java - 连接具有 StringConverter 的 slider 和微调器

Question

对于数字输入，有时将模拟控件同步到文本显示会很方便。在这个 Swing 中example ，一个 JSpinner 和一个 JSlider 各自监听变化事件，并且各自更新对方的模型以匹配。一个类似的 JavaFX 程序，如下所示，连接一个 Spinner和一个 Slider ，并且这些听众保持控件的协调:

slider.valueProperty().addListener((Observable o) -> {
    spinner.getValueFactory().setValue(slider.getValue());
});
spinner.valueProperty().addListener((Observable o) -> {
    slider.setValue((double) spinner.getValue());
});

不幸的是，当我将 StringConverter 添加到微调器的 SpinnerValueFactory 时，初始值是未格式化的，直到任一控件发生更改 — 即使再次显式设置初始值，< em>在 添加转换器之后:

spinner.getValueFactory().setConverter(…);
spinner.getValueFactory().setValue(INITIAL_VALUE);

我哪里错了？

import java.text.NumberFormat;
import javafx.application.Application;
import javafx.beans.Observable;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Slider;
import javafx.scene.control.Spinner;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import javafx.util.converter.PercentageStringConverter;

/**
 * @see https://stackoverflow.com/a/6067986/230513
 */
public class SpinSlider extends Application {

    private static final double MIN = 0;
    private static final double MAX = 1;
    private static final double INITIAL_VALUE = 0.5;
    private static final double STEP_INCREMENT = 0.1;

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("SpinSlider");
        Slider slider = new Slider(MIN, MAX, INITIAL_VALUE);
        slider.setBlockIncrement(STEP_INCREMENT);
        Spinner spinner = new Spinner(MIN, MAX, INITIAL_VALUE, STEP_INCREMENT);
        spinner.getValueFactory().setConverter(
            new PercentageStringConverter(NumberFormat.getPercentInstance()));
        spinner.getValueFactory().setValue(INITIAL_VALUE);
        slider.valueProperty().addListener((Observable o) -> {
            spinner.getValueFactory().setValue(slider.getValue());
        });
        spinner.valueProperty().addListener((Observable o) -> {
            slider.setValue((double) spinner.getValue());
        });
        GridPane root = new GridPane();
        root.addRow(0, slider, spinner);
        root.setPadding(new Insets(8, 8, 8, 8));
        root.setHgap(8);
        Scene scene = new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }

}

Answer 1

您的 INITIAL_VALUE 首先用作微调器构造函数的 initialValue 参数。在内部，旋转器的混凝土 SpinnerValueFactory是一个 DoubleSpinnerValueFactory，它将 ChangeListener 添加到它的 value 属性；当再次设置初始值时，该值并没有真正改变。有两种方法:

1. 为构造函数指定一个不同的值，并在添加转换器后设置所需的值:

   Spinner spinner = new Spinner(MIN, MAX, -42, STEP_INCREMENT);
   spinner.getValueFactory().setConverter(…);
   spinner.getValueFactory().setValue(INITIAL_VALUE);
   

2. 构造一个具有所需初始值的 SpinnerValueFactory 并使用它来构造微调器:

   SpinnerValueFactory factory = new SpinnerValueFactory
       .DoubleSpinnerValueFactory(MIN, MAX, INITIAL_VALUE, STEP_INCREMENT);
   factory.setConverter(…);
   Spinner spinner = new Spinner(factory);
   

此外，下面的示例将两个监听器替换为双向绑定(bind)，它使用弱监听器来允许对属性进行垃圾回收:

slider.valueProperty().bindBidirectional(
    spinner.getValueFactory().valueProperty());

简单地说，微调器和 slider 可以相互控制。更常见的是，每个模型都可以在控制另一个模型持有的属性的过程中保持同步:

model.xProperty().bindBidirectional(slider.valueProperty());
model.xProperty().bindBidirectional(spinner.getValueFactory().valueProperty());

import java.text.NumberFormat;
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Slider;
import javafx.scene.control.Spinner;
import javafx.scene.control.SpinnerValueFactory;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import javafx.util.converter.PercentageStringConverter;

/**
 * @see https://stackoverflow.com/a/55427307/230513
 * @see https://stackoverflow.com/a/6067986/230513
 */
public class SpinSlider extends Application {

    private static final double MIN = 0;
    private static final double MAX = 1;
    private static final double INITIAL_VALUE = 0.5;
    private static final double STEP_INCREMENT = 0.1;

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("SpinSlider");
        Slider slider = new Slider(MIN, MAX, INITIAL_VALUE);
        slider.setBlockIncrement(STEP_INCREMENT);
        SpinnerValueFactory factory = new SpinnerValueFactory
            .DoubleSpinnerValueFactory(MIN, MAX, INITIAL_VALUE, STEP_INCREMENT);
        factory.setConverter(new PercentageStringConverter(
            NumberFormat.getPercentInstance()));
        Spinner spinner = new Spinner(factory);
        slider.valueProperty().bindBidirectional(spinner.getValueFactory().valueProperty());
        GridPane root = new GridPane();
        root.addRow(0, slider, spinner);
        root.setPadding(new Insets(8, 8, 8, 8));
        root.setHgap(8);
        Scene scene = new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }

}