Re: How to create your own numeric components ?

["Luther Ananda Miller" <luther.miller@xxxxxxxxxx>]

Add a document listener to the document attached to the JTextField. Then you
cn listen for the three events which causes chages to the text field value
regardless of how they are entered (keypress does not cover them all). Just
check the end result of the event for validity.

luther

----- Original Message -----
From: Geert Van Landeghem <gvl@reynderseti.be>
To: Java400-L (E-mail) <java400-l@midrange.com>
Sent: Wednesday, 19 January 2000 16:08
Subject: How to create your own numeric components ?


> Hi All,
>
> I'm trying to create my own numeric textfields: I've created a subclass of
> JTextField and I'm using the KeyPressed
> method to obtain control over digits and separators entered.
>
> Is there a way to obtain the position of the cursor in the field when
> generating each KeyEvent?
>
> when using the following code:
>    JRNumField jrn_myfield=new JRNumField(6,2, '.');
>    // creates a numeric textfield with 6 positions and 2 decimals and '.'
as
> separator
> following valid values can be entered:
>   1234.56
>   12.56
>   1234
>   ...
> but also:
>   12.234
>   12221.1
> To resolve this problem I need a way to obtain the position of the cursor
> (before or after the separator)
> Has anybody an idea how to do this or are there some 'home-made'
components
> already available with the
> the same functionality?
>
> the code I'm using in keyPressed follows:
>
> /**
>  * This method was created in VisualAge.
>  * @param ke java.awt.event.KeyEvent
>  */
> public void keyTyped(KeyEvent ke) {
>   // getLength() returns total number of digits
>   // getDecimals() returns the digits after the separator
>   // getNotation returns the type of separator (comma or period)
>   char typedChar=ke.getKeyChar();
>   int length= getPositions();
>
>   // calculate the position of the separator
>   int pos=getText().indexOf(getNotation());
>   // set separator to true if separator has allready been entered
>   boolean separator=pos > -1;
>
>   System.out.println("Keyevent=" + ke);
>
>   // calculate the maximum total length in characters
>   // if decimals specified add 1 to total length(separator)
>   if (getDecimals() > 0) {
> length++;
>   }
>   // logging
>   System.out.println("Event = " + ke + getText());
>
>   // if length of field is equal to maximum length-1
>   // consume the KeyEvent: throw it away!
>   if (getText().length() > length-1){
>   if (getSelectedText().compareTo(getText())==0) {
>   setText("");
>   return;
>   }
>      System.out.println("String to long");
>   ke.consume();
>   return;
>   }
>
>
>   // test the character being entered
>   // is character a digit?
>   else if (Character.isDigit(typedChar))

>   System.out.println("It is a digit!");
>   // if decimals specified and seperator has been found
>   if (getDecimals() > 0 && separator) {
>       int numBefore=pos;
>   int numAfter=getText().length()- (pos+1);
>   // is number of digits before or after seperator reached?
>   // logging
>   System.out.println("Length= " + getText().length() + "
> Position= " + pos + " before="+ numBefore + " numAfter=" + numAfter + "
> decimals=" +getDecimals());
>   if  (numBefore <= getPositions()-getDecimals() && numAfter
> <= getDecimals()) {
>      return;
>      // !! not correct !!
>      // !! you need to know the position where the character
> has been entered...
>      // !! (where the KeyEvent is being generated)
>   }
>   else {
>   ke.consume();
>   return;
>   }
>   }
>   else if (getDecimals() > 0 && !separator) {
>   // if decimals specified and no seperator has been found
>
>       if (getText().length() > getPositions()-getDecimals()-1) {
>   ke.consume();
>   return;
>   }
>   return;
>   }
>   }
>
>   // is character equal to separator?
>   else if (ke.getKeyChar()== getNotation() && getDecimals() > 0){
>   System.out.println("It is a seperator!");
>   // if seperator has allready been used?
>   if (separator) {
>   System.out.println("Separator has already been used");
>   ke.consume();
>   }
>   else {
>   System.out.println("This is the separator!");
>     return;
>   }
>   }
>
>   // no valid character entered
>   // throw away event
>   else {
>   System.out.println("No seperator and no digit!");
>   ke.consume();
>   return;
>   }
> }
>
>
> --------------------------------------------------------------------------
--
> ----------
> Geert Van Landeghem
> Reynders Etiketten
> gvl@reynderseti.be (Office)
> hydra@vt4.net (Home)
> 03/460.12.56 (Office)
> 0477/759.533 (GSM)
>
> <<never play leapfrog with a unicorn>>
> --------------------------------------------------------------------------
--
> ----------
>
>
>
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