Help with Mp3 player

[Crathes]

Hello

Just to start, I tried using the search engine but could not find a post with then answers i was looking for.

I am programming an Mp3 player for a school project, but i am a bit stuck.
At the moment i have a GUI layout with three buttons created in a button array and added to a panel by a loop.
I have two classes that implements runnable.
One of them fetches a file from a URL location on my pc, and get the player started.
The other class is supposed to stop the player.
I have two if sentences(?) that check which button i press.
When i press the play button, everything works as it is supposed to. But when i press the stop button, nothing happens.

Please help me :)

My plan is to add a playlist and some other stuff, but i have to get this stuff to work.

(tell me if you guys need me to post the code)
EDIT: posted code what i thought was relevant (no import stuff):

public class oppg2vaar2011Design extends JFrame implements ActionListener{

	ImageIcon playimg = new ImageIcon("src/playbutton1.gif");
	ImageIcon pauseimg = new ImageIcon("src/pausebutton1.gif");
	ImageIcon stopimg = new ImageIcon("src/stopbutton1.gif");
	
        private AdvancedPlayer player;
        private PlaybackListener listener;
	JPanel p1 = new JPanel();
	private GridLayout g1 = new GridLayout(1,3);	
	JButton btn[] = new JButton[3];

          oppg2vaar2011Design() {
		setSize(500,250);
		setTitle("MP3 Spiller");
		setDefaultCloseOperation(EXIT_ON_CLOSE);

		this.getContentPane().setLayout(new BorderLayout());
		this.getContentPane().add(p1);
		
		this.p1.setLayout(g1);
		
		// add buttons
		for (int i=0; i<btn.length;i++){
			btn[i]= new JButton();
			btn[i].addActionListener(this);
			btn[i].putClientProperty( "JButton.buttonType", "roundRect" ); 
			p1.add(btn[i]);
	         }
		//Sett ikon på knappene
		this.btn[1].setIcon(playimg);
		this.btn[2].setIcon(stopimg);
		
		}
	
	//Play thread, linked to play button in an if sentence
	class Playthr implements Runnable{ //Start player thread

		public void run() {
			try{
				URL url = new URL("file:///C://a.mp3");
				InputStream in = url.openStream();
                                player = new AdvancedPlayer(in);
				player.setPlayBackListener(listener); //added listener
				player.play();
			}
			catch(Exception e){
                                e.printStackTrace();
			}
		}
	}
	//stop thread linked to stop button in if sentence
	class Stopthr implements Runnable{ //Stop player thread

		public void run() {
			try{
				//player.stop();
                                player.close();
				
			}
			catch(Exception e){
                         e.printStackTrace();
			}
		}
	}
	

	public void actionPerformed(ActionEvent e) {
		
		Runnable runplay = new Playthr(); //get commands in Play thread
		Runnable runstop = new Stopthr();//get commands in stop thread
		Thread playthread = new Thread(runplay);//make play thread
		Thread stopthread = new Thread(runstop);//make stop thread
				for (int i=0; i<btn.length;i++) // using for loop to scan buttons
			if (btn[1]== e.getSource()){ // the button[i] is being pressed
				try{
					playthread.start();
				}
				catch(Exception ex){
                                        e.printStackTrace();

				}
			break;
			}
			else if (btn[0]== e.getSource()){ // the button[i] is being pressed
					try{
						playthread.interrupt();
						stopthread.start();
					}
					catch(Exception ex){
                                                e.printStackTrace();
					}
				}
		}

[Crathes]

Bump? I really need help guys :(
Is my post understandable? I'm asking because if it is, I'll have to try to explain my problem better.

[Solarsonic]

Why don't you start by handling your exceptions? Especially for blocks that you have problems with, like the block where you stop your player. Besides that, I don't see the if statements nor the stop() method or the AdvancedPlayer class.

[Crathes]

what do you mean handling the exceptions? Displaying them through a system.out.prinln?

This is the block that is supposed to stop the player:

class Stopthr implements Runnable{ //Stop player thread

		public void run() {
			try{
				player.stop();
				
			}
			catch(Exception e){
			}

It is supposed to run when i press button [0]. Thats at least what i tried in this if statement:

else if (btn[0]== e.getSource()){ // the button[i] is being pressed
					try{
						playthread.interrupt();
						stopthread.start();
					}
					catch(Exception ex){

					}

I try both interrupting the thread that is playing the mp3 file and i try starting the thread that stops the player.

