【发布时间】：2016-05-15 02:54:45
【问题描述】：
我已经实现了一个ComboBox，它的列表由ComboBoxTextField 中的输入过滤。它的工作方式与您可能期望此类控件的过滤器工作一样。列表中以输入文本开头的每个项目都会显示在列表中。
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字符之外的任何其他字符，则整个字符串都会被删除。只有当这是我在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，或者如果我第二次选择一个项目，则不会出现所描述的问题。
对我来说真正奇怪的是，这些问题似乎是由设置的谓词引起的（如果我注释掉 setPredicate 的调用，一切正常）。这很奇怪，因为我认为这只会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();
ComboBox<ComboBoxItem> cb = new ComboBox<ComboBoxItem>();
cb.setEditable(true);
cb.setConverter(new StringConverter<ComboBoxItem>() {
@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));
}
});
ObservableList<ComboBoxItem> 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"));
FilteredList<ComboBoxItem> filteredOptions = new FilteredList<ComboBoxItem>(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 ChangeListener<String> {
private ComboBox<ComboBoxItem> box;
private FilteredList<ComboBoxItem> items;
public InputFilter(ComboBox<ComboBoxItem> box, FilteredList<ComboBoxItem> items) {
this.box = box;
this.items = items;
}
@Override
public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
String value = newValue;
// If any item is selected we get the first word of that item.
String selected = box.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：我试图覆盖关键侦听器以拼命尝试解决问题：
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();
});
遗憾的是，这也不能解决问题。如果我例如选择“三是数字”项，然后尝试删除“三”中的最后一个“e”，这是文本属性将在其中切换的值：
TextProperty: Three is a number
TextPropery: Thre is a number
TextPropery:
所以它首先删除了正确的字符，但后来由于某种原因它删除了整个String。如前所述，这只是因为已经设置了谓词，并且仅在我第一次选择项目后进行第一次输入时才会发生。
【问题讨论】：
标签： java javafx filter combobox predicate