【发布时间】：2016-06-27 16:22:14
【问题描述】：
我的一位开发人员尝试将 ComboBox 扩展为根据用户类型进行自动过滤：
public class AutoCompleteComboBox<T> extends ComboBox<T> {
private FilteredList<T> filteredItems;
private SortedList<T> sortedItems;
public AutoCompleteComboBox() {
setEditable(true);
setOnKeyReleased(e -> handleOnKeyReleasedEvent(e));
setOnMouseClicked(e -> handleOnMouseClicked(e));
}
private void handleOnMouseClicked(MouseEvent e) {
getItems().stream()
.filter(item -> item.toString().equals(getEditor().getText()))
.forEach(item -> getSelectionModel().select(item));
setCaretPositionToEnd();
}
private void handleOnKeyReleasedEvent(KeyEvent e) {
if (e.getCode() == KeyCode.UP || e.getCode() == KeyCode.DOWN) {
getItems().stream()
.filter(item -> item.toString().equals(getEditor().getText()))
.forEach(item -> getSelectionModel().select(item));
show();
setCaretPositionToEnd();
} else if (e.getCode() == KeyCode.ENTER || e.getCode() == KeyCode.TAB) {
String editorStr = getEditor().getText();
getSelectionModel().clearSelection();
getEditor().setText(editorStr);
setItems(this.sortedItems);
getItems().stream()
.filter(item -> item.toString().equals(editorStr))
.forEach(item -> getSelectionModel().select(item));
getEditor().selectEnd();
if (e.getCode() == KeyCode.ENTER) {
getEditor().deselect();
}
hide();
} else if (e.getText().length() == 1) {
getSelectionModel().clearSelection();
if (getEditor().getText().length() == 0) {
getEditor().setText(e.getText());
}
filterSelectionList();
show();
} else if (e.getCode() == KeyCode.BACK_SPACE && getEditor().getText().length() > 0) {
String editorStr = getEditor().getText();
getSelectionModel().clearSelection();
getEditor().setText(editorStr);
int beforeFilter = getItems().size();
filterSelectionList();
int afterFilter = getItems().size();
if (afterFilter > beforeFilter) {
hide();
}
show();
} else if (e.getCode() == KeyCode.BACK_SPACE && getEditor().getText().length() == 0) {
clearSelection();
hide();
show();
}
}
private void filterSelectionList() {
setFilteredItems();
setCaretPositionToEnd();
}
private void setFilteredItems() {
filteredItems.setPredicate(item ->
item.toString().toLowerCase().startsWith(getEditor().getText().toLowerCase()));
}
private void setCaretPositionToEnd() {
getEditor().selectEnd();
getEditor().deselect();
}
public void setInitItems(ObservableList<T> values) {
filteredItems = new FilteredList<>(values);
sortedItems = new SortedList<>(filteredItems);
setItems(this.sortedItems);
}
public void clearSelection() {
getSelectionModel().clearSelection();
getEditor().clear();
if (this.filteredItems != null) {
this.filteredItems.setPredicate(item -> true);
}
}
public T getSelectedItem() {
T selectedItem = null;
if (getSelectionModel().getSelectedIndex() > -1) {
selectedItem = getItems().get(getSelectionModel().getSelectedIndex());
}
return selectedItem;
}
public void select(String value) {
if (!value.isEmpty()) {
getItems().stream()
.filter(item -> value.equals(item.toString()))
.findFirst()
.ifPresent(item -> getSelectionModel().select(item));
}
}
}
控件工作得很好，直到我将某些东西绑定到 Selected 或 Value 属性。一旦发生这种情况，一旦我尝试离开该字段（或按 Enter 键导致该操作发生），我将收到以下异常。 （只需用鼠标选择值就不会出现问题）我在此控件中绑定的是 CodeTableValue 的简单对象 - 它有两个属性 - 字符串、代码和值。 toString 返回 Value 属性。
如果控件只是在没有任何侦听器的情况下设置，它就可以正常工作。但是，一旦我听到其中一个属性的值，它就会失败。
当我在课堂上使用AutoCompleteComboBox 控件时：
@FXML private AutoCompleteComboBox<CodeTableValue> myAutoCompleteBox;
myAutoCompleteBox.getSelectionModel().selectedItemProperty().addListener((obs, ov, nv) -> {
System.out.println(nv);
});
抛出的异常：
Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: java.lang.String cannot be cast to cache.CodeTableValue
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:361)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.ReadOnlyObjectPropertyBase.fireValueChangedEvent(ReadOnlyObjectPropertyBase.java:74)
at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:102)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
at javafx.scene.control.SelectionModel.setSelectedItem(SelectionModel.java:102)
at javafx.scene.control.ComboBox.lambda$new$152(ComboBox.java:249)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:361)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
at javafx.scene.control.ComboBoxBase.setValue(ComboBoxBase.java:150)
at com.sun.javafx.scene.control.skin.ComboBoxPopupControl.setTextFromTextFieldIntoComboBoxValue(ComboBoxPopupControl.java:405)
at com.sun.javafx.scene.control.skin.ComboBoxPopupControl.lambda$new$291(ComboBoxPopupControl.java:82)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:361)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7718)
at javafx.scene.Node.setFocused(Node.java:7771)
at javafx.scene.Scene$KeyHandler.setWindowFocused(Scene.java:3932)
at javafx.scene.Scene$KeyHandler.lambda$new$11(Scene.java:3954)
at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:103)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:144)
at javafx.stage.Window.setFocused(Window.java:439)
at com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:59)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:100)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:40)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.lambda$handleWindowEvent$423(GlassWindowEventHandler.java:150)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:148)
at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1266)
at com.sun.glass.ui.Window.notifyFocus(Window.java:1245)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)
如果 editableFlag 为 false，则此方法有效。当我们允许用户在组合框中输入内容来过滤内容时，就会发生这种情况。如果没有绑定，我们不会出现异常，并且值设置正确。
我一直在深入研究这个异常，它被抛出在这里：
com.sun.javafx.binding.ExpressionHelper.Generic.fireValueChangedEvent()
if (curChangeSize > 0) {
final T oldValue = currentValue;
currentValue = observable.getValue();
final boolean changed = (currentValue == null)? (oldValue != null) : !currentValue.equals(oldValue);
if (changed) {
for (int i = 0; i < curChangeSize; i++) {
try {
curChangeList[i].changed(observable, oldValue, currentValue);
} catch (Exception e) {
Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
}
}
}
}
只有在绑定了 valueProperty 或 selectedItemProperty 时才从这里来。否则我们不会得到这个问题。
javafx.beans.property.ObjectPropertyBase.set(T) @Override
public void set(T newValue) {
if (isBound()) {
throw new java.lang.RuntimeException((getBean() != null && getName() != null ?
getBean().getClass().getSimpleName() + "." + getName() + " : ": "") + "A bound value cannot be set.");
}
if (value != newValue) {
value = newValue;
markInvalid();
}
}
我已尝试将 StringConverter 添加到编辑器中，以查看是否可以解决问题，但它再次抛出此异常。也许我们正试图错误地处理这一切？
基本上，我们希望在用户输入字段时过滤组合框选择项。如果我们应该以不同的方式处理这个问题，请告诉我，但目前，我认为这可能是 JDK 中的一个错误？如果该字段未绑定，那么我们没有问题，但是一旦绑定，当该字段失去焦点或按下回车键时会发生此异常。
【问题讨论】：