ComboBox field empties upon changing selection however value is not null

[Yosuf Ibrahim]

Hello, so basically I have multiple combo boxes which are filled with data pulled from MySQL database
However, there is this type of box where when I change selection the text disappears
I tested to see if the value changes to null because the field is empty however the value returned is always the selected item and everything works fine so it seems to me like a bug however I thought I should still ask for help because I am probably looking at it wrong

This is how I populate my ComboBox

    private static void setComboBoxConvertor(ComboBox<Supplier> comboBox){
        comboBox.setConverter(new StringConverter<>() {
            @Override
            public String toString(Supplier supplier) {
                return supplier != null ? supplier.toString() : "";
            }

            @Override
            public Supplier fromString(String string) {
                if (string == null) {
                    return null;
                }
                Pattern pattern = Pattern.compile("\\d+");
                Matcher matcher = pattern.matcher(string);
                if (matcher.find())
                    return SQL_Supplier.sql_readFromDB(Integer.parseInt(matcher.group()));
                else
                    throw new IllegalArgumentException("Supplier ID is not available in string");
            }
        });
    }

    public static void initializeComboBox(ComboBox<Supplier> comboBox) {
        comboBox.setItems(SQL_Supplier.sql_readFromDB());
        FX_Utilities.filteredComboBoxManager(comboBox, (typedText, itemToCompare) -> itemToCompare.toString().toLowerCase().contains(typedText.toLowerCase()));
        setComboBoxConvertor(comboBox);
    }

I have multiple other ComboBox which store types other than Suppliers and they all work fine, they all use the same filteredComboBoxManager method as well however each has it's own setComboBoxConvertor.

Thank you again in advance

[Yosuf Ibrahim]

I am still stuck on this guys

[Lou Hamers]

FX_Utilities.filteredComboBoxManager() - no code, not sure what this is doing.

Is this "Supplier" the standard Java functional interface Supplier, or your own type? You probably want to use a type of your own as your ComboBox item type, and implement toString(); it could implement the Supplier interface too, if useful. Also/or this might be fixed by setting a cell factory on the ComboBox. Basically the CB needs to know how to render the items it's listing - that's not always "free" functionality.

If you want a for-certain answer you may need to add a complete example starting from something like this so we can see exactly what you're seeing:

public class ComboBoxTest extends Application {
    
    public static void main(String[] args) {
        launch();
    }
    
    @Override
    public void start(Stage stage) throws Exception {
        ComboBox<ModelClass> cb = new ComboBox<>();
        
        initializeComboBox(cb);
        
        Scene scene = new Scene(new VBox(cb), 640, 480);
        stage.setScene(scene);
        stage.show();
    }
}

I have multiple other ComboBox which store types other than Suppliers and they all work fine

Might have started to answer your own question there.

[Lou Hamers]

Yosuf Ibrahim wrote:I am still stuck on this guys

Yeah not sure where the other ranchers are lately. Usually some of the others will pop into this remote frontier JavaFX ranch to see if I'm still alive living all alone out here. Sometimes the native code tribes get restless and come around looking for trouble... angry folk, they all still use C and C++. Guess I can't blame them with us VM-based ranchers moving in on their territory...

[Yosuf Ibrahim]

Lou Hamers wrote:FX_Utilities.filteredComboBoxManager() - no code, not sure what this is doing.

Yeah lol sorry, there you go, I took this function from stack overflow to allow for filtering my combo box result as the user is typing in. I edited a small chunk of it a long time ago but I do not even remember what is in there, it works perfectly though

public static<T> void filteredComboBoxManager(ComboBox<T> comboBox, AutoCompleteComparator<T> comparatorMethod) {
		ObservableList<T> data = comboBox.getItems();

		comboBox.setEditable(true);
		comboBox.setVisibleRowCount(data.size());
		comboBox.getEditor().focusedProperty().addListener(observable -> {
			if (comboBox.getSelectionModel().getSelectedIndex() < 0) {
				comboBox.getEditor().setText(null);
			}
		});
		comboBox.addEventHandler(KeyEvent.KEY_PRESSED, keyEvent -> comboBox.hide());
		comboBox.addEventHandler(KeyEvent.KEY_RELEASED, new EventHandler<>() {

			private boolean moveCaretToPos = false;
			private int caretPos;

