java - 如何为 TableView 使用自定义 cellFactories

Question

如何轻松地将自定义(可重用)cellFactories 应用到 javafx.scene.control.TableCell; 或 javafx.scene.control.TableView;？

Answer 1

要应用自定义 CellFactories 来格式化单元格中显示的文本、颜色等，以下示例可能会有很好的帮助。

初始情况

假设您有一个 Bean/POJO Person:

public class Person {
    private double levelOfGrowth = 0;

    public Person() {};

    public Person(double levelOfGrowth) {
        this.levelOfGrowth = levelOfGrowth;
    };

    public double getLevelOfGrowth() {
        return levelOfGrowth;
    }
}

其中 levelOfGrowth 是一个人的成长已经完成多少的百分比值。

它可能设置在 0.00 到 1.00 之间。

我们还假设您已经在绑定(bind)到 Controller MainWindowController 的 FXML 中创建了 View 。您还设置列以显示 levelOfGrowth 到 id levelOfGrowthColumn

public class MainWindowController implements Initializable {
    @FXML
    public TableColumn levelOfGrowthColumn;

    /**
     * Initializes the controller class.
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        ObservableList<Person> persons = FXCollections.observableArrayList();

        persons.add(new Person(0));
        persons.add(new Person(0.5));
        persons.add(new Person(1));

        levelOfGrowthColumn.setCellValueFactory(new PropertyValueFactory<Person, Double>("levelOfGrowth"));

    }
}

意图

上例中的问题是 View 中显示的值类似于 0.5 而不是 50%。我们还可能希望将 100% 等值的颜色更改为绿色。

解决方案

我们需要的是一个(可重用的)类，它描述了如何在 View 中格式化/打印 double 值，并将该类与 levelOfGrowthColumn 连接起来。

“格式化程序”类

public class PercantageFormatCell extends TableCell<Object, Double> {

    public PercantageFormatCell() {
    }

    @Override
    protected void updateItem(Double item, boolean empty) {
        super.updateItem(item, empty);

        // If the row is not empty but the Double-value is null,
        // we will always display 0%
        if (!empty && null == item) {
            item = new Double(0.0d);
        }

        // Here we set the displayed text to anything we want without changing the
        // real value behind it. We could also have used switch case or anything you
        // like.
        setText(item == null ? "" : NumberFormat.getPercentInstance().format(item));

        // If the cell is selected, the text will always be white
        // (so that it can be read against the blue background),
        // if the value is 1 it will be green.
        if (item != null) {
            double value = item.doubleValue();
            if (isFocused() || isSelected() || isPressed()) {
                setTextFill(Color.WHITE);
            } else if (value < 1) {
                setTextFill(Color.BLACK);
            } else {
                setTextFill(Color.GREEN);
            }
        }
    }
}

在你的 Controller 中使用它

public class MainWindowController implements Initializable {
    @FXML
    public TableColumn levelOfGrowthColumn;

    /**
     * Initializes the controller class.
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        ObservableList<Person> persons = FXCollections.observableArrayList();

        persons.add(new Person(0));
        persons.add(new Person(0.5));
        persons.add(new Person(1));

        // New code START

        // In case we have multiple columns with percent-values it
        // might come in handy to store our formatter
        Callback<TableColumn, TableCell> percantageCellFactory =
            new Callback<TableColumn, TableCell>() {
                public TableCell call(TableColumn p) {
                    return new PercantageFormatCell();
                }
            };

        // Now all we have to do is to apply it
        levelOfGrowthColumn.setCellFactory(percantageCellFactory);

        // New code END

        levelOfGrowthColumn.setCellValueFactory(new PropertyValueFactory<Person, Double>("levelOfGrowth"));

    }
}