HttpPoster httpPoster,
                    Image logoImage,
                    Account account)
    {
        super("Buy Credit");
        this.midlet = midlet;
        this.httpPoster = httpPoster;
        this.account = account;

        append(logoImage);
        creditItem = new StringItem("Credit:", "");
        append(creditItem);
        purchaseField = new TextField("Buy:", "", 3, TextField.NUMERIC);
        append(purchaseField);
        buyCommand = new Command("Buy", Command.SCREEN, 2);
        addCommand(buyCommand);
        cancelCommand = new Command("Cancel", Command.EXIT, 2);
        addCommand(cancelCommand);

        setCommandListener(this);
    }

    
    public void commandAction(Command c, Displayable d)
    {
        if (!readyForInput)
        {
            return;
        }

        if (c == buyCommand)
        {
            // start the buy
            try
            {
                int purchase = Integer.parseInt(purchaseField.getString());
                sendBuyRequest(purchase);
                readyForInput = false;
            }
            catch (NumberFormatException e)
            {
                ErrorScreen.showError("Purchase must be a whole number");
                purchaseField.setString(Integer.toString(DEFAULT_PURCHASE));
            }
            catch (IOException e)
            {
                ErrorScreen.showError("Communications error");
            }
        }
        else if (c == cancelCommand)
        {
            midlet.buyCreditScreenDone();
        }
    }


    void updateValues()
    {
        creditItem.setText(Integer.toString(account.getCredit()));
        purchaseField.setString(Integer.toString(DEFAULT_PURCHASE));
    }


    private void sendBuyRequest(int purchase)
        throws IOException
    {
        ValueGenerator generator = new ValueGenerator();
        generator.addValue("buy");
        generator.addValue(Integer.toString(purchase));
        String dataStr = generator.getString();
        httpPoster.sendRequest(dataStr, this);
    }


    public void receiveHttpResponse(String responseStr)
    {
        ValueParser parser = new ValueParser(responseStr);
        String response = parser.getNextValue();
        if ("buy-OK".equals(response))    // no harm if response is null
        {
            try
            {
                int credit = parser.getNextIntValue();
                account.setCredit(credit);
                midlet.buyCreditScreenDone();
            }
            catch (NumberFormatException e)
            {
                ErrorScreen.showError("Server error");
            }
        }
        else if ("buy-error".equals(response))
        {
            String errorMessage = parser.getNextValue();
            if (errorMessage != null)
            {
                ErrorScreen.showError(errorMessage);
            }
            else
            {
                ErrorScreen.showError("Server error");
            }
        }
        else
        {
            ErrorScreen.showError("Server error");
        }
        readyForInput = true;
    }


    public void handleHttpError(String errorStr)
    {
        ErrorScreen.showError("Error communicating with server");
        readyForInput = true;
    }
}