JavaFX - Filtered ComboBox

Question

I want a ComboBox, that filteres the list items as the user types. It should work as follow:

• When typing, the textfield should show one possible selection, b

Answer 1

Take a look:

import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.control.ComboBox;
import javafx.scene.control.TextField;

public class FilterComboBox extends ComboBox<String> {
    private ObservableList<String> initialList;
    private ObservableList<String> bufferList = FXCollections.observableArrayList();
    private String previousValue = "";

    public FilterComboBox(ObservableList<String> items) {
        super(items);
        super.setEditable(true);
        this.initialList = items;

        this.configAutoFilterListener();
    }

    private void configAutoFilterListener() {
        final FilterComboBox currentInstance = this;
        this.getEditor().textProperty().addListener(new ChangeListener<String>() {
            @Override
            public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
                previousValue = oldValue;
                final TextField editor = currentInstance.getEditor();
                final String selected = currentInstance.getSelectionModel().getSelectedItem();

                if (selected == null || !selected.equals(editor.getText())) {
                    filterItems(newValue, currentInstance);

                    currentInstance.show();
                    if (currentInstance.getItems().size() == 1) {
                        setUserInputToOnlyOption(currentInstance, editor);
                    }
                }
            }
        });
    }

    private void filterItems(String filter, ComboBox<String> comboBox) {
        if (filter.startsWith(previousValue) && !previousValue.isEmpty()) {
            ObservableList<String> filteredList = this.readFromList(filter, bufferList);
            bufferList.clear();
            bufferList = filteredList;
        } else {
            bufferList = this.readFromList(filter, initialList);
        }
        comboBox.setItems(bufferList);
    }

    private ObservableList<String> readFromList(String filter, ObservableList<String> originalList) {
        ObservableList<String> filteredList = FXCollections.observableArrayList();
        for (String item : originalList) {
            if (item.toLowerCase().startsWith(filter.toLowerCase())) {
                filteredList.add(item);
            }
        }

        return filteredList;
    }

    private void setUserInputToOnlyOption(ComboBox<String> currentInstance, final TextField editor) {
        final String onlyOption = currentInstance.getItems().get(0);
        final String currentText = editor.getText();
        if (onlyOption.length() > currentText.length()) {
            editor.setText(onlyOption);
            Platform.runLater(new Runnable() {
                @Override
                public void run() {
                    editor.selectRange(currentText.length(), onlyOption.length());
                }
            });
        }
    }
}

It is based on the answer that is found in this forum. Hope this helps.

Answer 2

As far as the filtering of the drop down is concerned. Isn't wrapping the list of possible options in a FilteredList the best solution?

MCVE:

import javafx.application.Application;
import javafx.application.Platform;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.collections.transformation.FilteredList;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class MCVE extends Application {
    public void start(Stage stage) {
        HBox root = new HBox();

        ComboBox<String> cb = new ComboBox<String>();
        cb.setEditable(true);

        // Create a list with some dummy values.
        ObservableList<String> items = FXCollections.observableArrayList("One", "Two", "Three", "Four", "Five", "Six",
                "Seven", "Eight", "Nine", "Ten");

        // Create a FilteredList wrapping the ObservableList.
        FilteredList<String> filteredItems = new FilteredList<String>(items, p -> true);

        // Add a listener to the textProperty of the combobox editor. The
        // listener will simply filter the list every time the input is changed
        // as long as the user hasn't selected an item in the list.
        cb.getEditor().textProperty().addListener((obs, oldValue, newValue) -> {
            final TextField editor = cb.getEditor();
            final String selected = cb.getSelectionModel().getSelectedItem();

            // This needs run on the GUI thread to avoid the error described
            // here: https://bugs.openjdk.java.net/browse/JDK-8081700.
            Platform.runLater(() -> {
                // If the no item in the list is selected or the selected item
                // isn't equal to the current input, we refilter the list.
                if (selected == null || !selected.equals(editor.getText())) {
                    filteredItems.setPredicate(item -> {
                        // We return true for any items that starts with the
                        // same letters as the input. We use toUpperCase to
                        // avoid case sensitivity.
                        if (item.toUpperCase().startsWith(newValue.toUpperCase())) {
                            return true;
                        } else {
                            return false;
                        }
                    });
                }
            });
        });

        cb.setItems(filteredItems);

        root.getChildren().add(cb);

        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }

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

Answer 3

I searched similar for a while and found this. Take a look:

public class AutoCompleteComboBoxListener<T> implements EventHandler<KeyEvent> {

    private ComboBox comboBox;
    private StringBuilder sb;
    private ObservableList<T> data;
    private boolean moveCaretToPos = false;
    private int caretPos;

    public AutoCompleteComboBoxListener(final ComboBox comboBox) {
        this.comboBox = comboBox;
        sb = new StringBuilder();
        data = comboBox.getItems();

        this.comboBox.setEditable(true);
        this.comboBox.setOnKeyPressed(new EventHandler<KeyEvent>() {

            @Override
            public void handle(KeyEvent t) {
                comboBox.hide();
            }
        });
        this.comboBox.setOnKeyReleased(AutoCompleteComboBoxListener.this);
    }

    @Override
    public void handle(KeyEvent event) {
        ListView lv = ((ComboBoxListViewSkin) comboBox.getSkin()).getListView();

        if(event.getCode() == KeyCode.UP) {
            caretPos = -1;
            moveCaret(comboBox.getEditor().getText().length());
            return;
        } else if(event.getCode() == KeyCode.DOWN) {
            if(!comboBox.isShowing()) {
                comboBox.show();
            }
            caretPos = -1;
            moveCaret(comboBox.getEditor().getText().length());
            return;
        } else if(event.getCode() == KeyCode.BACK_SPACE) {
            moveCaretToPos = true;
            caretPos = comboBox.getEditor().getCaretPosition();
        } else if(event.getCode() == KeyCode.DELETE) {
            moveCaretToPos = true;
            caretPos = comboBox.getEditor().getCaretPosition();
        }

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

        ObservableList list = FXCollections.observableArrayList();
        for (int i=0; i<data.size(); i++) {
            if(data.get(i).toString().toLowerCase().startsWith(
                AutoCompleteComboBoxListener.this.comboBox
                .getEditor().getText().toLowerCase())) {
                list.add(data.get(i));
            }
        }
        String t = comboBox.getEditor().getText();

        comboBox.setItems(list);
        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;
    }

}

You can call it with

new AutoCompleteComboBoxListener<>(comboBox);

---

It's based on this and I customized it to fit my needs.

Feel free to use it and if anybody can improve it, tell me.