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Need help dealing with keyboard listener in java

  1. Nov 1, 2011 #1
    I have a program which uses a keyboard listener and moves a character in the program when the user places a key. However when the user lets go of the key the character keeps going a few more steps. I think what is happening is that I use a while loop and make it wait a few seconds in order to draw an animation for the character and while this is happening the keyboard is still taking in data and queuing it up then finishing everything in the queue after the player lets go of the button, I'm not completely sure if thats the problem, just what i think.

    Here is the code im using:
    Code (Text):
     public void movePlayer(int deltaX, int deltaY) throws IOException
      {
        inMovement=true;
        location[0]+=deltaX;
        location[1]+=deltaY;
        if(phaseNum==0)
        {
          phaseNum=1;
        }
        else if(phaseNum==1)
        {
          phaseNum=0;
        }
          playerPhase="player"+phaseNum+".gif";
          File input = new File(playerPhase);
          secondImage = ImageIO.read(input);
          this.paintImmediately(0, 0, 500, 500);
        long start=System.nanoTime();
        //sets the variable start to the current time then waits 200000000 nanoseconds or 0.2 seconds
        while(System.nanoTime()-start<105000000)
        {
         
        }
         if(phaseNum==0)
        {
          phaseNum=1;
        }
        else if(phaseNum==1)
        {
          phaseNum=0;
        }
          playerPhase="player"+phaseNum+".gif";
          input = new File(playerPhase);
          secondImage = ImageIO.read(input);
          location[0]+=deltaX;
          location[1]+=deltaY;
          this.paintImmediately(0, 0, 500, 500);
    }
         
    the method gets called in the method keyPressed(KeyEvent e)
    So I'm just wondering how to stop the character from moving right when the player lets go of the key instead of having the character continue to move for a few more steps. and the longer the player holds down a key the more steps the character takes after the player lets go.
     
  2. jcsd
  3. Nov 1, 2011 #2

    Mark44

    Staff: Mentor

    You might need another handler, one that is called when a key is released, or else modify your keyPressed method. This link might be helpful -http://download.oracle.com/javase/1.4.2/docs/api/java/awt/event/KeyEvent.html. [Broken]
     
    Last edited by a moderator: May 5, 2017
  4. Nov 1, 2011 #3
    I've tried a few things, and no matter what i do in a key released method it still has the same problem cause the key presses are still queued up. I'm fairly certain that it is queuing up the key presses while the program is waiting for the while method and then executes the method using those keys afterward and if i have anything in the keyReleased it doesn't matter because it doesn't go through that until after it's gone through all the actions queued up
     
  5. Nov 1, 2011 #4
    Ok, so i finally got it working by putting an if loop around the entire method which was just:

    if(System.currentTimeMillis()-e.getWhen()<2)

    thanks a lot for the help, looked at the API on the link you posted.
     
  6. Nov 1, 2011 #5

    Mark44

    Staff: Mentor

    Don't call it an if loop or no one will understand what you're talking about. An if structure is a decision control structure, that decides whether one path or another will execute, based on the value of an expression.

    A loop executes a certain group of statements repeatedly.
     
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