whiteboardmidlet.java

J2ME MIDP_Example_Applications

// Copyright 2003 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
// OR TRADE PRACTICE, RELATING TO THE SOURCE CODE OR ANY WARRANTY OTHERWISE
// ARISING OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE AND WITH NO
// OBLIGATION OF NOKIA TO PROVIDE THE LICENSEE WITH ANY MAINTENANCE OR
// SUPPORT. FURTHERMORE, NOKIA MAKES NO WARRANTY THAT EXERCISE OF THE
// RIGHTS GRANTED HEREUNDER DOES NOT INFRINGE OR MAY NOT CAUSE INFRINGEMENT
// 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.
//
// Nokia and Nokia Connecting People are registered trademarks of Nokia
// Corporation.
// Java and all Java-based marks are trademarks or registered trademarks of
// Sun Microsystems, Inc.
// Other product and company names mentioned herein may be trademarks or
// trade names of their respective owners.
//
// A non-exclusive, non-transferable, worldwide, limited license is hereby
// granted to the Licensee to download, print, reproduce and modify the
// source code. The licensee has the right to market, sell, distribute and
// make available the source code in original or modified form only when
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// intellectual property rights is granted herein.
package whiteboard;

import java.io.*;

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

public class WhiteboardMIDlet
    extends MIDlet
    implements HttpPosterListener
{
    private final Image logo;
    private final WhiteboardScreen displayable;
    private final HttpPoster poster;
    private final ActivityIndicator activityIndicator;


    public WhiteboardMIDlet()
    {
        // initialize final variables
        logo = makeImage("/logo.png");
        ErrorScreen.init(logo, Display.getDisplay(this));
        displayable = new WhiteboardScreen(this);
        poster = new HttpPoster(getAppProperty("Servlet-URL"));
        activityIndicator = new ActivityIndicator(this);
    }


    public void startApp()
    {
        Displayable current = Display.getDisplay(this).getCurrent();

        if (current == null)
        {
            // the first time we are called display a splash screen
            String text = getAppProperty("MIDlet-Name") + "\n" +
                getAppProperty("MIDlet-Vendor");
            Alert splashScreen = new Alert(null,
                                           text,
                                           logo,
                                           AlertType.INFO);
            splashScreen.setTimeout(3000);
            Display.getDisplay(this).setCurrent(splashScreen, displayable);
        }
        else
        {
            Display.getDisplay(this).setCurrent(current);
        }

    }


    // loads a given image by name
    static Image makeImage(String filename)
    {
        Image image = null;

        try
        {
            image = Image.createImage(filename);
        }
        catch (Exception e)
        {
            // use a null image instead
        }

        return image;
    }


    public void pauseApp()
    {
    }


    public void destroyApp(boolean unconditional)
    {
        poster.abort();
    }


    // Loads the whiteboard sending an empty request
    void loadWhiteboard()
    {
        try
        {
            activityIndicator.startProgressMeter();
            activityIndicator.setText("Loading Whiteboard");
            Display.getDisplay(this).setCurrent(activityIndicator);
            poster.sendRequest(HttpConnection.GET, "", this);
        }
        catch (IOException e)
        {
            ErrorScreen.showError(e.getMessage(), displayable);
        }
    }


    // Shows the send message screen
    void showSendMessage()
    {
        Display.getDisplay(this).setCurrent(new SendMessageForm(this));
    }


    void abortRequest()
    {
        poster.abort();
        showWhiteboard();
    }


    // Send a message with a post request
    void sendMessage(String string)
    {
        try
        {
            activityIndicator.startProgressMeter();
            activityIndicator.setText("Updating Whiteboard");
            Display.getDisplay(this).setCurrent(activityIndicator);
            // use form enconding to simplify the server side handling
            // but it needs to be encoded
            poster.sendRequest(
                HttpConnection.POST,
                "application/x-www-form-urlencoded;charset=UTF-8",
                "msg=" + HttpUtils.encodeURL(string),
                this);
        }
        catch (IOException e)
        {
            ErrorScreen.showError(e.getMessage(), displayable);
        }
    }


    // Shows the whiteboard screen
    void showWhiteboard()
    {
        Display.getDisplay(this).setCurrent(displayable);
    }


    // HttpPoster listener callback
    public void receiveHttpResponse(String response)
    {
        // parse the answer
        Vector result = doParsing(response);
        displayable.whiteboardUpdated(result);
        activityIndicator.stopProgressMeter();
        showWhiteboard();
    }


    public void handleHttpError(String errorStr)
    {
        activityIndicator.stopProgressMeter();
        ErrorScreen.showError(errorStr, displayable);
    }


    // Parses the whiteboard response
    private Vector doParsing(String response)
    {
        ValueParser parser = new ValueParser(response);
        int count = parser.getNextIntValue();
        Vector messages = new Vector();
        for (int i = 0; i < count; i++)
        {
            String user = parser.getNextValue();
            String timestamp = parser.getNextValue();
            String msg = parser.getNextValue();
            messages.addElement(new Message(user, timestamp, msg));
        }
        return messages;
    }

}