			@Override
			public void handle(KeyEvent event) {
				if (event.getCode() == KeyCode.UP) {
					caretPos = -1;
					if (comboBox.getEditor().getText() != null) {
						moveCaret(comboBox.getEditor().getText().length());
					}
					return;
				} else if (event.getCode() == KeyCode.DOWN) {
					if (!comboBox.isShowing()) {
						comboBox.show();
					}
					caretPos = -1;
					if (comboBox.getEditor().getText() != null) {
						moveCaret(comboBox.getEditor().getText().length());
					}
					return;
				} else if (event.getCode() == KeyCode.BACK_SPACE) {
					if (comboBox.getEditor().getText() != null) {
						moveCaretToPos = true;
						caretPos = comboBox.getEditor().getCaretPosition();
					}
				} else if (event.getCode() == KeyCode.DELETE) {
					if (comboBox.getEditor().getText() != null) {
						moveCaretToPos = true;
						caretPos = comboBox.getEditor().getCaretPosition();
					}
				} else if (event.getCode() == KeyCode.ENTER) {
					return;
				}

				if (event.getCode() == KeyCode.RIGHT || event.getCode() == KeyCode.LEFT || event.getCode().equals(KeyCode.SHIFT) || event.getCode().equals(KeyCode.CONTROL)
						|| event.isControlDown() || event.getCode() == KeyCode.HOME || event.getCode() == KeyCode.END
						|| event.getCode() == KeyCode.TAB || event.getCode() == KeyCode.ESCAPE) {
					return;
				}

				ObservableList<T> list = FXCollections.observableArrayList();
				for (T aData : data) {
					if (aData != null && comboBox.getEditor().getText() != null && comparatorMethod.matches(comboBox.getEditor().getText(), aData)) {
						list.add(aData);
					}
				}
				String t = "";
				if (comboBox.getEditor().getText() != null) {
					t = comboBox.getEditor().getText();
				}

				comboBox.setItems(list);
				comboBox.hide();
				comboBox.show();
				comboBox.getEditor().setText(t);
				if (!moveCaretToPos) {
					caretPos = -1;
				}
				moveCaret(t.length());
				if (!list.isEmpty()) {
					comboBox.show();
				}
			}

			private void moveCaret(int textLength) {
				if (caretPos == -1) {
					comboBox.getEditor().positionCaret(textLength);
				} else {
					comboBox.getEditor().positionCaret(caretPos);
				}
				moveCaretToPos = false;
			}
		});
	}

Lou Hamers wrote:
Is this "Supplier" the standard Java functional interface Supplier, or your own type? You probably want to use a type of your own as your Combo Box item type, and implement toString(); it could implement the Supplier interface too, if useful. Also/or this might be fixed by setting a cell factory on the Combo Box. Basically the CB needs to know how to render the items it's listing - that's not always "free" functionality.

If you want a for-certain answer you may need to add a complete example starting from something like this so we can see exactly what you're seeing:

I have multiple other ComboBox which store types other than Suppliers and they all work fine

Might have started to answer your own question there.

Supplier class is not the standard java, it is my own. I tried to recreate a complete example of what is happening in a separate project but I am not getting the same error anymore which is even more confusing since all I did different is instead of pulling the Supplier from the database I created them in the Main class, which probably means there is something else. I will try to read from the database in my temp project as well and see if I get the same results or not

package mainApp;

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.StringConverter;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main extends Application {

    public static void main(String[] args) {
          launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        Supplier a = new Supplier(1000, "Supplier a", "01023698547", "This is the first supplier");
        Supplier b = new Supplier(1001, "Supplier b", "01125465489", "This is the second supplier");
        Supplier c = new Supplier(1002, "Supplier c", "01254654988", "This is the third supplier");
        Supplier d = new Supplier(1003, "Supplier d", "01554654889", "This is the fourth supplier");

        Supplier.suppliers.add(a);
        Supplier.suppliers.add(b);
        Supplier.suppliers.add(c);
        Supplier.suppliers.add(d);


        primaryStage.setTitle("Hello World!");
        Button btn = new Button();
        btn.setPrefSize(50,50);
        btn.setText("Say 'Hello World'");
        btn.setOnAction(event -> System.out.println("Hello World!"));

