我已经实现了一个ComboBox,其列表由ComboBox TextField中的输入过滤.它可以正常工作,因为你可能期望这种控件的过滤器工作.列表中显示列表中以输入文本开头的每个项目.

我只有一个小问题.如果我从列表中选择一个项目,然后尝试删除文本字段中的最后一个字符,则没有任何反应.如果我从列表中选择一个项目,然后尝试删除除最后一个之外的任何其他字符,则会删除整个字符串.只有这是我在ComboBox中做的第一件事时才会出现这两个问题.如果我先在组合框中写一些东西,或者我第二次选择一个项目,则不会出现所描述的任何问题.

对我来说真正奇怪的是,这些问题似乎是由谓词设置引起的(如果我注释掉setPredicate的调用,一切正常).这很奇怪,因为我认为这应该只影响为谓词设置的列表.它不应该影响ComboBox的其余部分.

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
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.layout.VBox;
import javafx.stage.Stage;
import javafx.util.StringConverter;
public class TestInputFilter extends Application {
    public void start(Stage stage) {
        VBox root = new VBox();
        ComboBoxBoxItem> cb = new ComboBoxBoxItem>();
        cb.setEditable(true);
        cb.setConverter(new StringConverterBoxItem>() {
            @Override
            // To convert the ComboBoxItem to a String we just call its
            // toString() method.
            public String toString(ComboBoxItem object) {
                return object == null ? null : object.toString();
            }
            @Override
            // To convert the String to a ComboBoxItem we loop through all of
            // the items in the comboBox dropdown and select anyone that starts
            // with the String. If we don't find a match we create our own
            // ComboBoxItem.
            public ComboBoxItem fromString(String string) {
                return cb.getItems().stream().filter(item -> item.getText().startsWith(string)).findFirst()
                        .orElse(new ComboBoxItem(string));
            }
        });
        ObservableListBoxItem> options = FXCollections.observableArrayList(new ComboBoxItem("One is a number"),new ComboBoxItem("Two is a number"),new ComboBoxItem("Three is a number"),new ComboBoxItem("Four is a number"),new ComboBoxItem("Five is a number"),new ComboBoxItem("Six is a number"),new ComboBoxItem("Seven is a number"));
        FilteredListBoxItem> filteredOptions = new FilteredListBoxItem>(options,p -> true);
        cb.setItems(filteredOptions);
        InputFilter inputFilter = new InputFilter(cb,filteredOptions);
        cb.getEditor().textProperty().addListener(inputFilter);
        root.getChildren().add(cb);
        stage.setScene(new Scene(root));
        stage.show();
    }
    public static void main(String[] args) {
        launch();
    }
    class ComboBoxItem {
        private String text;
        public ComboBoxItem(String text) {
            this.text = text;
        }
        public String getText() {
            return text;
        }
        @Override
        public String toString() {
            return text;
        }
    }
    class InputFilter implements ChangeListenerBoxBoxItem> Box;
        private FilteredListBoxItem> items;
        public InputFilter(ComboBoxBoxItem> Box,FilteredListBoxItem> items) {
            this.Box = Box;
            this.items = items;
        }
        @Override
        public void changed(ObservableValueBox.getSelectionModel().getSelectedItem() != null
                    ? Box.getSelectionModel().getSelectedItem().getText() : null;
            // If an item is selected and the value of in the editor is the same
            // as the selected item we don't filter the list.
            if (selected != null && value.equals(selected)) {
                items.setPredicate(item -> {
                    return true;
                });
            } else {
                items.setPredicate(item -> {
                    if (item.getText().toUpperCase().startsWith(value.toUpperCase())) {
                        return true;
                    } else {
                        return false;
                    }
                });
            }
        }
    }
}

编辑：我试图在绝望的尝试中覆盖关键监听器来解决问题：

cb.getEditor().addEventFilter(KeyEvent.KEY_PRESSED,e -> {
    TextField editor = cb.getEditor();
    int caretPos = cb.getEditor().getCaretPosition();
    StringBuilder text = new StringBuilder(cb.getEditor().getText());
    // If BACKSPACE is pressed we remove the character at the index
    // before the caret position.
    if (e.getCode().equals(KeyCode.BACK_SPACE)) {
        // BACKSPACE should only remove a character if the caret
        // position isn't zero.
        if (caretPos > 0) {
            text.deleteCharAt(--caretPos);
        }
        e.consume();
    }
    // If DELETE is pressed we remove the character at the caret
    // position.
    else if (e.getCode().equals(KeyCode.DELETE)) {
        // DELETE should only remove a character if the caret isn't
        // positioned after that last character in the text.
        if (caretPos < text.length()) {
            text.deleteCharAt(caretPos);
        }
    }
    // If LEFT key is pressed we move the caret one step to the left.
    else if (e.getCode().equals(KeyCode.LEFT)) {
        caretPos--;
    }
    // If RIGHT key is pressed we move the caret one step to the right.
    else if (e.getCode().equals(KeyCode.RIGHT)) {
        caretPos++;
    }
    // Otherwise we just add the key text to the text.
    // TODO We are currently not handling UP/DOWN keys (should move
    // caret to the end/beginning of the text).
    // TODO We are currently not handling keys that doesn't represent
    // any symbol,like ALT. Since they don't have a text,they will
    // just move the caret one step to the right. In this case,that
    // caret should just hold its current position.
    else {
        text.insert(caretPos++,e.getText());
        e.consume();
    }
    final int finalPos = caretPos;
    // We set the editor text to the new text and finally we move the
    // caret to its new position.
    editor.setText(text.toString());
    Platform.runLater(() -> editor.positionCaret(finalPos));
});
// We just consume KEY_RELEASED and KEY_TYPED since we don't want to
// have duplicated input.
cb.getEditor().addEventFilter(KeyEvent.KEY_RELEASED,e -> {
    e.consume();
});
cb.getEditor().addEventFilter(KeyEvent.KEY_TYPED,e -> {
    e.consume();
});

可悲的是,这也没有解决问题.如果我选择“Three is a number”项,然后尝试删除“Three”中的最后一个“e”,这是text属性将在之间切换的值：

TextProperty: Three is a number
TextPropery: Thre is a number
TextPropery: 

所以它首先删除了正确的字符,但是由于某种原因它删除了整个字符串.如前所述,这只是因为谓词已经设置,而且只有在我第一次选择项目后进行第一次输入时才会发生这种情况.