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/** From 'Programming in Qt', page 180 */
import org.kde.qt.*;
/**
* A class that validates ISBN numbers. See the text for the
* specification.
*/
public class ISBNValidator extends QValidator
{
public ISBNValidator()
{
super(null,null);
}
/**
* This method is called after every input. Since we can check every
* character as soon as it is entered, we only need to check one
* character at a time for validity. To determine whether
* the whole string is acceptable, we must look at the whole
* string
* Note that input can also be deleted. This makes it useless
* to save state (like the number of entered digits) between
* invocations of validate(), because we would have to keep an extra
* copy of the last string.
*/
public int validate(StringBuffer text, int[] position)
{
int pos = position[0] - 1;
if( text.length() == 0 )
return Valid;
/* Protect against spurious calls to validate() */
if (pos > text.length() )
return Valid;
/* Anything but decimal digits and dashes is invalid. We only need
* to check the character at the cursor positions. This speeds
* things up massively.
*/
if( !Character.isDigit(text.charAt(pos)) && ( text.charAt(pos) != '-' ) )
{
System.out.println( "Typed character is neither digit nor dash" );
return Invalid;
}
/* Dashes are only valid at position 1 (the second position),
* position 8 (if there was no dash at position 1), or position 9 (if
* there was a dash at position 1).
*/
if( text.charAt(pos) == '-' )
{
if( pos != 1 && pos != 8 && pos != 9 )
{
System.out.println( "Dash at wrong position" );
return Invalid;
}
if( ( pos == 8 && text.charAt(1) == '-' ) ||
( pos == 9 && text.charAt(1) != '-' ) )
{
System.out.println( "Dash at wrong position" );
return Invalid;
}
}
/* If the characters entered so far are valid, but the string
* contains less than ten digits, it could be made acceptable, but
* is not yet.
*/
int numdigits = text.length();
if( text.length() > 1 && text.charAt(1) == '-' ) numdigits--;
if( text.length() > 8 && text.charAt(8) == '-' ) numdigits--;
if( text.length() > 9 && text.charAt(9) == '-' ) numdigits--;
if( numdigits < 10 )
{
System.out.println( "Less than ten digits; input valid but not yet acceptable" );
return Valid;
}
if( numdigits > 10 )
{
System.out.println( "More than ten digits; input invalid" );
return Invalid;
}
if( text.charAt(1) != '-' || text.charAt(9) != '-' )
{
System.out.println( "Ten digits, but dashes not in the right places. Could be fixed up" );
return Valid;
}
System.out.println( "Input acceptable" );
return Acceptable;
}
/**
* This method is called when the user has pressed return, but
* validate() has judged the string valid but not acceptable. Note
* that fixup() is not required to return an acceptable string. It is
* guaranteed that the caller will validate() the string once again
* after the call to fixup().
*/
public void fixup(StringBuffer text)
{
/* We can fix the input only if the dashes are missing,
* since we cannot implement the missing digits. (We could at least
* compute the last one with the checksum algorithm, but won't do so
* here.)
*/
/* If at least one digit has been entered but there is no dash at
* position 1, insert one.
*/
if( text.length() > 1 && text.charAt(1) != '-' )
text.insert( 1, "-" );
/* If at least nine digits have been entered but there is no dash
* at position 10 (because of the last two lines, we can safely
* assume that the first dash is already in place), insert one.
*/
if( text.length() > 10 /* nine digits plus dash */ && text.charAt(10) != '-' )
text.insert( 10, "-" );
}
public static void main(String[] args)
{
class ReturnReceiver extends QObject {
public void slotReturnPressed()
{
System.out.println( "return pressed - input accepted" );
}
}
QApplication myapp = new QApplication( args );
// create a line edit
QLineEdit myedit = new QLineEdit((QWidget) null);
myedit.resize( 100, 30 );
// create and assign a validator for the line edit
ISBNValidator myvalidator = new ISBNValidator();
myedit.setValidator(myvalidator);
// set up a receiver for the returnPressed() signal
ReturnReceiver receiver = new ReturnReceiver();
QObject.connect( myedit, SIGNAL( "returnPressed()" ),
receiver, SLOT( "slotReturnPressed()" ) );
myapp.setMainWidget( myedit );
myedit.show();
myapp.exec();
return;
}
static {
qtjava.initialize();
}
}
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