java-player-users

[Java-player-users] Problems with laserinterface

[kevinl <liu...@gm...>]

Hi all,
I don't know how to use the laserInterface, so I run the following code for
a try:
lsri = robot.requestInterfaceLaser (0, PlayerConstants.PLAYER_OPEN_MODE);
while(lsri.isDataReady());
	lnum=lsri.getData().getRanges_count();
	lsri.getData().getRanges();
	ldata=lsri.getData().getRanges();

I get the error of "NullPointerException". Could you advise me on how to use
the laserInterface? And I am confused with the method "public void
readData(PlayerMsgHdr header)" , how can I get a PlayerMsgHdr variable?

Thanks a lot,
kevin.

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Re: [Java-player-users] Problems with laserinterface

[Skuld <tan...@ho...>]

What is your version of JavaClient?

I don't work a lot on JavaClient, but I know that you have to call (directly
or not)
a function whose name is Read() (PlayerClient in the c++ native library), in
order to retrieve data from
Player/Stage, to fill up fields of your structure, and then you can reach
data by
functions like getRanges().
So your first call of getRanges, "lsri.getData().getRanges();", can't fill
these fields. It's useless.
Maybe you have to call readAll() (of the class PlayerClient in javaClient)
if you're not in threaded
mode, or call runThreaded(0,0) if you implemented the Runnable interface.
Those functions will call
an equivalent of Read.
I guess that "isDataReady" doesn't ask a reading from Player/Stage, but
only check if, in the most recent data retrieved, there is data about laser.
But you
still have to retrieve it.

If it doesn't work, check your "robot" creation. Maybe it's your nullpointer
error' source.

Do you know the name of the function which cause the error?


kevinl wrote:
> 
> Hi all,
> I don't know how to use the laserInterface, so I run the following code
> for a try:
> lsri = robot.requestInterfaceLaser (0, PlayerConstants.PLAYER_OPEN_MODE);
> while(lsri.isDataReady());
> 	lnum=lsri.getData().getRanges_count();
> 	lsri.getData().getRanges();
> 	ldata=lsri.getData().getRanges();
> 
> I get the error of "NullPointerException". Could you advise me on how to
> use the laserInterface? And I am confused with the method "public void
> readData(PlayerMsgHdr header)" , how can I get a PlayerMsgHdr variable?
> 
> Thanks a lot,
> kevin.
> 
> 

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Re: [Java-player-users] Problems with laserinterface

[Leo N. <leo...@gm...>]

If you get a "NullPointerException" you should also know which line it is
thrown from. I guess it's thrown from the "while(lsri.isDataReady());" as
lsri may be null if "robot.requestInterfaceLaser (0,
PlayerConstants.PLAYER_OPEN_MODE);" is unable to locate the laser interface.
Anyway try to get more info on the NullPointerException and post the whole
stacktrace if you need more help.

Bests
Leo


2009/4/10 Skuld <tan...@ho...>

>
> What is your version of JavaClient?
>
> I don't work a lot on JavaClient, but I know that you have to call
> (directly
> or not)
> a function whose name is Read() (PlayerClient in the c++ native library),
> in
> order to retrieve data from
> Player/Stage, to fill up fields of your structure, and then you can reach
> data by
> functions like getRanges().
> So your first call of getRanges, "lsri.getData().getRanges();", can't fill
> these fields. It's useless.
> Maybe you have to call readAll() (of the class PlayerClient in javaClient)
> if you're not in threaded
> mode, or call runThreaded(0,0) if you implemented the Runnable interface.
> Those functions will call
> an equivalent of Read.
> I guess that "isDataReady" doesn't ask a reading from Player/Stage, but
> only check if, in the most recent data retrieved, there is data about
> laser.
> But you
> still have to retrieve it.
>
> If it doesn't work, check your "robot" creation. Maybe it's your
> nullpointer
> error' source.
>
> Do you know the name of the function which cause the error?
>
>
> kevinl wrote:
> >
> > Hi all,
> > I don't know how to use the laserInterface, so I run the following code
> > for a try:
> > lsri = robot.requestInterfaceLaser (0, PlayerConstants.PLAYER_OPEN_MODE);
> > while(lsri.isDataReady());
> >       lnum=lsri.getData().getRanges_count();
> >       lsri.getData().getRanges();
> >       ldata=lsri.getData().getRanges();
> >
> > I get the error of "NullPointerException". Could you advise me on how to
> > use the laserInterface? And I am confused with the method "public void
> > readData(PlayerMsgHdr header)" , how can I get a PlayerMsgHdr variable?
> >
> > Thanks a lot,
> > kevin.
> >
> >
>
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>
>
>
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-- 
**************************************
Leonardo Nomdedeu Calvente
leo...@gm...

