Develop Reference

Keycode event for BACKSPACE in JavaFx

I am doing a project in JavaFX, using Java 8 and Gluon scenebuilder. I want to detect when backspace is pressed inside a TextField. This is the code I am using:
public void keyPressed(KeyEvent kEvent) {
if (kEvent.getCode() == KeyCode.BACK_SPACE) {
System.out.println("Backspace pressed");
}
This code is inside the controller file, called FXMLDocumentController, which controls the GUI xml file FXMLDocument. You can see from the image below the function is called whenever a key is typed inside TextField. This works with all the letters/numbers, but not with backspace.
Gluon scene builder settings
Theoretically it should work, but it doesn't.
How can I manage typing of the backspace button?
Edit:
Notice that putting this exact function on the root of the elements, on the "Window itself" (which is the AnchorPane) works. The problem is with reading the pressing of the backspace inside the TextField. You can see in the image below where I've put the function:
On the window backspace's detecting works

You should use your keyPressed method in either on key pressed or on key released.
In the Docs, it states that:
No key typed events are generated for keys that don't generate Unicode
characters (e.g., action keys, modifier keys, etc.).
Backspace is consider an Action Key.

In the screenshot of your SceneBuilder I can see you are referencing the keyPressed(KeyEvent kEvent) controller method with On Key Typed not On Key Pressed.
For events of KeyEvent.KEY_TYPED the value of getCode() is always KeyCode.UNDEFINED.
Edit: I came back to this answer and reread your question. I want to clarify something but what I said above is still correct.
In your edit you mention the "exact" same setup works with the AnchorPane but when looking at your screenshot there are some differences. For your AnchorPane you have the controller method referenced for all three types: On Key Pressed, On Key Released, and On Key Typed.
This means that the method should be called up to 3 times for each key stroke (when the events reach the AnchorPane). Once when pressed, once for typed (if the key is capable of sending typed events - see the answer by Sedrick for clarification), and then once for released. Because of this, the method will work for the pressed and released events, but it won't work for the typed events.
In other words, the reason your code works for the AnchorPane but not the TextField is because you configured it correctly for the AnchorPane but not the TextField.

Is there a way to fire a method from the press of the convenience key using android?

Is it possible to have my android application start a method from pressing of the convenience key when the application in focus?
On my phone the convenience key is a button located on the right hand side of the phone. I would like to be able to know if the user presses any of the buttons on the phone, even the volume would work.

You are welcome to override onKeyDown() on your Activity and watch for a KeyEvent of interest. Note that not every key in the KeyEvent JavaDocs is accessible this way (e.g., power). Also note that it is possible that some specific View that is aware of these keys might consume the event first, though that is relatively unlikely for anything that matches your description of a "convenience key".

Using the Keyboard "ContextMenu" button in Java

In the application I'm working on I'd like to listen for when the keyboard's context menu (right click) button is pressed.
Just to be clear, I'm talking about the button between Alt Gr and Ctrl on the right of the spacebar. I realise it is not on all keyboards (older, mac's etc), but I know that all of the keyboards which will be using this application will have the button.
I'd like to know if there is a simple KeyEvent or any other method for knowing when it has been pressed.
Thanks,
Dave

To echo #Thijs Wouters' answer, (a) this is always a great way to figure out what key codes are associated with what keys in Java, and (b), this key code for the context menu, 525, is 20D in hexadecimal, and is defined in Java (since 1.5) as
KeyEvent.VK_CONTEXT_MENU
for ease of code reading.

You can check the key code when a key is pressed. The key code of the context menu key is 525.
You can check this for yourself:
public void keyPressed(KeyEvent e) {
System.out.println(e.getKeyCode());
}

regain focus after java.awt.Robot.keyPress()/mousePress()

I writing an application which controls another application by using the keyboard only. To more concrete, the application simulates key presses and mouse clicks when a certain key is pressed on the keyboard. For example, pressing on the 'x' key simulates a mouse click on the [X] in the rop right corner, followed by a little sleep of 2 seconds and an 'enter' to confirm the exit dialog. Pretty easy. I am developing this application in Java.
Sending a key press or a mouse click is very easy with java.awt.Robot. I am facing one little problem. Say I have configured a key which will click somewhere on the screen. The problem is that consecutive key presses aren't catched anymore, as my application lost its focus caused by the mouse click outside it's window.
My question now is: what is the best way to be sure that my main application keeps the focus? Is there a way to focus my application again after the key presses and mouse clicks are sent out? Is there a better way?
Thanks in advance.

If your application lost the focus. because you or your Robot clicked to somwhere else, the Robot must click on the application again before sending a new key. In c/c++ you could force the focus to the application (a non-trivial task), not in Java!

You might want to take a look at Component.requestFocus() to see if can do what you want.
Be aware however that window focusing has very platform dependent behaviour, so you will probably need to do quite a bit of testing to ensure that your code does what you want in all circumstances.

I managed a way to prevent applications from losing all focus in Java.
By placing a WindowFocusListener on the frame (or dialog) and calling setVisible(false) followed by setVisible(true) in windowLostFocus the component will re-appear as soon as it is dissapears (not the prettiest solution but it does work).
By then calling component.requestFocus() your robot should be able to continue where it left off

J2ME: How to press keypad programmatically?

Is it possible to press keypad programmatically so that number for the key pressed shows on the screen? See the screenshot below for more explanation please:
Details:
Nokia N70
CLDC 1.1
MIDP 2.0

How you approach it will depend on what you want to achieve.
You can quite easily simulate pressing keys on a Canvas, by calling your Canvas's keyPressed(), keyReleased() and keyRepeated() methods directly.
This could be good for testing a canvas-based game, ensuring a given state is entered when certain keys are pressed on the canvas.
However, this won't allow you to control any form-based interaction, or native prompts. So you can't start the MIDlet, navigate through a LCDUI Form or List, accept a native security prompt, or edit a native TextBox. You'd need to use an emulator and some form of test scripting framework which simulates keypresses, such as Eggplant.

if you want to mimicking the keypressed process, just call the keypressed with the int of key as argument, for example keyPressed(-8);
Or are you trying to display the key number in the screen ?