The converter is different to the filter: the converter specifies how to convert the text to a value, and the filter filters changes the user may make. It sounds like here you want both, but you want the filter to more accurately filter the changes that are allowed.
I usually find it easiest to check the new value of the text if the change were accepted. You want to optionally have a -
, followed by 1-9
with any number of digits after it. It's important to allow an empty string, else the user won't be able to delete everything.
So you probably need something like
UnaryOperator<Change> integerFilter = change -> {
String newText = change.getControlNewText();
if (newText.matches("-?([1-9][0-9]*)?")) {
return change;
}
return null;
};
myNumericField.setTextFormatter(
new TextFormatter<Integer>(new IntegerStringConverter(), 0, integerFilter));
You can even add more functionality to the filter to let it process -
in a smarter way, e.g.
UnaryOperator<Change> integerFilter = change -> {
String newText = change.getControlNewText();
// if proposed change results in a valid value, return change as-is:
if (newText.matches("-?([1-9][0-9]*)?")) {
return change;
} else if ("-".equals(change.getText()) ) {
// if user types or pastes a "-" in middle of current text,
// toggle sign of value:
if (change.getControlText().startsWith("-")) {
// if we currently start with a "-", remove first character:
change.setText("");
change.setRange(0, 1);
// since we're deleting a character instead of adding one,
// the caret position needs to move back one, instead of
// moving forward one, so we modify the proposed change to
// move the caret two places earlier than the proposed change:
change.setCaretPosition(change.getCaretPosition()-2);
change.setAnchor(change.getAnchor()-2);
} else {
// otherwise just insert at the beginning of the text:
change.setRange(0, 0);
}
return change ;
}
// invalid change, veto it by returning null:
return null;
};
This will let the user press -
at any point and it will toggle the sign of the integer.
SSCCE:
import java.util.function.UnaryOperator;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.control.TextFormatter;
import javafx.scene.control.TextFormatter.Change;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javafx.util.StringConverter;
import javafx.util.converter.IntegerStringConverter;
public class IntegerFieldExample extends Application {
@Override
public void start(Stage primaryStage) {
TextField integerField = new TextField();
UnaryOperator<Change> integerFilter = change -> {
String newText = change.getControlNewText();
if (newText.matches("-?([1-9][0-9]*)?")) {
return change;
} else if ("-".equals(change.getText()) ) {
if (change.getControlText().startsWith("-")) {
change.setText("");
change.setRange(0, 1);
change.setCaretPosition(change.getCaretPosition()-2);
change.setAnchor(change.getAnchor()-2);
return change ;
} else {
change.setRange(0, 0);
return change ;
}
}
return null;
};
// modified version of standard converter that evaluates an empty string
// as zero instead of null:
StringConverter<Integer> converter = new IntegerStringConverter() {
@Override
public Integer fromString(String s) {
if (s.isEmpty()) return 0 ;
return super.fromString(s);
}
};
TextFormatter<Integer> textFormatter =
new TextFormatter<Integer>(converter, 0, integerFilter);
integerField.setTextFormatter(textFormatter);
// demo listener:
textFormatter.valueProperty().addListener((obs, oldValue, newValue) -> System.out.println(newValue));
VBox root = new VBox(5, integerField, new Button("Click Me"));
root.setAlignment(Pos.CENTER);
Scene scene = new Scene(root, 300, 120);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
Tutorial
A comprehensive tutorial guide on using a TextFormatter
:
?
on the number group! Was thinking about-?([1-9]?|[1-9][0-9]*)
, but this is much cleaner! – Flea