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J2ME Novice: Screen Navigation?

How do you navigate between screens in J2ME? I would like to navigate to the
next screen using the default emulator in KToolbar. Here is a snippit of my
commandAction method:
public void commandAction(C ommand c, Displayable s) {
if (c == mMenuCommand)
{
mMenuForm = new Form("SampleMID let");
final String[] menuItems = { "Games" , "Calculator ", "Alarm Clock" };
final List list = new List("Select a Item", List.IMPLICIT, menuItems, null);

final Command nextCommand = new Command("Next", Command.SCREEN, 0);
Command quitCommand = new Command("Quit", Command.SCREEN, 0);
list.addCommand (nextCommand);
list.addCommand (quitCommand);
list.setCommand Listener(new CommandListener ()
{
public void commandAction(C ommand c, Displayable s)
{
if (c == nextCommand || c == List.SELECT_COM MAND)
{
int index = list.getSelecte dIndex();
System.out.prin tln("Your selection: " + menuItems[index]);

// Move on to the next screen. Here, we just exit.
notifyDestroyed ();
} else notifyDestroyed ();
}
});
Display.getDisp lay(this).setCu rrent(list);
}

if (c == mExitCommand) notifyDestroyed ();
}

Thanks!
Gilgantic
Jul 17 '05 #1
7 9133
gilgantic wrote:
How do you navigate between screens in J2ME?


See the Javadoc for javax.microedit ion.lcdui.Displ ay.setCurrent for more
information.

--
Darryl L. Pierce <mc******@myrea lbox.com>
Visit the Infobahn Offramp - <http://bellsouthpwp.ne t/m/c/mcpierce>
"What do you care what other people think, Mr. Feynman?"
Jul 17 '05 #2
gilgantic wrote:
How do you navigate between screens in J2ME? <snip>


Sorry, I didn't read your entire message previously. You have to explicitly
tell the Display what the Displayable is that you want to show. There's no
way in the MIDP to tell the VM what the screens are and in what order they
should be displayed.

--
Darryl L. Pierce <mc******@myrea lbox.com>
Visit the Infobahn Offramp - <http://bellsouthpwp.ne t/m/c/mcpierce>
"What do you care what other people think, Mr. Feynman?"
Jul 17 '05 #3
"Darryl L. Pierce" <mc******@myrea lbox.com> wrote in message news:<d9******* *************** ********@free.t eranews.com>...
gilgantic wrote:
How do you navigate between screens in J2ME? <snip>


Sorry, I didn't read your entire message previously. You have to explicitly
tell the Display what the Displayable is that you want to show. There's no
way in the MIDP to tell the VM what the screens are and in what order they
should be displayed.


Well are there any online examples of an entire application. The ones I have
seen just have minimum amount of navigation. I will check into the javadoc
for the Display class.
Jul 17 '05 #4
gilgantic wrote:
> How do you navigate between screens in J2ME? <snip>


Sorry, I didn't read your entire message previously. You have to
explicitly tell the Display what the Displayable is that you want to
show. There's no way in the MIDP to tell the VM what the screens are and
in what order they should be displayed.


Well are there any online examples of an entire application. The ones I
have
seen just have minimum amount of navigation. I will check into the
javadoc for the Display class.


There's not really much to it. In your commandAction() method, you
determine which command the user selected and then programmaticall y set the
next Displayable by calling:

Display.getDisp lay([reference to your MIDlet]).setCurrent([the Displayable])

There's no underlying system for registering Displayables or mapping them,
though such would be a cool side project. :)

--
Darryl L. Pierce <mc******@myrea lbox.com>
Visit the Infobahn Offramp - <http://bellsouthpwp.ne t/m/c/mcpierce>
"What do you care what other people think, Mr. Feynman?"
Jul 17 '05 #5
Ok, I tried this with the following code below, but got the exception listed
below ..

code snippet from MyMidlet
=============== ===============
public void commandAction(
Command c, Displayable d ){
if (c == exitCommand) exitMIDlet();
if (c == selectCommand)
{
Display.getDisp lay(new HelloMIDlet()). setCurrent(d);
}
}

exception during selectCommand
=============== ===============
java.lang.Secur ityException: Application not authorized to access the restricted API

at com.sun.midp.se curity.Security Token.checkIfPe rmissionAllowed (+40)
at com.sun.midp.se curity.Security Token.checkIfPe rmissionAllowed (+7)
at com.sun.midp.mi dletsuite.MIDle tSuiteImpl.chec kIfPermissionAl lowed(+8)
at com.sun.midp.mi dlet.MIDletStat e.<init>(+66)
at javax.microedit ion.midlet.MIDl etProxy.<init>( +5)
at javax.microedit ion.midlet.MIDl et.<init>(+13)
at HelloMIDlet.<in it>(+4)
at MyMIDlet.comman dAction(+27)
at javax.microedit ion.lcdui.Displ ay$DisplayAcces sor.commandActi on(+284)
at javax.microedit ion.lcdui.Displ ay$DisplayManag erImpl.commandA ction(+10
at com.sun.midp.lc dui.DefaultEven tHandler.comman dEvent(+68)
at com.sun.midp.lc dui.AutomatedEv entHandler.comm andEvent(+47)
at com.sun.midp.lc dui.DefaultEven tHandler$Queued EventHandler.ru n(+250)

"Darryl L. Pierce" <mc******@myrea lbox.com> wrote in message news:<ef******* *************** ********@free.t eranews.com>...
gilgantic wrote:
> How do you navigate between screens in J2ME? <snip>

Sorry, I didn't read your entire message previously. You have to
explicitly tell the Display what the Displayable is that you want to
show. There's no way in the MIDP to tell the VM what the screens are and
in what order they should be displayed.


