Search code examples
javajtextfieldkeylistenerkeyevent

How to create a KeyEvent


When i create the KeyListener, it requires the following fields:

public void keyPressed(KeyEvent e) 
{

}
public void keyReleased(KeyEvent e) 
{

}
public void keyTyped(KeyEvent e) 
{

}

When i put System.out.println(e) into the keyPressed method, though, it returns this when i press the enter key:

java.awt.event.KeyEvent[KEY_PRESSED,keyCode=10,keyText=?,keyChar=?,keyLocation=KEY_LOCATION_STANDARD,rawCode=0,primaryLevelUnicode=0,scancode=0] on javax.swing.JButton[,1,1,100x100,alignmentX=0.0,alignmentY=0.5,border=com.apple.laf.AquaButtonBorder$Dynamic@13b33a0e,flags=288,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=2,bottom=0,right=2],paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=HI,defaultCapable=true]

This is obviously not a KeyEvent, so I cannot use it to call the keyPressed(KeyEvent e). What I want to be able to do is simulate the pressing of a key, specifically the enter key, in a way that would activate the keyListener and would output that text into a JTextArea.

Note: I looked at the accepted answer for How can I perfectly simulate KeyEvents?, and understood little of how it actually works, and i want code i understand. I also looked here How to simulate keyboard presses in java?, but not i could not get the robot to work; nothing happened when a key was supposed to be pressed.


Solution

  • e is the KeyEvent.

    if you want to see the e value, then you can try this

    System.out.println(e.getKeyChar());
    

    Creating KeyEvent :

    KeyEvent e = new KeyEvent(Component source, int id, long when, int modifiers, int keyCode, char keyChar, int keyLocation);
    

    Example (dunno if this is the right way, but it produce the right output):

    Button a = new Button("click");
        KeyEvent e;
        e = new KeyEvent(a, 1, 20, 1, 10, 'a');
        System.out.println(""+e.getKeyChar());
        System.out.println(""+e.getKeyCode());
    

    Here is the all type of KeyEvent parameters

    java.​awt.​event.​KeyEvent
    @Deprecated public KeyEvent(Component source, int id, long when, int modifiers, int keyCode)
    Deprecated. as of JDK1.1
    

    ===

    java.​awt.​event.​KeyEvent
    public KeyEvent(Component source, int id, long when, int modifiers, int keyCode, char keyChar)
    Constructs a KeyEvent object.
    Note that passing in an invalid id results in unspecified behavior. This method throws an IllegalArgumentException if source is null.
    Parameters:
    source - the Component that originated the event id - an integer identifying the type of event when - a long integer that specifies the time the event occurred modifiers - the modifier keys down during event (shift, ctrl, alt, meta) Either extended _DOWN_MASK or old _MASK modifiers should be used, but both models should not be mixed in one event. Use of the extended modifiers is preferred. keyCode - the integer code for an actual key, or VK_UNDEFINED (for a key-typed event) keyChar - the Unicode character generated by this event, or CHAR_UNDEFINED (for key-pressed and key-released events which do not map to a valid Unicode character) 
    Throws:
    IllegalArgumentException - if id is KEY_TYPED and keyChar is CHAR_UNDEFINED; or if id is KEY_TYPED and keyCode is not VK_UNDEFINED IllegalArgumentException - if source is null
    

    ===

    java.​awt.​event.​KeyEvent
    public KeyEvent(Component source, int id, long when, int modifiers, int keyCode, char keyChar, int keyLocation)