Strange bug with getSupportedContentTypes()

[anderssl]

Hey,
I am trying to do audio streaming with jme on a Nokia Navigator 6110. I have read the docs and some threads on this, and it doesn't seem clear whether it's possible to do real streaming at all in jme, so as a start I decided to test the output from getSupportedContentTypes and getSupportedProtocols, like so many recommend... But even this doesn't seem to work properly.

Here's where it crashes:

try {
  protocols = Manager.getSupportedProtocols(contenttype);
  test = "Number of protocols: " + protocols.length + "\n";
				
  if (protocols != null && protocols[0] != null)
    test +=  protocols[0] + "\n";
				
  for(int i=0; i<protocols.length; i++){
    test += protocols[i] + "\n";
  }
				
}
catch (Exception e){
  test = "Something went wrong when finding protocols: " + e.getMessage();
}

If I comment out the for-loop, everything is fine: It prints out the length of the array, and the first entry in the array. But somehow the for-loop makes it crash (in S60 emulator it gives an unhandled exception - even though I am catching all exceptions! In the phone the script just freezes). The behaviour seems to be the same with getSupportedContentTypes(). But very erratic.

I suspect I must be doing some really stupid mistake, but I can't see it myself. Can anyone help me please?

I'm posting the entire code below.

[anderssl]

Here's the entire code. Basically it sets up a form with two fields, where you can test either a given protocol or a content type - and get a list of supported types/protocols in a separate textbox.

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.media.*;

public class Streamtest extends MIDlet implements CommandListener {

	private TextBox textbox;
	private Form form;
	private TextField pField, cField;
	private Display display;
	private Command protocolCommand, contentCommand, exitCommand, backCommand;
	
	private String test = "";
	private String[] supported = new String[30];
	private String[] protocols = new String[10];
	
	public Streamtest() {
		form = new Form("Media protocols test");
		
		pField = new TextField("Protocol:", "http", 100, TextField.ANY);
		cField = new TextField("Content type:", "audio/mpeg", 100, TextField.ANY);
		
		protocolCommand = new Command("Test protocol", Command.SCREEN, 0);
		contentCommand = new Command("Test content", Command.SCREEN, 0);
		exitCommand = new Command("Exit", Command.EXIT, 1);
		
		backCommand = new Command("Back", Command.SCREEN, 1);
	    
		form.append(pField);
		form.append(cField);
		form.addCommand(protocolCommand);
		form.addCommand(contentCommand);
		form.addCommand(exitCommand);
		form.setCommandListener(this);
		
		display = Display.getDisplay(this);
		
		
		
		
	}
	
	public void findContentTypes(String protocol){
		if (protocol != null && protocol != ""){
			// showAlert("Starting test","Protocol: " + protocol);
			try {

				supported = Manager.getSupportedContentTypes(protocol);
				test = "Number of content types: " + supported.length + "\n";
				
				if (supported != null && supported[0] != null) test += supported[0];
				
				for(int i=0; i<supported.length; i++){
					test += supported[i] + "\n";
				}
				
				
			}
			catch (Exception e){
				test = "Something went wrong:" + e.getMessage();
			}
		}
		else {
			test = "The protocol variable is empty; did you forget to write something in the protocol field?";
		}

		textbox = new TextBox("Streaming test", test, 32, 0);
		textbox.addCommand(exitCommand);
		textbox.addCommand(backCommand);
		textbox.setCommandListener(this);
		display.setCurrent(textbox);
	}
	
	public void findProtocols(String contenttype){
		if (contenttype != null && contenttype != ""){
			try {
				protocols = Manager.getSupportedProtocols(contenttype);
				test = "Number of protocols: " + protocols.length + "\n";
				
				if (protocols != null && protocols[0] != null) test += protocols[0] + "\n";
				
				for(int i=0; i<protocols.length; i++){
					test += protocols[i] + "\n";
				}
				
			}
			catch (Exception e){
				test = "Something went wrong when finding protocols: " + e.getMessage();
			}
		}
		else {
			test = "The content variable is empty; did you forget to write something in the content field?";
		}

		textbox = new TextBox("Streaming test", test, 32, 0);
		textbox.addCommand(exitCommand);
		textbox.addCommand(backCommand);
		textbox.setCommandListener(this);
		display.setCurrent(textbox);
	}
	
	public void commandAction(Command c, Displayable s) {
		if (c == exitCommand){
			destroyApp(false);
			notifyDestroyed();
		}	
		else if	(c == protocolCommand){
			String teststring = pField.getString();
			findContentTypes(teststring);
		}
		else if (c == contentCommand){
			String teststring = cField.getString();
			findProtocols(teststring);
		}
		else if (c == backCommand){
			display.setCurrent(form);
			textbox = null;
		}
	}
	
	public void showAlert(String title, String message){
		Alert alert = new Alert(title, message, null, AlertType.ERROR);
		display.setCurrent(alert);
	}
	
	public void startApp(){
		display.setCurrent(form);
		
	}
	
	public void pauseApp(){
		
	}
	
	public void destroyApp(boolean condition){
		
	}
}

[jappit]

Hi anderssl,

try changing this line:

textbox = new TextBox("Streaming test", test, 32, 0);

to this:

textbox = new TextBox("Streaming test", test, 4000, TextField.ANY);

(the Exception you're getting could be due to the TextBox max allowed size you set, that is not enough to hold all the content-type/protocol names)

Pit

[anderssl]

I feel stupid. But thank you.

