Regex for javafx spinner control - regex

Question

SpinnerValueFactory svf = new SpinnerValueFactory.DoubleSpinnerValueFactory(-500,500,1,0.5);
spiKolicina.setValueFactory(svf);
spiKolicina.setEditable(true);
UnaryOperator<TextFormatter.Change> filter = new UnaryOperator<TextFormatter.Change>() {
#Override
public TextFormatter.Change apply(TextFormatter.Change t) {
if (t.isReplaced())
if(t.getText().matches("[^0-9]"))
t.setText(t.getControlText().substring(t.getRangeStart(), t.getRangeEnd()));
if (t.isAdded()) {
if (t.getControlText().contains(".")) {
if (t.getText().matches("[^0-9]")) {
t.setText("");
}
}
else if (t.getText().matches("[^0-9.]")) {
t.setText("");
}
}
return t;
}
};
spiKolicina.getEditor().setTextFormatter(new TextFormatter<>(filter));
How to alter regex expression to allow me to enter negative double number in spinner textfield?
Also when the spinner textfield is empty and you press the up or down btn it gives nullPointException, i would like it to go to some default value

Answer 1

I usually find it easier to check the resulting text from a change; return the change "as-is" if it is ok, and return null otherwise. Here you want the resulting text to be an optional negative sign, zero or more digits, an options decimal separator, and zero or more digits. (Note this allows any valid floating point number, or an empty string, or a negative sign or digital separator on its own.)
So for the filter:
UnaryOperator<TextFormatter.Change> filter = new UnaryOperator<TextFormatter.Change>() {
#Override
public TextFormatter.Change apply(TextFormatter.Change t) {
String newText = t.getControlNewText() ;
if (newText.matches("-?[0-9]*\\.?[0-9]*")) {
return t ;
}
return null ;
}
};
You can also define a converter, which you can use with both the spinner itself and the text field which is the editor for the spinner. This just needs to parse the string as a double, but should handle the special cases of -, ., and -.. So:
StringConverter<Double> converter = new StringConverter<Double>() {
#Override
public String toString(Double object) {
return object.toString() ;
}
#Override
public Double fromString(String string) {
if (string.isEmpty() || ".".equals(string) || "-".equals(string) || "-.".equals(string)) {
return 0.0 ;
} else {
return new Double(string);
}
}
};
then do
svf.setConverter(converter);
spinner.getEditor().setTextFormatter(new TextFormatter<>(converter, 0.0, filter));
This converter will properly handle interpreting empty strings, etc, as 0.0, and so will avoid the exception when you try to increment or decrement when the editor is in that state.
SSCCE:
import java.util.function.UnaryOperator;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Spinner;
import javafx.scene.control.SpinnerValueFactory;
import javafx.scene.control.TextFormatter;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.StringConverter;
public class SpinnerTest extends Application {
#Override
public void start(Stage primaryStage) {
SpinnerValueFactory<Double> svf = new SpinnerValueFactory.DoubleSpinnerValueFactory(-500,500,1,0.5);
Spinner<Double> spinner = new Spinner<>();
spinner.setValueFactory(svf);
spinner.setEditable(true);
UnaryOperator<TextFormatter.Change> filter = new UnaryOperator<TextFormatter.Change>() {
#Override
public TextFormatter.Change apply(TextFormatter.Change t) {
String newText = t.getControlNewText() ;
if (newText.matches("-?[0-9]*\\.?[0-9]*")) {
return t ;
}
return null ;
}
};
StringConverter<Double> converter = new StringConverter<Double>() {
#Override
public String toString(Double object) {
return object.toString() ;
}
#Override
public Double fromString(String string) {
if (string.isEmpty() || ".".equals(string) || "-".equals(string) || "-.".equals(string)) {
return 0.0 ;
} else {
return new Double(string);
}
}
};
svf.setConverter(converter);
spinner.getEditor().setTextFormatter(new TextFormatter<>(converter, 0.0, filter));
StackPane root = new StackPane(spinner);
primaryStage.setScene(new Scene(root, 180, 80));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}