KEY events in MIDlets

Hello all,
I am basically new to J2ME MIDP development and also new to this
forum. So apologies if this has already been covered or turns out to
be a stupid question :) Here goes:
I am trying to develop a MIDlet where I have a Form to accept certain
values from the user. This is fairly straightforward and is easy to
create with the high level Form a and TextField objects.
Now, I wish to add a functionality to my MIDlet, in which, the user
can press a specific key.. say the "Select" key or the "Call" key.. at
any time during the form to start another thread of operation which
performs something totally different... say for example, the user is
entering values into the form and in between somewhere he presses this
specific key and the phone start playing music. I hope you get my
point.
Basically I want to listen for key pressed or key held events on a
Form object. Now I understand that Key events can be found only on the
low-level Canvas based UIs. So is it possible to do it with Screen class
elements..?
Thanks,
Nik

You can try to use a CustomItem. What events will be delivered to the custom item depends on the implementation, though. Also these events will be only delivered when the CustomItem is focused.
Have a look at the J2ME Polish GUI for using CustomItems for MIDP/1.0 devices as well.
http://www.j2mepolish.org
Best regards,
Robert

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Unable to find Key Events when there are multiple Commands

Hi,
I've developed a simple J2ME Appln containing 3 commands
for ex- Exit,Help and Info(all with same priority).
As there are 3 commands, Exit command is present at the left and the other two namely Help and Info have been listed under Menu and this Menu command is presented at the right.
My MIDlet class has extened MIDlet and implemented CommandListener. Using CommandAction(), I'm able to generate action for Command press and i've also created a nested class which extends Canvas so, using keyPressed and keyReleased, I'm able to find the Key Press Events.
Now, my appln needs to find just the key press events. After i press the Menu command, the two commands namely Help and Info are listed. In tht screen, I need to find out whether any other key events are being generated but my keyPressed and keyReleased are not being called.
Please provide me solution ASAP.

I'm going to make a few assumptions:
1. The menu you're describing is the automatically generated one caused by having more than two commands.
2. The subclass of Canvas is the currently active Displayable (otherwise you won't get any key events at all).
If this is the case (and someone correct me if I'm wrong), key events are being handled by the phone's subsystem to drive the menu, which means there's no way to get them. The way I've approached this kind of problem is to create my own menu painting and handling code and incorporated it into the Canvas. Then, make one Command called 'Menu' and have it invoke your custom menu code.
I realise this isn't an ideal solution, but it's something.

Simulation of Key events ????

Hello there,
I would like to simulate a succession of pressed key events in order to trace the mem. allocations of a midlet under constant setup.
How could I trigger those events from my application ? which low-level method should I called ?
I tied to found myself in the API and also to 'google' for a solution, but so far it wasn't successful....
Any idea will be welcome !
Thanks

Hi khsay!
If you are using Windows as OS you can never get your application to run in realtime, you have to use LV Realtime to do that.
If you use the event structur i a while loop you get as close as possible, i think.
I have modified your caps.vi so it reacts on booth CAPS button and CAPS key on the keyboard.
Hope this helps!
Regards
/Thomas
Attachments:
caps[1].vi ‏41 KB

Macbook misses some key events for a few seconds

I have noticed that for last two months or so something strange happens to my Retina MBP. Once in a couple of days it stops responding to some key events. It is like it handles only one keypress out of 4-5. Nothing seems to be wrong with the keyboard and it is not about a particular key or keys. And about 10-15 seconds later everything goes back to normal. I do not see any suspicious messages in the logs, the computer is connected to the power supply...It happens just by itself in the middle of the day, when I am typing.
Almost looks like some interrupts get lost by the system while it is busy with something else. But I have checked the load level and running processes - nothing interesting there....And whatever it is - it happens during a very short period of time.

