GWT numberformat weird behaviour - gwt

Question

I have a GWT project for which the locale is set to fr. I have a custom text field that uses a number format to validate and format the numerical inputs.
The formatting works fine but not the input validation. Here is a snapshot of the method that validates that the new value is a valid percentage (this is called onValueChanged):
private void validateNumber(String newVal){
logger.debug("value changed, newVal="+newVal+", current="+current);
// Attempt to parse value
double val=0;
try{
val=Double.parseDouble(newVal);
}catch(NumberFormatException e){
logger.warn("parsing failed",e);
try{
val=getFormatter().parse(newVal);
}catch(NumberFormatException ex){
logger.warn("parsing with nb format failed",ex);
// on failure: restore previous value
setValue(current,false);
return;
}
}
//some check on min and max value here
}
For example if the starting value is set by the program to "0.2" it will show up as 20,00 % hence using the correct decimal separator.
Now:
if I input 0,1 I get a numberformat exception.
if I input 0.1 it show as 10,00 %
if I 10% (without the space before the '%'), I get a numberformat exception
Do you know how I can modify the method to have 0,1 and 10% identified as valid inputs?

Answer 1

As Colin mentioned, you definitely want to parse and format using a GWT Number Format object, not Double, so the parsing and formatting are properly locale specific.
Below is some code snippets I could find to parse, validate and format a percent number.
Note however the edit process has the % unit hard-coded outside of the text box value, hence no conversion between 20,45% and 0.2045 in the edit process, 20,45 is entered directly and visualized as such. I vaguely recall struggling with such conversion during the edit process but forgot the details as it was a while back. So if it is a critical part of your question and requirements then I am afraid the examples below may be of limited value. Anyway, here they are!
Notations:
TextBox txt = new TextBox();
NumberFormat _formatFloat = NumberFormat.getFormat("#,##0.00");
NumberFormat _formatPercent = NumberFormat.getFormat("##0.00%");
Parsing text entry like "20,45" as 20.45 (not "20,45%" as 0.2045):
txt.setText("20,45"); // French locale format example, % symbol hard-coded outside of text box.
try {
float amount = (float) _formatFloat.parse(txt.getText());
} catch (NumberFormatException e) ...
Parsing & Validating text entry like "20,45":
private class PercentEntryValueChangeHandler implements ValueChangeHandler<String>
{
#Override
public void onValueChange(ValueChangeEvent<String> event)
{
validatePercent((TextBox) event.getSource());
}
};
private void validatePercent(final TextBox percentTextBox)
{
try
{
if (!percentTextBox.getText().isEmpty())
{
final float val = (float) _formatFloat.parse(percentTextBox.getText());
if (isValid(val))
percentTextBox.setText(_formatFloat.format(val));
else
{
percentTextBox.setFocus(true);
percentTextBox.setText("");
Window.alert("Please give me a valid value!");
}
}
}
catch (NumberFormatException e)
{
percentTextBox.setFocus(true);
percentTextBox.setText("");
Window.alert("Error: entry is not a valid number!");
}
}
private boolean isValid(float val) { return 12.5 < val && val < 95.5; }
txt.addValueChangeHandler(new PercentEntryValueChangeHandler());
Formatting 20.45 as "20,45":
float val = 20.45;
txt.setText(_formatFloat.format(val));
Formatting 0.2045 as "20,45%" (read only process, the text box is not editable, the % is set inside the text box):
float val = 0.2045;
txt.setText(_formatPercent.format((double)(val))); // * 100 embedded inside format.
It is not fancy and probably far from perfect but it works!
Any feedback on how to improve upon this implementation is more than welcome and appreciated!
I hope it helps anyway.

Answer 2

I managed to make it work by changing the code to the following:
private void validateNumber(String newVal){
double val=0;
try{
val=getFormatter().parse(newVal);
}catch(NumberFormatException e){
boolean ok=false;
try{
val=NumberFormat.getDecimalFormat().parse(newVal);
ok=true;
}catch(NumberFormatException e1){}
if(!ok){
try{
val=Double.parseDouble(newVal);
}catch(NumberFormatException ex){
setValue(current,false);
// inform user
Window.alert(Proto2.errors.myTextField_NAN(newVal));
return;
}
}
}