我想将 TableViewCell 中的 CheckBox 绑定(bind)到 BooleanBinding。以下示例由具有列 name
和 isEffectiveRequired
的 TableView 组成。列中的复选框绑定(bind)到表达式:
isRequired.or(name.isEqualTo("X"))
因此,当行中的项目是必需的或名称是 X 时,该项目是“有效必需的”,则表达式应该为 true。
不幸的是,复选框没有反射(reflect)更改。为了调试,我添加了一个文本字段,显示 nameProperty
、requiredProperty
和计算的 effectiveRequiredProperty
。
有趣的是,当仅返回 isRequiredProperty 而不是绑定(bind)时,复选框起作用。
public ObservableBooleanValue effectiveRequiredProperty() {
// Bindings with this work:
// return isRequired;
// with this not
return isRequired.or(name.isEqualTo(SPECIAL_STRING));
}
那么就 CheckBox 而言,Property 和 ObservableValue 之间有什么区别?
public class TableCellCBBinding extends Application {
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception {
init(primaryStage);
primaryStage.show();
}
private void init(Stage primaryStage) {
primaryStage.setScene(new Scene(buildContent()));
}
private Parent buildContent() {
TableView<ViewModel> tableView = new TableView<>();
tableView.setItems(sampleEntries());
tableView.setEditable(true);
tableView.getColumns().add(buildRequiredColumn());
tableView.getColumns().add(buildNameColumn());
// Add a Textfield to show the values for the first item
// As soon as the name is set to "X", the effectiveRequiredProperty should evaluate to true and the CheckBox should reflect this but it does not
TextField text = new TextField();
ViewModel firstItem = tableView.getItems().get(0);
text.textProperty()
.bind(Bindings.format("%s | %s | %s", firstItem.nameProperty(), firstItem.isRequiredProperty(), firstItem.effectiveRequiredProperty()));
return new HBox(text, tableView);
}
private TableColumn<ViewModel, String> buildNameColumn() {
TableColumn<ViewModel, String> nameColumn = new TableColumn<>("Name");
nameColumn.setCellValueFactory(new PropertyValueFactory<>("name"));
nameColumn.setCellFactory(TextFieldTableCell.forTableColumn());
nameColumn.setEditable(true);
return nameColumn;
}
private TableColumn<ViewModel, Boolean> buildRequiredColumn() {
TableColumn<ViewModel, Boolean> requiredColumn = new TableColumn<>("isEffectiveRequired");
requiredColumn.setMinWidth(50);
// This is should bind my BindingExpression from to ViewModel to the CheckBox
requiredColumn.setCellValueFactory( p -> p.getValue().effectiveRequiredProperty());
requiredColumn.setCellFactory( CheckBoxTableCell.forTableColumn(requiredColumn));
return requiredColumn;
}
private ObservableList<ViewModel> sampleEntries() {
return FXCollections.observableArrayList(
new ViewModel(false, "A"),
new ViewModel(true, "B"),
new ViewModel(false, "C"),
new ViewModel(true, "D"),
new ViewModel(false, "E"));
}
public static class ViewModel {
public static final String SPECIAL_STRING = "X";
private final StringProperty name;
private final BooleanProperty isRequired;
public ViewModel(boolean isRequired, String name) {
this.name = new SimpleStringProperty(this, "name", name);
this.isRequired = new SimpleBooleanProperty(this, "isRequired", isRequired);
this.name.addListener((observable, oldValue, newValue) -> System.out.println(newValue));
}
public StringProperty nameProperty() {return name;}
public final String getName(){return name.get();}
public final void setName(String value){
name.set(value);}
public boolean isRequired() {
return isRequired.get();
}
public BooleanProperty isRequiredProperty() {
return isRequired;
}
public void setRequired(final boolean required) {
this.isRequired.set(required);
}
public ObservableBooleanValue effectiveRequiredProperty() {
// Bindings with this work:
// return isRequired;
// with this not
return isRequired.or(name.isEqualTo(SPECIAL_STRING));
}
}
}
在名称中输入 X 时,应选中该行中的复选框。
在名称中输入 X 时,不会选中该行中的复选框。它从未被检查过,就像它根本没有绑定(bind)一样。
最佳答案
CheckBoxXXCells 在绑定(bind)其选定状态时不符合其文档,例如(这里引用只是为了签名,即使没有明确设置):
public final Callback
<Integer,ObservableValue<Boolean>>
getSelectedStateCallback()Returns the Callback that is bound to by the CheckBox shown on screen.
清楚地讨论了 ObservableValue,因此我们期望它至少显示选择状态。
实际上,如果它不是属性(其 updateItem 中的相关部分),则实现不会执行任何操作:
StringConverter<T> c = getConverter();
if (showLabel) {
setText(c.toString(item));
}
setGraphic(checkBox);
if (booleanProperty instanceof BooleanProperty) {
checkBox.selectedProperty().unbindBidirectional((BooleanProperty)booleanProperty);
}
ObservableValue<?> obsValue = getSelectedProperty();
if (obsValue instanceof BooleanProperty) {
booleanProperty = (ObservableValue<Boolean>) obsValue;
checkBox.selectedProperty().bindBidirectional((BooleanProperty)booleanProperty);
}
checkBox.disableProperty().bind(Bindings.not(
getTableView().editableProperty().and(
getTableColumn().editableProperty()).and(
editableProperty())
));
要解决此问题,请使用自定义单元格来更新其 updateItem 中的选定状态。由于增加了一个怪癖,我们需要禁用检查的触发,以真正保持视觉效果与支持状态同步:
requiredColumn.setCellFactory(cc -> {
TableCell<ViewModel, Boolean> cell = new TableCell<>() {
CheckBox check = new CheckBox() {
@Override
public void fire() {
// do nothing - visualizing read-only property
// could do better, like actually changing the table's
// selection
}
};
{
getStyleClass().add("check-box-table-cell");
check.setOnAction(e -> {
e.consume();
});
}
@Override
protected void updateItem(Boolean item, boolean empty) {
super.updateItem(item, empty);
if (empty || item == null) {
setText(null);
setGraphic(null);
} else {
check.setSelected(item);
setGraphic(check);
}
}
};
return cell;
});
关于javafx - 将 CheckBoxTableCell 绑定(bind)到 BooleanBinding,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60523457/