Validation in swt text - text

Question

I would like to validate numbers input in text box.
I want the user to input only integer, decimal in the box between a maximum and minimum values.
How can I make sure of this?
Thank you.

Answer 1

Use a VerifyListener as this will handle paste, backspace, replace.....
E.g.
text.addVerifyListener(new VerifyListener() {
#Override
public void verifyText(VerifyEvent e) {
final String oldS = text.getText();
final String newS = oldS.substring(0, e.start) + e.text + oldS.substring(e.end);
try {
BigDecimal bd = new BigDecimal(newS);
// value is decimal
// Test value range
} catch (final NumberFormatException numberFormatException) {
// value is not decimal
e.doit = false;
}
}
});

Answer 2

You can register a ModifyListener with the text control and use it to validate the number.
txt.addModifyListener(new ModifyListener() {
#Override
public void modifyText(ModifyEvent event) {
String txt = ((Text) event.getSource()).getText();
try {
int num = Integer.parseInt(txt);
// Checks on num
} catch (NumberFormatException e) {
// Show error
}
}
});
You could also use addVerifyListener to prevent certain characters being entered. In the event passed into that method there is a "doit" field. If you set that to false it prevents the current edit.

Answer 3

Integer validation in SWT
text = new Text(this, SWT.BORDER);
text.setLayoutData(gridData);
s=text.getText();
this.setLayout(new GridLayout());
text.addListener(SWT.Verify, new Listener() {
public void handleEvent(Event e) {
String string = e.text;
char[] chars = new char[string.length()];
string.getChars(0, chars.length, chars, 0);
for (int i = 0; i < chars.length; i++) {
if (!('0' <= chars[i] && chars[i] <= '9')) {
e.doit = false;
return;
}
}
}
});

Answer 4

If you only want to allow Integer values you could use a Spinner instead of a text field.
For the validation of Double values you have to consider that characters like E may be included in Doubles and that partial input like "4e-" should be valid while typing. Such partial expressions will give a NumberFormatException for Double.parseDouble(partialExpression)
Also see my answer at following related question:
How to set a Mask to a SWT Text to only allow Decimals

Answer 5

1.create a utill class implement verify listener
2.override verifytext method
3.implement your logic
4.create a object of utill class where you want to use verify listener (on text)
5.text.addverifylistener(utillclassobject)
Example :-
1. utill class:-
public class UtillVerifyListener implements VerifyListener {
#Override
public void verifyText(VerifyEvent e) {
// Get the source widget
Text source = (Text) e.getSource();
// Get the text
final String oldS = source.getText();
final String newS = oldS.substring(0, e.start) + e.text + oldS.substring(e.end);
try {
BigDecimal bd = new BigDecimal(newS);
// value is decimal
// Test value range
} catch (final NumberFormatException numberFormatException) {
// value is not decimal
e.doit = false;
}
}
2.use of verifylistener in other class
public class TestVerifyListenerOne {
public void createContents(Composite parent){
UtillVerifyListener listener=new UtillVerifyListener();
textOne = new Text(composite, SWT.BORDER);
textOne .setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 1, 1));
textOne .addVerifyListener(listener)
textTwo = new Text(composite, SWT.BORDER);
textTwo .setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 1, 1));
textTwo .addVerifyListener(listener);
}
}

Answer 6

text.addVerifyListener(new VerifyListener() {
#Override
public void verifyText(VerifyEvent e) {
Text text = (Text) e.getSource();
final String oldS = text.getText();
String newS = oldS.substring(0, e.start) + e.text + oldS.substring(e.end);
boolean isValid = true;
try {
if(! "".equals(newS)){
Float.parseFloat(newS);
}
} catch (NumberFormatException ex) {
isValid = false;
}
e.doit = isValid;
}
});