Unhandled Exception

[adityasoni03]

Hi,
I have been trying to build a location based application. For tht i hav used network parameters and gt the location frm a stored database of n/w parameters and their corresponding positions. Sometimes the application runs correctly bt sometimes i get an unhandled exception.
I am attaching the code.

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.microedition.io.Connector;
import javax.microedition.io.ContentConnection;
import javax.microedition.io.StreamConnection;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

public class HelloWorld extends MIDlet implements CommandListener{
private Form form;
private Display display;
private Command exit = new Command("Exit", Command.EXIT, 1);

String url = "";
private String S60_cell_id;
private String Signal;
private Form form1;
private Command cmExit;
private Command cmView;
private Form fmViewPng;
String loc = null;
public HelloWorld(){
super();
}



public void startApp(){
form = new Form("Hello World");
String msg = "Hello World!!!!!!!";
form.append(msg);
form.addCommand(exit);
cmView = new Command("View", Command.SCREEN, 2);
form.addCommand(cmView);
display = Display.getDisplay(this);
display.setCurrent(form);
S60_cell_id = System.getProperty("com.nokia.mid.cellid");
Signal = System.getProperty("com.nokia.mid.networksignal");
// S60_cell_id="1351";
// Signal="78";
url = "http://locateme.co.in/welcome.php?cellid="+S60_cell_id+"&signal="+Signal;
form.setCommandListener(this);
connection(url);


}

public void pauseApp(){}

public void exit(){
destroyApp(false);
notifyDestroyed();
}

public void destroyApp(boolean unconditional){
notifyDestroyed();
}



private void connection(String url) {
StreamConnection sc = null;
InputStream is = null;
StringBuffer buffer = new StringBuffer();

try {

sc = (StreamConnection) Connector.open(url);
is = sc.openInputStream();
int chars;
while ((chars = is.read()) != -1) {
if ((chars != ' ')&&(chars!='\n')) {
buffer.append((char) chars);
}
}
System.out.println(buffer.toString());
loc = buffer.toString();
form.append(loc);



} catch (IOException ex1) {
ex1.printStackTrace();
}

finally{
if(is != null){
try {
is.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
if(sc != null){
try {
sc.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}


}

public void commandAction(Command c, Displayable d) {
if (c == exit) {
exit();
}
if (c == cmExit)
{
destroyApp(false);
notifyDestroyed();
}
else if (c == cmView)
{
int width = form.getWidth();
int height = form.getHeight();
url ="http://maps.google.com/maps/api/staticmap?center="+loc+"&format=png32&zoom=14&size="+width+"x"+height+"&markers=color:blue|label:S|"+loc+"&sensor=true&key=ABQIAAAAe-XrGezTSfvomiYHOAdjexSrqYa9FVv0ZzmTKrWlYncjiNW5DhSw7OuYiFstDeXcRsMloWpJpsiXrQ";
// url = "http://maps.google.com/staticmap?center=" + loc + "&format=png32&zoom=15&size="+width+"x"+height + "&key=ABQIAAAAiyHApDe39izCxX3VkLY8jhSrqYa9FVv0ZzmTKrWlYncjiNW5DhSt_6ACgssm3qmm3HiM6dN0jctQhQ";

cmExit = new Command("Exit", Command.EXIT, 1);


// Create the form that will hold the png image
fmViewPng = new Form("");
display.setCurrent(fmViewPng);

fmViewPng.addCommand(cmExit);

// Set up a listener for form
fmViewPng.setCommandListener(this);
// Download image and place on the form
try
{
Image im;

if ((im = getImage(url)) != null)
{
ImageItem ii = new ImageItem(null, im, ImageItem.LAYOUT_DEFAULT, null);

// If there is already an image, set (replace) it
if (fmViewPng.size() != 0)
fmViewPng.set(0, ii);
else // Append the image to the empty form
fmViewPng.append(ii);
}
else
fmViewPng.append("Unsuccessful download.");

// Display the form with the image
display.setCurrent(fmViewPng);
}
catch (Exception e)
{
System.err.println("Msg: " + e.toString());
}


}

}

private Image getImage(String url) throws IOException
{
ContentConnection connection = (ContentConnection) Connector.open(url);

// * There is a bug in MIDP 1.0.3 in which read() sometimes returns
// an invalid length. To work around this, I have changed the
// stream to DataInputStream and called readFully() instead of read()
// InputStream iStrm = connection.openInputStream();
DataInputStream iStrm = connection.openDataInputStream();

ByteArrayOutputStream bStrm = null;
Image im = null;

try
{
// ContentConnection includes a length method
byte imageData[];
int length = (int) connection.getLength();
if (length != -1)
{
imageData = new byte[length];

// Read the png into an array
// iStrm.read(imageData);
iStrm.readFully(imageData);
}
else // Length not available...
{
bStrm = new ByteArrayOutputStream();

int ch;
while ((ch = iStrm.read()) != -1)
bStrm.write(ch);

imageData = bStrm.toByteArray();
bStrm.close();
}

// Create the image from the byte array
im = Image.createImage(imageData, 0, imageData.length);
}
finally
{
// Clean up
if (iStrm != null)
iStrm.close();
if (connection != null)
connection.close();
if (bStrm != null)
bStrm.close();
}
return (im == null ? null : im);
}
}

[grahamhughes]

I'm afraid I can't spot code that throws an exception without some clues. Do you not have any details of the exception? Such as, which exception?

I can tell you that you will have problems with this code, as you perform connections inside events. Event methods (like startApp() and commandAction()) need to return as quickly as possible, since the entire event mechanism is blocked while an event is being handled. Use a Thread to perform any time consuming action.

Try to find out more about the exception. Can you reproduce the problem in an emulator? If not, add some try..catch blocks to see what you can catch.

Graham.

[vinuk4u]

Can u pls specify that at what stage this exception is caught? ie, when clicking any commands or anything....

[adityasoni03]

Graham, thanks a lot...
we will try it with threads.

[adityasoni03]

vinuk,
the exception comes as soon as i start the application and sometimes the application runs correctly.