Programming Forums > Application Development > Java

asddsa · Jun 17th, 2005, 8:35 AM

how do i do that?

HeX · Jun 17th, 2005, 8:39 AM

how do you do what?

asddsa · Jun 17th, 2005, 8:41 AM

"press any key to continue",
i want to continue my code just after the user presses a key...

HeX · Jun 17th, 2005, 8:56 AM

you can do that with a KeyListener
look in google

asddsa · Jun 17th, 2005, 5:15 PM

can you help me with this one...
i found KeyListener just in a new window (JFrame), and i want to use it in the "dos" window...

EdSalamander · Jun 17th, 2005, 6:17 PM

It's a bit of a hack, but you could create a "ghost" Component that has a KeyListener registered to it. You don't need to actually show this component or even use it for anything else, just have it listen in for KeyEvents.

These might help:
Sun's tutorial on KeyListeners
The Java API (look up KeyListener and Component)

VigilanteP@comcast.net · Jun 17th, 2005, 9:48 PM

Nevermind --- my suggestion didnt work.

ZenMasterJG · Jun 18th, 2005, 5:37 AM

define a function like this (blatantly stolen from savitch)

(Toggle Plain Text)

 /**
     Reads a line of text and returns that line as a String
     value. The end of a line must be indicated either by a
     new-line character '\n' or by a carriage return '\r'
     followed by a new-line character '\n'. (Almost all systems
     do this automatically. So you need not worry about this
     detail.) Neither the '\n', nor the '\r' if present, are
     part of the string returned. This will read the rest of a
     line if the line is already partially read.
    */
    public static String readLine( )
    {
        char nextChar;
        String result = "";
        boolean done = false;

        while (!done)
        {
            nextChar = readChar( );
            if (nextChar == '\n')
               done = true;
            else if (nextChar == '\r')
            {
                //Do nothing.
                //Next loop iteration will detect '\n'.
            }
            else
               result = result + nextChar;
        }

        return result;
    }

then do somthing like:

(Toggle Plain Text)

System.out.println("Press any key to continue.");
readLine();

that readline function will work for most any string based input.
good luck!

VigilanteP@comcast.net · Jun 18th, 2005, 12:51 PM

"Press any key to continue" ..

Won't your loop only terminate if the user enters a newline character (enter)?

EdSalamander · Jun 18th, 2005, 4:57 PM

Correct, this code only works when "enter" is pressed. Actually, it doesn't work at all beause readChar() isn't actually defined, but we'll overlook that for a minute. The real problem with trying to read from an input stream (esp. System.in) is that control isn't returned to the main thread until the return key is pressed anyway. You can hit all the keys and enter all the characters you want, but none of them will actually be read until you hit return and give contol back to the program.

To be fair, the method I suggested earlier about using a "ghost" Component won't work either. I forgot that Components need to have focus before they can listen in for KeyEvents, and they can't have focus unless they're visible.

In short, I don't think what you're trying to do is possible; not in Java anyway. I say just go with "Press Enter to Continue" and be done with it.

Jun 17th, 2005, 8:35 AM	#1
asddsa Newbie Join Date: Jun 2005 Posts: 4 Rep Power: 0	press any key to continue how do i do that?

Jun 17th, 2005, 8:39 AM	#2
HeX Programmer Join Date: May 2005 Location: Kosova Posts: 94 Rep Power: 4	how do you do what? __________________ (Toggle Plain Text) countdown++; countdown++;

Jun 17th, 2005, 8:56 AM	#4
HeX Programmer Join Date: May 2005 Location: Kosova Posts: 94 Rep Power: 4	you can do that with a KeyListener look in google __________________ (Toggle Plain Text) countdown++; countdown++;

Jun 17th, 2005, 6:17 PM	#6
EdSalamander Programmer Join Date: Dec 2004 Location: Tucson, AZ, USA Posts: 80 Rep Power: 4	It's a bit of a hack, but you could create a "ghost" Component that has a KeyListener registered to it. You don't need to actually show this component or even use it for anything else, just have it listen in for KeyEvents. These might help: Sun's tutorial on KeyListeners The Java API (look up KeyListener and Component) __________________ I can pick my friends. And I can pick my nose. So, why can't I pick my friend's nose?

