ListView validate edit and prevent commit - javafx-8

Question

I'm using an editable ListView containing Patterns.
The user can see and edit the regexs in the list, and I'd like to validate whether the regex is syntactically correct before committing the value (and give feedback like a red border to the user).
Is there a way to do so?
patternList.setCellFactory(TextFieldListCell.forListView(new StringConverter<Pattern>() {
#Override
public String toString(Pattern pattern) {
return pattern.toString();
}
#Override
public Pattern fromString(String string) {
try {
return Pattern.compile(string);
} catch (PatternSyntaxException e) {
return null;
}
}
}));
patternList.setOnEditCommit(e -> {
if (e.getNewValue() == null) {
// TODO pattern syntax error, prevent commit and stay in edit mode
} else {
patternList.getItems().set(e.getIndex(), e.getNewValue());
}
});

Answer 1

I would do this by creating a TableCell implementation. E.g.:
import java.util.function.Predicate;
import javafx.beans.binding.Bindings;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.css.PseudoClass;
import javafx.scene.control.ContentDisplay;
import javafx.scene.control.TableCell;
import javafx.scene.control.TextField;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
public class ValidatingEditingCell<S> extends TableCell<S, String> {
private final TextField textField ;
private static final PseudoClass INVALID = PseudoClass.getPseudoClass("invalid");
private BooleanProperty valid = new SimpleBooleanProperty();
public ValidatingEditingCell(Predicate<String> validator) {
this.textField = new TextField();
valid.bind(Bindings.createBooleanBinding(() -> textField.getText() != null && validator.test(textField.getText()),
textField.textProperty()));
valid.addListener((obs, wasValid, isValid) -> {
pseudoClassStateChanged(INVALID, ! isValid);
});
pseudoClassStateChanged(INVALID, ! valid.get());
textField.addEventHandler(KeyEvent.KEY_PRESSED, e -> {
if (e.getCode() == KeyCode.ENTER && valid.get()) {
commitEdit(textField.getText());
}
if (e.getCode() == KeyCode.ESCAPE) {
cancelEdit();
}
});
setGraphic(textField);
setContentDisplay(ContentDisplay.TEXT_ONLY);
}
#Override
protected void updateItem(String item, boolean empty) {
super.updateItem(item, empty);
setText(empty ? null : item);
textField.setText(empty ? null : item);
setContentDisplay(isEditing() ? ContentDisplay.GRAPHIC_ONLY : ContentDisplay.TEXT_ONLY);
}
#Override
public void cancelEdit() {
super.cancelEdit();
setContentDisplay(ContentDisplay.TEXT_ONLY);
}
#Override
public void commitEdit(String newValue) {
super.commitEdit(newValue);
setContentDisplay(ContentDisplay.TEXT_ONLY);
}
#Override
public void startEdit() {
super.startEdit();
setContentDisplay(ContentDisplay.GRAPHIC_ONLY);
textField.selectAll();
textField.requestFocus();
}
}
This takes a predicate as an argument; the predicate returns true for valid text and false for invalid text. It sets a CSS pseudoclass on the cell, so you can use CSS to style the text field (or cell itself, if needed).
Here's a simple example which validates three different columns differently:
import java.util.function.Function;
import java.util.function.Predicate;
import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
public class ValidatingTableExample extends Application {
private static <S> TableColumn<S, String> column(String title, Function<S, StringProperty> property,
Predicate<String> validator) {
TableColumn<S, String> col = new TableColumn<>(title);
col.setCellValueFactory(cellData -> property.apply(cellData.getValue()));
col.setCellFactory(tc -> new ValidatingEditingCell<>(validator));
col.setPrefWidth(150);
return col ;
}
#Override
public void start(Stage primaryStage) {
TableView<Address> table = new TableView<>();
table.setEditable(true);
table.getColumns().add(column("City", Address::cityProperty, s -> ! s.isEmpty()));
table.getColumns().add(column("State", Address::stateProperty, s -> s.length()==2));
table.getColumns().add(column("Zip", Address::zipProperty, s -> s.matches("\\d{5}")));
Button newAddress = new Button("Add");
newAddress.setOnAction(e -> {
table.getItems().add(new Address("City", "State", "Zip"));
});
Button debug = new Button("Debug");
debug.setOnAction(e ->
table.getItems().stream()
.map(address -> String.format("%s, %s %s", address.getCity(), address.getState(), address.getZip()))
.forEach(System.out::println));
HBox buttons = new HBox(5, newAddress, debug);
buttons.setAlignment(Pos.CENTER);
buttons.setPadding(new Insets(5));
BorderPane root = new BorderPane(table, null, null, buttons, null);
Scene scene = new Scene(root, 600, 600);
scene.getStylesheets().add(getClass().getResource("validating-cell.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();
}
public static class Address {
private final StringProperty city = new SimpleStringProperty();
private final StringProperty state = new SimpleStringProperty();
private final StringProperty zip = new SimpleStringProperty();
public Address(String city, String state, String zip) {
setCity(city);
setState(state);
setZip(zip);
}
public final StringProperty cityProperty() {
return this.city;
}
public final String getCity() {
return this.cityProperty().get();
}
public final void setCity(final String city) {
this.cityProperty().set(city);
}
public final StringProperty stateProperty() {
return this.state;
}
public final String getState() {
return this.stateProperty().get();
}
public final void setState(final String state) {
this.stateProperty().set(state);
}
public final StringProperty zipProperty() {
return this.zip;
}
public final String getZip() {
return this.zipProperty().get();
}
public final void setZip(final String zip) {
this.zipProperty().set(zip);
}
}
public static void main(String[] args) {
launch(args);
}
}
and some sample CSS:
.table-cell:invalid .text-field {
-fx-focus-color: red ;
-fx-control-inner-background: #ffc0c0 ;
-fx-accent: red ;
}

Answer 2

I finally found a way, by overriding the commitEdit() method of TextFieldListCell:
patternList.setCellFactory(l -> new TextFieldListCell<Pattern>(new StringConverter<Pattern>() {
#Override
public String toString(Pattern pattern) {
return pattern.toString();
}
#Override
public Pattern fromString(String string) {
try {
return Pattern.compile(string);
} catch (PatternSyntaxException e) {
return null;
}
}
}) {
#Override
public void commitEdit(Pattern pattern) {
if (!isEditing()) return;
PseudoClass errorClass = PseudoClass.getPseudoClass("error");
pseudoClassStateChanged(errorClass, pattern == null);
if (pattern != null) {
super.commitEdit(pattern);
}
}
});
patternList.setOnEditCommit(e -> patternList.getItems().set(e.getIndex(), e.getNewValue()));