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Thread: how to know user pressed a key in the keyboard

  1. #1
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    Exclamation how to know user pressed a key in the keyboard

    hi all,

    how to know user pressed a key in the keyboard expect using keyListener.
    thanks a lot for your help.


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    Default Re: how to know user pressed a key in the keyboard

    Tell us your problem first

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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    im doing console programming in java, and i wanna know how to do the press any key to continue thing, so watever key is pressed then it does something, i know how to read user input but i dont think thats how to do it. Thanks

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    Default Re: how to know user pressed a key in the keyboard


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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    i just wanna detect a key press

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    Default Re: how to know user pressed a key in the keyboard

    Each key press will return a key ascii code so u have to find the maximum and minimum Ascii key value form the links i given to you then make a logic like

    if( minKeyAscii >= KEY_TYPED && KEY_TYPED <= maximum )

    I think this will fix your problem. Try your level best, good luck.

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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    Maybe use the Scanner class.

    // Json

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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    Quote Originally Posted by Json View Post
    Maybe use the Scanner class.

    // Json
    Something like this?

    import java.util.Scanner;
     
    public class Cilang {
     
        /**
         * JavaProgrammingForums.com
         */
        public static void main(String[] args) {
     
            System.out.println("Java Programming Forums");
            System.out.println("Continue? (y/n)");
            Scanner sc = new Scanner(System.in);
     
            if(sc.next().equals("y")){
                DoSomething();
            }else{
                System.out.println("Bye!");
            }
     
     
        }
     
        public static void DoSomething(){        
            System.out.println("Hello World!");        
        }    
    }
    Only problem with using the Scanner class like this is you have to press Enter for it to register.
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    I dont think its possible to just detect one keypress from the System.in inputstream unless the keypress is the return/new line key.

    The problem is that the OS does not send the data to the inputstream until the return key is pressed

    // Json

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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    *cough* JNI.
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

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    cilang (September 10th, 2009)

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    Default Re: how to know user pressed a key in the keyboard

    Quote Originally Posted by Freaky Chris View Post
    *cough* JNI.
    What a surprise!!

    Java Native Interface - Wikipedia, the free encyclopedia
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    Default Re: how to know user pressed a key in the keyboard

    Its not my fault there is a large volume of JNI questions flooding into the forum!
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  20. #13
    Super Moderator Json's Avatar
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    Default Re: how to know user pressed a key in the keyboard

    haha

    *cough* didnt expect that from you *cough*

    Maybe we need to start putting together some nice JNI common stuff

    // Json

  21. #14
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    Default Re: how to know user pressed a key in the keyboard

    Did you just use nice and JNI in the same sentence!?
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

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    Super Moderator Json's Avatar
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    Default Re: how to know user pressed a key in the keyboard

    Possibly :/

    // Json

  23. #16
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    Default Re: how to know user pressed a key in the keyboard

    excuse me ., its not related on this post .. but i want to ask something.

    i modified javaPF's reply(code) about this thread..
    public class Cilang {
     
        /**
         * JavaProgrammingForums.com
         */
        Scanner sca = new Scanner(System.in);
        public static void main(String[] args) {
     
            System.out.println("Java Programming Forums");
            System.out.println("Continue? (y/n)");
            Scanner sc = new Scanner(System.in);
     
            String input = sc.next();
     
            if (input == "y"){
                DoSomething();
            }else{
                System.out.println("Bye!");
            }
     
     
        }
     
        public static void DoSomething(){
            System.out.println("Hello World!");
        }
    }

    i just used some boolean expression THAT IF input has a value which is 'y' then it will do the statement in the if block,

    but why isnt running?

    im just trying to apply some logic behind that... (i.e. if i entered 'y' then pop it up)

    but i ended up in error
    it only prints the ELSE statement "bye"
    Last edited by chronoz13; September 11th, 2009 at 04:42 AM.

  24. #17
    Super Moderator Json's Avatar
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    Default Re: how to know user pressed a key in the keyboard

    Because this if statement.

    if (input == "y") {

    Should look like this to work.

    if ("y".equalsIgnoreCase(input)) {

    There is another thread somewhere discussing why you shouldnt use the == when comparing strings.

    // Json

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