JavaFX ComboBox的错误？-Java 学习之路

我的一位开发人员试图根据用户输入的内容将ComboBox扩展为自动过滤器：

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));
        }
    }
}

控件工作正常，直到我将某些内容绑定到Selected或Value属性 . 一旦发生这种情况，一旦我尝试离开现场（或点击输入导致动作发生），我得到以下异常 . （只需用鼠标选择值就没有问题）我在这个控件中绑定的是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 .

如果控件刚刚设置没有任何监听器，它就可以正常工作 . 但是一旦我听到其中一个属性值，它就失败了 .

当我在班上使用 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 . 当我们允许用户键入组合框以过滤内容时，就会发生这种情况 . 没有绑定，我们没有例外，并且值被正确设置 .

我一直在深入研究这个异常，它被抛到这里：

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);
                            }
                        }
                    }
                }

它仅在绑定valueProperty或selectedItemProperty时才会出现 . 否则我们不会遇到这个问题 .

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();
        }
    }

我试图将StringConverter添加到编辑器中以查看是否可以解决问题，但同样，它会继续抛出此异常 . 也许我们试图处理这一切都错了？

基本上我们希望在用户键入字段时过滤组合框选择项 . 如果有不同的方式我们应该处理这个，请告诉我，但目前，我认为这可能是JDK中的一个错误？如果字段没有绑定，那么我们没有问题，但是一旦绑定，当字段失去焦点或按下回车键时会发生此异常 .

1 回答

我使用您的控件创建了一个快速示例：

@Override
public void start(Stage primaryStage) {

    AutoCompleteComboBox<CodeTableValue> myAutoCompleteBox = 
            new AutoCompleteComboBox<>();
    myAutoCompleteBox.setInitItems(FXCollections.observableArrayList(new CodeTableValue("One", "1"), 
            new CodeTableValue("Two", "2"), new CodeTableValue("Three", "4")));

    StackPane root = new StackPane(myAutoCompleteBox);
    myAutoCompleteBox.getSelectionModel().selectedItemProperty().addListener((obs, ov, nv) -> {
                    System.out.println(nv);
      });

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

基于一个简单的模型类：

public class CodeTableValue {

    private String code;
    private String value;

    public CodeTableValue(String code, String value) {
        this.code = code;
        this.value = value;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "code=" + code + ", value=" + value;
    }
}

完成输入后，我可以重现您的异常，然后单击Enter提交值并离开控件：

java.lang.ClassCastException: java.lang.String cannot be cast to CodeTableValue

异常来自以下事实：在编辑模式下从ComboBox使用的_1370426将始终返回 String ，但您强制自定义ComboBox使用 CodeTableValue 类 .

解决方案只是提供一种使用 StringConverter 在String和 CodeTableValue 之间进行转换的方法 .

所以我修改了你的控件：

public AutoCompleteComboBox(StringConverter<T> converter) {
    setEditable(true);
    setOnKeyReleased(e -> handleOnKeyReleasedEvent(e));
    setOnMouseClicked(e -> handleOnMouseClicked(e));

    super.setConverter(converter);
}

现在在样本中：

AutoCompleteComboBox<CodeTableValue> myAutoCompleteBox = 
            new AutoCompleteComboBox<>(new StringConverter<CodeTableValue>() {

        @Override
        public String toString(CodeTableValue object) {
            if (object != null) {
                return object.getValue();
            } 
            return null;
        }

        @Override
        public CodeTableValue fromString(String string) {
            return new CodeTableValue(string, string);
        }

    });

这现在有效，没有 ClassCastException .

显然，你必须提供一种键入字符串的方法（ code 或 value ）并从中检索另一个字符串 .

回复于 2024-04-25T22:44:25+08:00

JavaFX ComboBox的错误？

1 回答

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