Hi,
No, I have not returned my MBP yet. In fact, I would rather avoid doing this unless I am convinced if it is a hardware issue. And I do believe it is not. Just recently I have spent some time investigating it and I have found very stroing correlation between the moments when this happens and these messages in the kernel log:
Jan 13 10:49:54 mbp-wifi kernel[0]: Sandbox: sandboxd(96471) deny mach-lookup com.apple.coresymbolicationd
Jan 13 10:54:31 mbp-wifi kernel[0]: Sandbox: sandboxd(96499) deny mach-lookup com.apple.coresymbolicationd
Jan 13 10:54:31 mbp-wifi.home sandboxd[96499] ([96497]): mdworker(96497) deny mach-lookup com.apple.ls.boxd
Jan 13 10:54:31 mbp-wifi.home sandboxd[96499] ([96498]): mdworker(96498) deny mach-lookup com.apple.ls.boxd
Jan 13 10:56:32 mbp-wifi.home sandboxd[96504] ([96503]): mdworker(96503) deny mach-lookup com.apple.ls.boxd
Jan 13 10:56:32 mbp-wifi.home sandboxd[96504] ([96502]): mdworker(96502) deny mach-lookup com.apple.ls.boxd
And I have also noticed that my Spotlight database gets reconstructed too often, which means it gets corrupted.
From all this I conclude that it is most likely the software issue and it seems to be linked to spotlight. I saw people reporting similar things. So now I am researching on how to fix it without disabling the spotlight.
In general, I believe that the quality of Apple software is going down, it is not like 4-5 years ago And Apple does seem to care less and less about it.
If in your case it happens all the time, not just once in a while, and you see that a particular key has problems - it is possible that we are talking about the different issues and yours might be really about the keyboard.

Detect key events on anything

If I have a JFrame with many components on it, how do I detect if a key is pressed, without having to add a listener to every component? For example, how can I check for the escape key being pressed, but not having to have componentN.addKeyListener(this); for everything?
Thanks
US101

The correct way to collect the key events is the following:
from java 1.2 to java 1.3 use the FocusManager. This class can be found in the javax.swing package. You would then need to extend the DefaultFocusManager and override specific behavior.
for java 1.4 use the KeyBoardFocusManager. This class can be found in the java.awt package.
Please see the following for a better explanation:
http://java.sun.com/j2se/1.4/docs/api/java/awt/doc-files/FocusSpec.html
Thanks for your time,
Nate

Catching key events in application

I have a JFrame with a JDesktop containing lots of JInternalFrame with various of components such as JTextFields etc.
Now, i want to have a "main" listener that will catch key events no matter which component that has focus. For example pressing CTRL+A should produce something in the application no matter which component that has focus.
How do I implement this in an easy way?

It doesnt seem to work to add a KeyListener to the JFrame...
this.addKeyListener(new KeyAdapter(){
               public void keyTyped(KeyEvent e){
                    System.out.println("KeyTyped()");
               public void keyPressed(KeyEvent e){
                    System.out.println("KeyTyped()");
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Associating key events to a TextBox

Hello All!
Can anybody tell me how to associate key events with a TextBox? Something like when a certain key is pressed and released, a certain combinations of characters is inserted e.g. =-)
I am trying to develop a simple application that allows users to type text with non-English characters, e.g. Russian and for that I have created a canvas and I am using key events i.e. KeyPressed and KeyReleased methods. Using a canvas is a bit insufficient because users cannot move the cursor freely through the text.
I have read on te web that I can create a CustomeItem and override the KeyPressed methods but I could not do it; I could not find any simlar code example.
Can anybody help me by providing me with a simple example or suggesting me an alternative way?
Many thanks in advance

{color:#008080}*Hello again!*
I managed to create a CustomItem that overrides KeyPressed method, but now I am having difficulties making my textBox reacts to my keyPressed method.
The early version of this CustomeItem overrides the KeyPressed method by assigning each key to a certain collection of chars. When a key is pressed, a string of these chars is drawn on the Canvas, which works fine. Now because I want to be able to edit the text, e.g. delete a certain char in the middle of the string, I want to use a TextBox or a TextField. The current problem is that my TextBox does not react to my key presses the way I want (I used setString() method); it reacts to the original key presses which print the original chars (from A through to Z and 1 through to 9).
Is it possible to set the contents of a TextBox or TextField depending on my key presses? Could you suggest me an alternative way?
Many thanks in advance!!{color}

Object Movement with Key Events

Hi everybody!
Im trying to move an object over the screen with keyboard buttons. The problem I have come across with is that I would like to use the right button to move right, up button to move forward, etc. but I cant push, for example, right and up buttons at the same time to make a diagonal movement. How can I solve this?
Thank you and regards.