Actually there were some more bugs, but with your help I got sensible output so I could find the others.

I suspect this is trivial to most of you, but in case anyone else are having similar problems, I post my finished code here. It's a simple program in which you can enter the name of a protocol and get out which contenttypes can be used with it, or vice versa. Distribute freely.

/*
 * A simple test program for testing which media protocols are supported by a j2me phone,
 * and which content types can be used with certain protocols.
 * 
 * @author Anders Sundnes Løvlie
 * folk.uio.no/anderssl
 * a.s.lovlie at media.uio.no
 * 
 */


import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.media.*;

public class Streamtest extends MIDlet implements CommandListener {

	private TextBox textbox;
	private Form form;
	private TextField pField, cField;
	private Display display;
	private Command protocolCommand, contentCommand, exitCommand, backCommand;
	
	private String[] supported = new String[30];
	private String[] protocols = new String[10];
	
	public Streamtest() {
		// User interface
		
		form = new Form("Media protocols test");
		
		pField = new TextField("Protocol:", "http", 100, TextField.ANY);
		cField = new TextField("Content type:", "audio/mpeg", 100, TextField.ANY);
		
		protocolCommand = new Command("Test protocol", Command.SCREEN, 0);
		contentCommand = new Command("Test content", Command.SCREEN, 0);
		exitCommand = new Command("Exit", Command.EXIT, 1);
		
		backCommand = new Command("Back", Command.SCREEN, 1);
	    
		form.append(pField);
		form.append(cField);
		form.addCommand(protocolCommand);
		form.addCommand(contentCommand);
		form.addCommand(exitCommand);
		form.setCommandListener(this);
		
		display = Display.getDisplay(this);	
		
	}
	
	public void findContentTypes(String protocol){
		if (protocol != null && protocol != ""){
			try {
				supported = Manager.getSupportedContentTypes(protocol);
			}
			catch (Exception e){
				showAlert("Error", "Something went wrong when finding contenttypes:" + e);
				return;
			}
		}
		else {
			showAlert("Error", "The protocol variable is empty; did you forget to write something in the protocol field?");
			return;
		}
		displayResults(supported,protocol);
	}
	
	public void findProtocols(String contenttype){
		if (contenttype != null && contenttype != ""){
			try {
				protocols = Manager.getSupportedProtocols(contenttype);
			}
			catch (Exception e){
				showAlert("Error", "Something went wrong when finding protocols: " + e);
				return;
			}
		}
		else {
			showAlert("Error", "The content variable is empty; did you forget to write something in the content field?");
			return;
		}
	
		displayResults(protocols, contenttype);
	}
	
	public void displayResults(String[] results, String teststring){
		String output = "";
		try {
			if (results == null){
				output += "Error: '" + teststring + "' not supported on this phone. (Results was 'null'.)";
			}
			else if (results.length<1){
				output += "Error: '" + teststring + "' not supported on this phone. (Length of results was 0.)";
			}
			else if (results[0] == null){
				output += "Error: '" + teststring + "' not supported on this phone. (Result array is empty.)";
			}
			else {
				output = "Number of entries: " + results.length + "\n";
									
				for(int i=0; i<results.length; i++){
					output += results[i] + "\n";
				}
			}				
		}
		catch (Exception e){
			output = "Something went wrong when finding results: " + e;
		}
	
		textbox = new TextBox("Streaming test", output, 4000, TextField.ANY);
		textbox.addCommand(exitCommand);
		textbox.addCommand(backCommand);
		textbox.setCommandListener(this);
		display.setCurrent(textbox);
	}
	
	public void commandAction(Command c, Displayable s) {
		if (c == exitCommand){
			destroyApp(false);
			notifyDestroyed();
		}	
		else if	(c == protocolCommand){
			String teststring = pField.getString();
			findContentTypes(teststring);
		}
		else if (c == contentCommand){
			String teststring = cField.getString();
			findProtocols(teststring);
		}
		else if (c == backCommand){
			display.setCurrent(form);
			textbox = null;
		}
	}
	
	public void showAlert(String title, String message){
		Alert alert = new Alert(title, message, null, AlertType.ERROR);
		display.setCurrent(alert);
	}
	
	public void startApp(){
		display.setCurrent(form);
		
	}
	
	public void pauseApp(){
		
	}
	
	public void destroyApp(boolean condition){
		
	}
}