        ComboBox<Supplier> supplierComboBox = new ComboBox<>();
        Supplier.initializeComboBox(supplierComboBox);

        StackPane root = new StackPane();
        root.getChildren().add(btn);
        root.getChildren().add(supplierComboBox);

        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
    }

    public enum PersonType {
        SUPPLIER, CUSTOMER, EMPLOYEE;

    }

    public abstract class Person {

        private final Integer id;
        private final String name;
        private final String phoneNum;
        private final String notes;
        private final PersonType type;


        public Person(Integer id, String name, String phoneNum, String notes, PersonType type) {
            this.id = id;
            this.name = name;
            this.phoneNum = phoneNum;
            this.notes = notes;
            this.type = type;
        }

        @Override
        public String toString() {
            return String.format("(%s)-%s", id, name);
        }

        public String getName() {
            return name;
        }

        public String getPhoneNum() {
            return phoneNum;
        }

        public Integer getId() {
            return id;
        }

        public String getNotes() {
            return notes;
        }

        public PersonType getType() {
            return type;
        }
    }

    public class Supplier extends Person {

        public static List<Supplier> suppliers = new ArrayList<>();

        public Supplier(int id, String name, String phoneNum, String notes) {
            super(id, name, phoneNum, notes, PersonType.SUPPLIER);
        }

        public static Supplier findSupplier(Integer code) {
            for (Supplier s: suppliers) {
                if (Objects.equals(s.getId(), code))
                    return s;
            }
            return null;
        }

        private static void setComboBoxConvertor(ComboBox<Supplier> comboBox) {
            comboBox.setConverter(new StringConverter<>() {
                @Override
                public String toString(Supplier supplier) {
                    return supplier != null ? supplier.toString() : "";
                }

                @Override
                public Supplier fromString(String string) {
                    if (string == null) {
                        return null;
                    }
                    Pattern pattern = Pattern.compile("\\d+");
                    Matcher matcher = pattern.matcher(string);
                    if (matcher.find())
                        return findSupplier(Integer.parseInt(matcher.group()));
                    else
                        throw new IllegalArgumentException("Supplier ID is not available in string");
                }
            });
        }

        public static void initializeComboBox(ComboBox<Supplier> comboBox) {
            comboBox.setItems(FXCollections.observableList(suppliers));
            filteredComboBoxManager(comboBox, (typedText, itemToCompare) -> itemToCompare.toString().toLowerCase().contains(typedText.toLowerCase()));
            setComboBoxConvertor(comboBox);
        }

        public interface AutoCompleteComparator<T> {
            boolean matches(String typedText, T objectToCompare);
        }

        public static<T> void filteredComboBoxManager(ComboBox<T> comboBox, AutoCompleteComparator<T> comparatorMethod) {
            ObservableList<T> data = comboBox.getItems();

            comboBox.setEditable(true);
            comboBox.setVisibleRowCount(data.size());
            comboBox.getEditor().focusedProperty().addListener(observable -> {
                if (comboBox.getSelectionModel().getSelectedIndex() < 0) {
                    comboBox.getEditor().setText(null);
                }
            });
            comboBox.addEventHandler(KeyEvent.KEY_PRESSED, keyEvent -> comboBox.hide());
            comboBox.addEventHandler(KeyEvent.KEY_RELEASED, new EventHandler<>() {

                private boolean moveCaretToPos = false;
                private int caretPos;

                @Override
                public void handle(KeyEvent event) {
                    if (event.getCode() == KeyCode.UP) {
                        caretPos = -1;
                        if (comboBox.getEditor().getText() != null) {
                            moveCaret(comboBox.getEditor().getText().length());
                        }
                        return;
                    } else if (event.getCode() == KeyCode.DOWN) {
                        if (!comboBox.isShowing()) {
                            comboBox.show();
                        }
                        caretPos = -1;
                        if (comboBox.getEditor().getText() != null) {
                            moveCaret(comboBox.getEditor().getText().length());
                        }
                        return;
                    } else if (event.getCode() == KeyCode.BACK_SPACE) {
                        if (comboBox.getEditor().getText() != null) {
                            moveCaretToPos = true;
                            caretPos = comboBox.getEditor().getCaretPosition();
                        }
                    } else if (event.getCode() == KeyCode.DELETE) {
                        if (comboBox.getEditor().getText() != null) {
                            moveCaretToPos = true;
                            caretPos = comboBox.getEditor().getCaretPosition();
                        }
                    } else if (event.getCode() == KeyCode.ENTER) {
                        return;
                    }