Jun 17th, 2005, 9:48 PM	#7
VigilanteP@comcast.net Newbie Join Date: Jun 2005 Posts: 8 Rep Power: 0	Nevermind --- my suggestion didnt work. Last edited by VigilanteP@comcast.net; Jun 17th, 2005 at 9:53 PM.

Jun 17th, 2005, 8:41 AM	#3
asddsa Newbie Join Date: Jun 2005 Posts: 4 Rep Power: 0	"press any key to continue", i want to continue my code just after the user presses a key...

Jun 17th, 2005, 5:15 PM	#5
asddsa Newbie Join Date: Jun 2005 Posts: 4 Rep Power: 0	can you help me with this one... i found KeyListener just in a new window (JFrame), and i want to use it in the "dos" window...

Jun 18th, 2005, 5:37 AM	#8
ZenMasterJG Hobbyist Programmer Join Date: Nov 2004 Location: Boston, MA Posts: 148 Rep Power: 5	define a function like this (blatantly stolen from savitch) (Toggle Plain Text) /** Reads a line of text and returns that line as a String value. The end of a line must be indicated either by a new-line character '\n' or by a carriage return '\r' followed by a new-line character '\n'. (Almost all systems do this automatically. So you need not worry about this detail.) Neither the '\n', nor the '\r' if present, are part of the string returned. This will read the rest of a line if the line is already partially read. / public static String readLine( ) { char nextChar; String result = ""; boolean done = false; while (!done) { nextChar = readChar( ); if (nextChar == '\n') done = true; else if (nextChar == '\r') { //Do nothing. //Next loop iteration will detect '\n'. } else result = result + nextChar; } return result; } /* Reads a line of text and returns that line as a String value. The end of a line must be indicated either by a new-line character '\n' or by a carriage return '\r' followed by a new-line character '\n'. (Almost all systems do this automatically. So you need not worry about this detail.) Neither the '\n', nor the '\r' if present, are part of the string returned. This will read the rest of a line if the line is already partially read. */ public static String readLine( ) { char nextChar; String result = ""; boolean done = false; while (!done) { nextChar = readChar( ); if (nextChar == '\n') done = true; else if (nextChar == '\r') { //Do nothing. //Next loop iteration will detect '\n'. } else result = result + nextChar; } return result; } then do somthing like: (Toggle Plain Text) System.out.println("Press any key to continue."); readLine(); System.out.println("Press any key to continue."); readLine(); that readline function will work for most any string based input. good luck!

Jun 18th, 2005, 12:51 PM	#9
VigilanteP@comcast.net Newbie Join Date: Jun 2005 Posts: 8 Rep Power: 0	"Press any key to continue" .. Won't your loop only terminate if the user enters a newline character (enter)?

Jun 18th, 2005, 4:57 PM	#10
EdSalamander Programmer Join Date: Dec 2004 Location: Tucson, AZ, USA Posts: 80 Rep Power: 4	Correct, this code only works when "enter" is pressed. Actually, it doesn't work at all beause readChar() isn't actually defined, but we'll overlook that for a minute. The real problem with trying to read from an input stream (esp. System.in) is that control isn't returned to the main thread until the return key is pressed anyway. You can hit all the keys and enter all the characters you want, but none of them will actually be read until you hit return and give contol back to the program. To be fair, the method I suggested earlier about using a "ghost" Component won't work either. I forgot that Components need to have focus before they can listen in for KeyEvents, and they can't have focus unless they're visible. In short, I don't think what you're trying to do is possible; not in Java anyway. I say just go with "Press Enter to Continue" and be done with it. __________________ I can pick my friends. And I can pick my nose. So, why can't I pick my friend's nose? Last edited by EdSalamander; Jun 18th, 2005 at 5:02 PM.

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