Processing 1.0 - Processing Discourse - on screen keyboard for touch screen

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Index › Programming Questions & Help › Syntax Questions › on screen keyboard for touch screen

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on screen keyboard for touch screen (Read 931 times)

Terry_Bell

on screen keyboard for touch screen
Feb 20^th, 2010, 10:49am

I am working on building an on screen keyboard to use with a touch interface.

I was wondering if anyone had any suggestions?

Currently I am writing a button class and instancing 26 objects of that class. Each mousePress (simulating the users touch) is checking if it sits inside any of those objects.

Does any one have a better method for doing this? Or a quick way I can create all my button instances? I am currently doing something like:

q = new Button('q', xpos, ypos);
w = new Button('w', xpos, ypos);

etc.

Haven't quite figured out the best way to generate the xpos/ypos info yet.

Thanks,
TB

PhiLho

Re: on screen keyboard for touch screen
Reply #1 - Feb 20^th, 2010, 12:31pm

Code:

String[] chars = { "a", "b", ... "z", ",", ".", "!" ... };
Button[] touches = new Button[chars.length];
for (int i = 0; i < chars; i++) {
  // If pos can be found algorithmically
  int xpos = ...;
  int ypos = ...;
  touches[i] = new Button(chars[i], xpos, ypos);
}

Terry_Bell

Re: on screen keyboard for touch screen
Reply #2 - Feb 21^st, 2010, 7:20pm

Thanks!

I have implemented your code and it works great.

I am now working on a method in the button class that returns the corresponding key of that button.

Code:


char keyCheck(int Xmouse, int Ymouse){
    //check if click was inside key
    if(Xmouse > x && Xmouse < x + keySize 
		&& Ymouse > y && Ymouse < y + keySize){
     return keyVal;
    }
    return null;
  }

Basically - i only want the key value returned if the click falls within the button area, otherwise I don't want anything returned. The above code gives the error:

'cannot convert from null to char'

Any advice?

Thanks,
TB

Cedric YaBB Moderator Offline Posts: 1838	Re: on screen keyboard for touch screen Reply #3 - Feb 21^st, 2010, 7:47pm hey terry, just curious. what are you working on ?
	twitter.com/CedricKiefer

PhiLho

Re: on screen keyboard for touch screen
Reply #4 - Feb 21^st, 2010, 10:11pm

char is a primitive type, actually represented by the Unicode (or Ascii, if you prefer) value of the character.
So you can't return null in place of a char.
If you used Strings as I did, you could return null...
Or return Character type, the class wrapper of the char type.
Or return a special char value, eg. \uFFFF (-1) which is an invalid Unicode value.

Terry_Bell

Re: on screen keyboard for touch screen
Reply #5 - Feb 21^st, 2010, 11:40pm

Hrmm....i think I am getting a little in over my head.

I converted the char to a String using Character.toString - now I cant figure out why this string prints fine from within the button class, but always returns a string with content "null", or infact any string i place in that else{return ... } section.

Code:

char[] chars = new char[26];
Button[] touches = new Button[chars.length];

int charVal = 97;
int xpos = 10;
int ypos = 10;
String lastPress;

void setup(){
  size(930,200);
  for (int i = 0; i < chars.length; i++) {
    chars[i] = char(charVal);
    charVal++;
    touches[i] = new Button(chars[i], xpos, ypos);
    xpos += 35;
  }
}

void draw(){
  for (int i = 0; i < touches.length; i++){
    touches[i].display();
  }
}

void mouseReleased(){
  for (int i = 0; i < touches.length; i++){
    lastPress = touches[i].keyCheck(mouseX, mouseY);
  }
 println(lastPress); //prints "null"
}

Code:

class Button {

  String charString;
  int x;
  int y;
  int keySize = 30;

  Button(char keyVal, int x, int y){
    charString = Character.toString(char(keyVal));
    this.x = x;
    this.y = y;
  }

  void display(){
    rect(x,y,keySize,keySize); 
  }

  String keyCheck(int Xmouse, int Ymouse){
    if(Xmouse > x && Xmouse < x + keySize 
        && Ymouse > y && Ymouse < y + keySize){
      println(charString); //prints relevant char
      return charString;
    }  else {
      return null;
    }
  }
}

Terry_Bell

Re: on screen keyboard for touch screen
Reply #6 - Feb 21^st, 2010, 11:47pm

Cedric wrote on Feb 21^st, 2010, 7:47pm:

hey terry, just curious. what are you working on

Working on an installation that allows a user to generate their own unique piece of art (in processing). I then want the user to have the option of emailing a saved frame to themselves. I have access to a touch screen and thought it'd be a tidier way to give them this option than a wired keyboard. Will also give me more control over what they can enter.

And I've just started learning OOP and thought it'd be a good project to try and capitalize on that.

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: on screen keyboard for touch screen Reply #7 - Feb 22^nd, 2010, 1:33am The idea was to have chars as a String array too, so you don't have char type anymore. It is more annoying the hand-write the full alphabet, but for e-mail, you have to add some additional chars anyway (@ . - _ as a strict minimum).

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