                    if (event.getCode() == KeyCode.RIGHT || event.getCode() == KeyCode.LEFT || event.getCode().equals(KeyCode.SHIFT) || event.getCode().equals(KeyCode.CONTROL)
                            || event.isControlDown() || event.getCode() == KeyCode.HOME || event.getCode() == KeyCode.END
                            || event.getCode() == KeyCode.TAB || event.getCode() == KeyCode.ESCAPE) {
                        return;
                    }

                    ObservableList<T> list = FXCollections.observableArrayList();
                    for (T aData : data) {
                        if (aData != null && comboBox.getEditor().getText() != null && comparatorMethod.matches(comboBox.getEditor().getText(), aData)) {
                            list.add(aData);
                        }
                    }
                    String t = "";
                    if (comboBox.getEditor().getText() != null) {
                        t = comboBox.getEditor().getText();
                    }

                    comboBox.setItems(list);
                    comboBox.hide();
                    comboBox.show();
                    comboBox.getEditor().setText(t);
                    if (!moveCaretToPos) {
                        caretPos = -1;
                    }
                    moveCaret(t.length());
                    if (!list.isEmpty()) {
                        comboBox.show();
                    }
                }

                private void moveCaret(int textLength) {
                    if (caretPos == -1) {
                        comboBox.getEditor().positionCaret(textLength);
                    } else {
                        comboBox.getEditor().positionCaret(caretPos);
                    }
                    moveCaretToPos = false;
                }
            });
        }


    }

}

[Tim Holloway]

Lou Hamers wrote:

Yosuf Ibrahim wrote:I am still stuck on this guys

Yeah not sure where the other ranchers are lately. Usually some of the others will pop into this remote frontier JavaFX ranch to see if I'm still alive living all alone out here. Sometimes the native code tribes get restless and come around looking for trouble... angry folk, they all still use C and C++. Guess I can't blame them with us VM-based ranchers moving in on their territory...

Actually, it's more to do with the fact that we don't get paid to do this, so we check in when we aren't otherwise doing our full-time jobs, home maintenance, watching TV or whatever. The Ranch is not the place to come for "instant answers". To get that level of service costs money.

So yes, I spent the last 4 hours elsewhere, doing yard maintenance before the next killer heatwave sets in, corresponding with a client, and eating more than I should.

Also, in my case, I've never worked with JavaFX. so any advice I give here is necessarily general in nature. JavaFX doesn't have a lot of support at the moment, though,

As far as general advice goes, however, that code smells to me like it's trying to do too much. In most GUI systems, a lot of those things would be automatically done by the GUI framework itself. So it's possible that simplifying the code might actually make it work better.

[Lou Hamers]

Haha, yeah I know Tim, I'm no different (other than having the uncommon JFX background I guess).

[Lou Hamers]

Yosuf Ibrahim wrote:
Supplier class is not the standard java, it is my own. I tried to recreate a complete example of what is happening in a separate project but I am not getting the same error anymore which is even more confusing since all I did different is instead of pulling the Supplier from the database I created them in the Main class, which probably means there is something else. I will try to read from the database in my temp project as well and see if I get the same results or not

Aha, it sounds like you're on the trail of the problem then. That's one of the nice things about this technique of reproducing the problem in a smaller example. Every so often the code you think SHOULD reproduce it doesn't, which tells you that the problem is somewhere you haven't been looking. Usually shortly after that happens you find the problem yourself without posting the question publicly.

Maybe whatever you think is coming from the database/datasource is not what you're expecting?

[Yosuf Ibrahim]

Wow I got stuck with trying to get an event handler that only gets fired when a selection has been made and somehow Google brought me back here :P

My post is famous.

[Yosuf Ibrahim]

Wow I got stuck with trying to get an event handler that only gets fired when a selection has been made and somehow Google brought me back here :P

My post is famous.