Re: [Java-player-users] Problems with laserinterface

[kevinl <liu...@gm...>]

Hi Skuld,
Thank you for your advice, I call runThreaded(-1,-1) before my code and I
can get the data now. And I'm sorry to reply your message so late.  And I am
confused why the fuction of runThreaded(-1,-1) will call an equivalent of
Read. Could you tell me why?

Thanks a lot,
kevin


Skuld wrote:
> 
> What is your version of JavaClient?
> 
> I don't work a lot on JavaClient, but I know that you have to call
> (directly or not)
> a function whose name is Read() (PlayerClient in the c++ native library),
> in order to retrieve data from
> Player/Stage, to fill up fields of your structure, and then you can reach
> data by
> functions like getRanges().
> So your first call of getRanges, "lsri.getData().getRanges();", can't fill
> these fields. It's useless.
> Maybe you have to call readAll() (of the class PlayerClient in javaClient)
> if you're not in threaded
> mode, or call runThreaded(0,0) if you implemented the Runnable interface.
> Those functions will call
> an equivalent of Read.
> I guess that "isDataReady" doesn't ask a reading from Player/Stage, but
> only check if, in the most recent data retrieved, there is data about
> laser. But you
> still have to retrieve it.
> 
> If it doesn't work, check your "robot" creation. Maybe it's your
> nullpointer error' source.
> 
> Do you know the name of the function which cause the error?
> 
> 
> kevinl wrote:
>> 
>> Hi all,
>> I don't know how to use the laserInterface, so I run the following code
>> for a try:
>> lsri = robot.requestInterfaceLaser (0, PlayerConstants.PLAYER_OPEN_MODE);
>> while(lsri.isDataReady());
>> 	lnum=lsri.getData().getRanges_count();
>> 	lsri.getData().getRanges();
>> 	ldata=lsri.getData().getRanges();
>> 
>> I get the error of "NullPointerException". Could you advise me on how to
>> use the laserInterface? And I am confused with the method "public void
>> readData(PlayerMsgHdr header)" , how can I get a PlayerMsgHdr variable?
>> 
>> Thanks a lot,
>> kevin.
>> 
>> 
> 
> 

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Re: [Java-player-users] Problems with laserinterface

[Skuld <tan...@ho...>]

^^

Sure I can.
As I told you in my first reply, you have to call the Read method to fill up
your structure's fields,
from a communication pipe with Player.

That is the code of the JavaClient (2.0.1 version, but all versions should
work the same.) 

    public void runThreaded (long millis, int nanos) {
        if (isThreaded) {
            System.err.println ("[PlayerClient]: A second call for
runThreaded, ignoring!");
            return;
        }
	    this.millis = millis;
	    this.nanos  = nanos;
	    isThreaded  = true;
	    this.start ();
	}

As you can see, when you call RunThreaded, you just set some special fields
before
launching the start method. I guess you know how works Threads in java, so
I'll just show you
the run method (which is called by the start method):

    public void run () {
        try {
            while (isThreaded) {
            	if (this.datamode == PLAYER_DATAMODE_PULL) {
        			this.requestData ();
                	while (read () != PLAYER_MSGTYPE_SYNCH && isThreaded);
            	} else
//            		while (is.available () != 0)
//                	while (read () != PLAYER_MSGTYPE_SYNCH && isThreaded);
            		read ();
            	
                if (millis < 0)
                    Thread.yield ();
                else
                    if (nanos <= 0)
                        Thread.sleep (millis);
                    else
                        Thread.sleep (millis, nanos);
            }
        } catch (InterruptedException e) { throw new PlayerException (e); }
//    	} catch (IOException e) { throw new PlayerException (e); }
    }

Do you understand? This function have a while's loop. This loop first wait
for data from Player,
and dispatch it in the structures's fields with a read() 's loop. There is
the call of the Read function.
(an equivalent to be meticulous, because Read function is available in C
library, but in Java,
read is a private function. You just can call it by readAll(), which does
the same things that the C one does,
and the simple read does too -but with verifications.)