I added key events to a sequence and than check them in the program.
Something like this:
class Car extends CustomNode {
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        ImageView {
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            x: -w
            y: -h
            image: Image { url: "{__DIR__}car.png"}
            onKeyPressed: function( e: KeyEvent ) {
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                    ds = 2.0;
                }else if(e.code == KeyCode.VK_DOWN){
                    ds = -2.0;
                }else if(e.code == KeyCode.VK_LEFT){
                    da = -1.0;
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Binding Mouse and Key Events.

Hi,
When a user clicks the Ctrl + V the data from the clipboard
is pasted into the user area. Instead of using this can we do it
using a mouse click. For now, I am planning to bind the event code
of these combinations (CTRL + V == 86) to the mouse click. But when
I tried this I am unable to bind this key event to the mouse event.
Can anyone help me out for getting out of this problem.
Regards,
eodC.

No, it isn't.
Kind regards,
Levi

How to consume key events

I would like to create a subclass of TextBox that only allows numeric input. My idea was to provide my own onKeyType() handler and consume any key events that do not correspond to digits. However, I can't find any way to consume key events from further processing. How do I do this?
Are there any other suggestions how to accomplish the task of providing your own filter concerning valid key input?
/Bengt

I also wanted a kind of validators for the TextBox class of JavaFX. So I've tried solving the problem using the SwingTextField class and some Java APIs. The following is my code for a SwingTextField accepting only digits, but I do want it to be much simpler.
import java.awt.AWTEvent;
import java.awt.event.AWTEventListener;
import java.awt.event.KeyEvent;
import java.awt.Toolkit;
import javafx.ext.swing.SwingTextField;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javax.swing.JComponent;
class DigitKeyEventHookListener extends AWTEventListener {
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    public override function eventDispatched( event:AWTEvent):Void {
        if (event.getSource().equals(source)) {
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            var isDigit = false;
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           if ((KeyEvent.VK_0 <= keyCharacter) and (keyCharacter <= KeyEvent.VK_9)) {
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            if ((code ==KeyEvent.VK_LEFT) or (code ==KeyEvent.VK_RIGHT)) {
                isDigit = true;
           if (not isDigit) {
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function createSwingTextField() : SwingTextField{
    var field = SwingTextField {
        columns:12
    var listener = DigitKeyEventHookListener{
        source: field.getJTextField()
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Stage {
    title: "Digit Box"
    width: 200
    height: 80
    scene: Scene {
        content: createSwingTextField()
}

No key event when compose keys are pressed

I am supporting a legacy application for Sabre which maps some of the keys differently. For example, on a French keyboard the Compose key which is used to put a ^ on top of the vowel characters is to be remapped to produce a special character called a "Change Character" that has a special use for reservation agents that use Sabre
The problem is, the first time you press the ^ compose key there is no key event apparently because the VM figures it doesn't yet know what key to report, it is expecting you to press a character such as 'o' and then you get an 'o' with a '^' on top of it.
If you press the ^ compose key a second time, you get the following key events:
keyPressed
keyTyped
keyTyped
keyReleased
On the screen you will see two ^ characters appear. Currently I remap the ^ character to the "Change Character", and I suppress the second keyTyped event so that I only get one character. The problem is that the user ends up having to press the key twice to get one "Change Character."
I have no fix for this problem because there is no key event produced when they press the ^ compose key the first time.
By the way, this behavior appears to have been introduced with jdk 1.3. The older jdk did produce a key event the first time you pressed the compose key. I would expect that this behavior was considered to be a bug and was fixed in jdk 1.3.
Is there some other way to detect when the user presses a compose key? If not, is it possible for future jdk releases to report a keyPressed event when a compose key is pressed? This event would not cause a character to appear on the screen, but would allow programs to detect when the compose key is pressed.
There is already a key on the French keyboard that behaves this way. It is the key to the left of the '1' key and it has the pipe symbol on it. If you press Shift plus this pipe key, no character is produces but a keyPressed event with a keycode of 222 is produced. I merely point this out to show that there is a way to report key events whithout producing output on the screen.
Thanks, Brian Bruderer