The Advanced player is made further up in the code(i chose not to include that part, because its just a lot of declaring variables and stuff) through this code:

private AdvancedPlayer player;

[Solarsonic]

Do you know what exceptions are there for? There not just something you have to write, they tell you what's wrong when you have a problem like this (in other words, they're extremely useful). So yes, use e.printStackTrace() or System.out.println(e) for exceptions, especially when something is wrong in that block of code.

Why don't you add an ActionListener for your buttons? Here's one you can use for your stop button, so that when the button is pressed it executes the code within the actionPerformed() method.

ActionListener buttonListener1 = new ActionListener() {
public void actionPerformed(ActionEvent evt){
try{
playthread.interrupt();
stopthread.stop();
}catch(Exception e){e.printStackTrace();}
}
};
button[0].addActionListener(buttonListener1);

[Crathes]

Oh, ok... I hope i understand the error messages then ^^

The action listener for the buttons are added in the same loop that ads the buttons to a panel. Part of the code i didn't think was necessary.

I'll just add it to the OP

EDIT: added full code to OP

The error message from the stop button gives me the message "null". This means that i get no data when pressing the button?

[Solarsonic]

You ignored what I said twice. Add a e.printStackTrace() to your exception handling code for the block that stops your player. Then, tell me the error if any you get.

EDIT: Copy and paste the entire error here.

[Crathes]

No, I added an system.out.println to the exceptions. The message i got was "null"
Should i add both a system.out.println and an e.printStackTrace()?

[Fubarable]

No, I added an system.out.println to the exceptions. The message i got was "null"
Should i add both a system.out.println and an e.printStackTrace()?

I don't see any code in your catch blocks in the code you've posted above. And yes, you'll want to add e.printStackTrace(); in the catch blocks, not println.

[Crathes]

I don't see any code in your catch blocks in the code you've posted above. And yes, you'll want to add e.printStackTrace(); in the catch blocks, not println.

Oh, sorry... forgot to update the code up top.
Doing it now.

[Crathes]

The error message i got from e.printStackTrace() says:

java.lang.NullPointerException
at javazoom.jl.player.advanced.AdvancedPlayer.stop(Un known Source)
at oppg2vaar2011Design$Stopp.run(oppg2vaar2011Design. java:82)
at java.lang.Thread.run(Unknown Source)

[Fubarable]

The error message i got says:

java.lang.NullPointerException
at javazoom.jl.player.advanced.AdvancedPlayer.stop(Un known Source)
at oppg2vaar2011Design$Stopp.run(oppg2vaar2011Design. java:82)
at java.lang.Thread.run(Unknown Source)

Now we're getting somewhere. What line is line 82 of your file?

[Crathes]

Now we're getting somewhere. What line is line 82 of your file?

Just wait a sec... have no idea how i check line in eclipse. Have to download notepad ++.

[Fubarable]

Just wait a sec... have no idea how i check line in eclipse. Have to download notepad ++.

In Eclipse all you have to do is click on the exception.

[Crathes]

Great, thanks. Learning new stuff all the time :)

line 82:
player.stop();

can be found here:
class Stopthr implements Runnable{ //Stop player thread

public void run() {
try{
player.stop();

}
catch(Exception e){
e.printStackTrace();
}

[Fubarable]

Then player is null when you try to call the stop method on it above. Now you've got to trace back into your code and figure out why.

[Crathes]

So, when i press the stop button, the player is already null?
How can that be? I hear the music playing.

[Fubarable]

So, when i press the stop button, the player is already null?
How can that be? I hear the music playing.

You likely have more than one Player variables, one null, the other not. This can happen for instance if you have created more than one oppg2vaar2011Design objects.

[Crathes]

Right at the start i have make the player variable through this:
private AdvancedPlayer player;

further down i do this to get the file the player is supposed to play:
InputStream in = url.openStream();
player = new AdvancedPlayer(in);

could that second new AdvancedPlayer mess stuff up?

[Fubarable]

Right at the start i have make the player variable through this:
private AdvancedPlayer player;

further down i do this to get the file the player is supposed to play:
InputStream in = url.openStream();
player = new AdvancedPlayer(in);

could that second new AdvancedPlayer mess stuff up?

That is only one AdvancedPlayer object -- you only use the new keyword once.

How many times do you call new oppg2vaar2011Design()?