So, in fact when you call RunThreaded, one Thread is specially created to
catch information from
Player and dispatch it into structures, for the other Thread (because
threads share memory.), so for your code,
so you doesn't have to call Read() anymore. And you still have informations
from Player.

Here it is !
I hope I was clear enough ^^ If I wasn't, tell me so.
Have a nice day!
Skuld


kevinl wrote:
> 
> Hi Skuld,
> Thank you for your advice, I call runThreaded(-1,-1) before my code and I
> can get the data now. And I'm sorry to reply your message so late.  And I
> am confused why the fuction of runThreaded(-1,-1) will call an equivalent
> of Read. Could you tell me why?
> 
> Thanks a lot,
> kevin
> 
> 

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Re: [Java-player-users] Problems with laserinterface

[kevinl <liu...@gm...>]

Hi Skuld,
Thanks very much.^_^
I get it. So the thread will keep calling the read() until yield() or
sleep().

Yours sincerely,
kevin.


Skuld wrote:
> 
> ^^
> 
> Sure I can.
> As I told you in my first reply, you have to call the Read method to fill
> up your structure's fields,
> from a communication pipe with Player.
> 
> That is the code of the JavaClient (2.0.1 version, but all versions should
> work the same.) 
> 
>     public void runThreaded (long millis, int nanos) {
>         if (isThreaded) {
>             System.err.println ("[PlayerClient]: A second call for
> runThreaded, ignoring!");
>             return;
>         }
> 	    this.millis = millis;
> 	    this.nanos  = nanos;
> 	    isThreaded  = true;
> 	    this.start ();
> 	}
> 
> As you can see, when you call RunThreaded, you just set some special
> fields before
> launching the start method. I guess you know how works Threads in java, so
> I'll just show you
> the run method (which is called by the start method):
> 
>     public void run () {
>         try {
>             while (isThreaded) {
>             	if (this.datamode == PLAYER_DATAMODE_PULL) {
>         			this.requestData ();
>                 	while (read () != PLAYER_MSGTYPE_SYNCH && isThreaded);
>             	} else
> //            		while (is.available () != 0)
> //                	while (read () != PLAYER_MSGTYPE_SYNCH && isThreaded);
>             		read ();
>             	
>                 if (millis < 0)
>                     Thread.yield ();
>                 else
>                     if (nanos <= 0)
>                         Thread.sleep (millis);
>                     else
>                         Thread.sleep (millis, nanos);
>             }
>         } catch (InterruptedException e) { throw new PlayerException (e);
> }
> //    	} catch (IOException e) { throw new PlayerException (e); }
>     }
> 
> Do you understand? This function have a while's loop. This loop first wait
> for data from Player,
> and dispatch it in the structures's fields with a read() 's loop. There is
> the call of the Read function.
> (an equivalent to be meticulous, because Read function is available in C
> library, but in Java,
> read is a private function. You just can call it by readAll(), which does
> the same things that the C one does,
> and the simple read does too -but with verifications.)
> 
> So, in fact when you call RunThreaded, one Thread is specially created to
> catch information from
> Player and dispatch it into structures, for the other Thread (because
> threads share memory.), so for your code,
> so you doesn't have to call Read() anymore. And you still have
> informations from Player.
> 
> Here it is !
> I hope I was clear enough ^^ If I wasn't, tell me so.
> Have a nice day!
> Skuld
> 
> 
> kevinl wrote:
>> 
>> Hi Skuld,
>> Thank you for your advice, I call runThreaded(-1,-1) before my code and I
>> can get the data now. And I'm sorry to reply your message so late.  And I
>> am confused why the fuction of runThreaded(-1,-1) will call an equivalent
>> of Read. Could you tell me why?
>> 
>> Thanks a lot,
>> kevin
>> 
>> 
> 
> 

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