I don't know if this actually helps, but it seems that you can bind an Action to a dead key like the circumflex of the French keyboard
Keymap keymap = textPane.addKeymap("MyEmacsBindings", textPane.getKeymap());
Action action = getActionByName(DefaultEditorKit.beginAction );
KeyStroke key = KeyStroke.getKeyStroke(KeyEvent.VK_DEAD_CIRCUMFLEX);
keymap.addActionForKeyStroke(key, action);I saw this on a Swing tutorial and modified it slightly. Have a look at it :
http://java.sun.com/docs/books/tutorial/uiswing/components/generaltext.html
Chris

2nd JFrame at Full Screen not registering key events

I've written an application that launches other applications distributed as JARs with a particular method (replacing the main method). These other applications run at full screen.
Whilst I have got these other applications to work in that they display correctly and do everything else, I require them to register key events. If I run these applications on their own (i.e. having not been launched by the primary application) then the key events are processed correctly. However when they are launched from the primary application the key events are not registered.
I have tried requesting focus from the full screen JFrame but it doesn't seem to be able to.
Any ideas?

Possible that the keystrokes are really being trapped by the other gui, which stops registering them when it's not visible.
IF that's the case, you'll need to re-design your keyboard trap as part of the second JFrame, wholly independent of the original JFrame or originating app. Also, it may be thread-starved i.e. operating off the originating program, which thread may be stopping when it has no focus.
That's all the ideas I have.

Is using key events really that hard?

I am trying to implement a keyListener for my application, and it seems
way harder than it should be. My application is simple: A JFrame
with one button and one JPanel upon which I draw. When I click
in the JPanel and type, I want things to happen.
After much looking, it seems I have to not only implement KeyListener,
but also MouseListener, so when the mouse enters I can call
requestFocusInWindow().
That seems to work sometimes, but not when I leave and come back,
and not always when the application first appears.
So do I also have to implement FocusListener?
Why is this so hard to do? MouseListener is very easy to implement,
but KeyListener seems to be a huge pain in the butt.
Can someone point me to a simple tutorial or example that just
has a few swing elements, and processes key events?
I feel like with Java I often try enough things until it finally works,
and never really understand why, and what it was that fixed it.
The documentation and API does not fully describe everything one
needs to know to use the API "properly". Am I the only one frustrated
by this? I have programmed in Java/Swing for years, and JUST LAST
WEEK discovered that when implementing paint in swing, one should
override paintComponent and not paint. But then why does overriding
paint usually work? There are too many quirks in Java that let you
get away with doing things wrong, and then suddenly, your application
is broken. It wouldn't be so bad if the API was more clear on some of
these suble issues.
Thanks,
Chuck.

How to Use Key Bindings

Lag on key press (key event)

Hello, I am currently working on a simple game in Java. I've used Java's Key_Pressed in Key Event to control a ship moving back and forth with the up and down keys. I've noticed that when a key is pressed there is a short pause before the ship actually moves. What can I do to avoid this pause?

The "repeat rate" for holding a key down is controlled by the OS.
You should not be relying on multiple KeyEvents to move your component as the repeat rate will vary from machine to machine. Actually you should not be using KeyEvents anyway you should be using [url http://java.sun.com/docs/books/tutorial/uiswing/misc/keybinding.html]Key Bindings
On keyPressed binding you would start a Timer and then on keyReleased you stop the Timer. You can then control the interval at which the Timer fires so you game will be consistent on all machines.

Plz tell me motrola support repeated key events.

Plz tell me about my this ancient problem that if some device support repeated key event than tell me its name and also provide a link to download it.
moreover also tell me about this strange content type:-
Here i have content type which is strange for me :- response.setRequestProperty("Content-Type","application/x-www-form-urlencoded") plz tell me either it will ok if i want to display some other language;
i want internationalization and want to set utf-8 but now tell me for what purpose is above content type and what would be its alternative. thanx

See http://www.kobjects.org/devicedb/ for which devices do and don't support key repeat events.
Application/x-www-form-urlencoded is defined at
http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4.1
You can use application/x-www-form-urlencoded with UTF-8 provided that the server is expecting UTF-8 encoded bytes. However, I don't think many MIDP implementations support String.getBytes("UTF-8") so you may be stuck with doing the UTF-8 encoding yourself.
If you control the server, you may want to instead use DataOutput.writeUTF() from the client and DataInput.readUTF() from the server. Another alternative is to use XML, where you can employ character references for non-US-ASCII characters.

KEY events in MIDlets

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