Well are there any online examples of an entire application. The ones I
have
seen just have minimum amount of navigation. I will check into the
javadoc for the Display class.


There's not really much to it. In your commandAction() method, you
determine which command the user selected and then programmaticall y set the
next Displayable by calling:

Display.getDisp lay([reference to your MIDlet]).setCurrent([the Displayable])

There's no underlying system for registering Displayables or mapping them,
though such would be a cool side project. :)

Jul 17 '05 #6
Peace to Darryl and Gilgantic!

I'm not sure what you really mean by Screen Navigation, but if you
mean being able to use the extra buttons such as those on the Nokia
9210i, I did try using the following app, which is the first I tried
to adapt from the provided SDK:

import com.symbian.dev net.crystal.awt .*;
import com.symbian.epo c.awt.*;
import java.awt.*;

class app1 extends CFrame {

EikCommandButto nGroup buttons;
final static int TBUTTON1 = EikCommandButto nGroup.BUTTON1;
final static int TBUTTON2 = EikCommandButto nGroup.BUTTON2;
final static int TBUTTON3 = EikCommandButto nGroup.BUTTON3;
final static int TBUTTON4 = EikCommandButto nGroup.BUTTON4;

public static void main (String args[]) {
new app1();
}

public app1() {
buttons = new EikCommandButto nGroup();
setTitle("Title ");
add(buttons);
buttons.setText (TBUTTON1,"1");
buttons.setText (TBUTTON2,"");
buttons.setText (TBUTTON3,"3");
buttons.setText (TBUTTON4,"Clos e");
buttons.addCBAL istener(new CBAListener() {
public void cbaActionPerfor med (CBAEvent e) {
if (e.getID()==TBU TTON4) {
System.exit(0);
}
}
}
);
}
}

You'll have to download the additional Symbian classes but its worth
it if you can get those buttons to work the magic for you.

"Darryl L. Pierce" <mc******@myrea lbox.com> wrote in message news:<ca******* *************** ********@free.t eranews.com>...
gilgantic wrote:
<snip>
if (c == selectCommand)
{
Display.getDisp lay(new HelloMIDlet()). setCurrent(d);
}

<snip>

No. You can't instantiate a MIDlet to do this job. You have to have a
reference to the currently running MIDlet when attempting to get a Display
reference. The usually pattern is to have a setCurrent(Disp layable) API in
your MIDlet class and set displays that way:

public class FooMIDlet extends MIDlet
{
private static FooMIDlet instance = null;

public FooMIDlet()
{
instance = this;
}

// ....

public static void setCurrent(Disp layable screen)
{
Display.getDisp lay(instance).s etCurrent(scree n);
}
}

Jul 17 '05 #7
From the examples I've seen, and what I've done personally, you should have
a class
that derives from midlet. Create a member variable of type Display in this
class, and
in the StartApp method of your derived class just set the display variable.
Now you always
have access to the display. I think creating a new Midlet inside a midlet
already running might be
your problem, but I'm new to this as well, so I'm not sure about that.

Code

public class Driver extends MIDlet {
Display m_display;
Driver {}
protected void startApp( ) {
m_display = Display.getDisp lay( this );
}
}

Now just pass the m_display variable whenever you need access to the
display. Hope this helps.

Brandon
"gilgantic" <gi*******@yaho o.com> wrote in message
news:d6******** *************** ***@posting.goo gle.com...
Ok, I tried this with the following code below, but got the exception listed below ..

code snippet from MyMidlet
=============== ===============
public void commandAction(
Command c, Displayable d ){
if (c == exitCommand) exitMIDlet();
if (c == selectCommand)
{
Display.getDisp lay(new HelloMIDlet()). setCurrent(d);
}
}

exception during selectCommand
=============== ===============
java.lang.Secur ityException: Application not authorized to access the restricted API
at com.sun.midp.se curity.Security Token.checkIfPe rmissionAllowed (+40)
at com.sun.midp.se curity.Security Token.checkIfPe rmissionAllowed (+7)
at com.sun.midp.mi dletsuite.MIDle tSuiteImpl.chec kIfPermissionAl lowed(+8)
at com.sun.midp.mi dlet.MIDletStat e.<init>(+66)
at javax.microedit ion.midlet.MIDl etProxy.<init>( +5)
at javax.microedit ion.midlet.MIDl et.<init>(+13)
at HelloMIDlet.<in it>(+4)
at MyMIDlet.comman dAction(+27)
at javax.microedit ion.lcdui.Displ ay$DisplayAcces sor.commandActi on(+284)
at javax.microedit ion.lcdui.Displ ay$DisplayManag erImpl.commandA ction(+10
at com.sun.midp.lc dui.DefaultEven tHandler.comman dEvent(+68)
at com.sun.midp.lc dui.AutomatedEv entHandler.comm andEvent(+47)
at com.sun.midp.lc dui.DefaultEven tHandler$Queued EventHandler.ru n(+250)

"Darryl L. Pierce" <mc******@myrea lbox.com> wrote in message

news:<ef******* *************** ********@free.t eranews.com>...
gilgantic wrote:
> > How do you navigate between screens in J2ME? <snip>
>
> Sorry, I didn't read your entire message previously. You have to
> explicitly tell the Display what the Displayable is that you want to
> show. There's no way in the MIDP to tell the VM what the screens are and> in what order they should be displayed.

Well are there any online examples of an entire application. The ones I have
seen just have minimum amount of navigation. I will check into the
javadoc for the Display class.


There's not really much to it. In your commandAction() method, you
determine which command the user selected and then programmaticall y set the next Displayable by calling:

Display.getDisp lay([reference to your MIDlet]).setCurrent([the Displayable])
There's no underlying system for registering Displayables or mapping them, though such would be a cool side project. :)

Jul 17 '05 #8

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