Question

对于数字输入，将模拟控件与文本显示同步有时会很方便。在此Swing example中，JSpinner和JSlider分别监听更改事件，并分别更新对方的模型以进行匹配。如下所示，一个类似的JavaFX程序将Spinner和Slider连接起来，这些侦听器使控件保持协调：

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

不幸的是，当我在微调器的StringConverter中添加SpinnerValueFactory时，初始值未格式化，直到更改了任何一个控件为止-即使在之后添加转换器：

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

我要去哪里错了？

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首先用作微调器的构造函数的initialValue参数。在内部，微调框的具体SpinnerValueFactory是DoubleSpinnerValueFactory，它为其ChangeListener属性添加了value；当再次设置初始值时，该值实际上并没有更改。有两种方法可以证明自己：

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);

使用所需的初始值构造SpinnerValueFactory并将其用于构造微调器：

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

此外，下面的示例将两个侦听器替换为双向绑定，该双向绑定使用弱侦听器允许垃圾回收属性：

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

通常，微调器和滑块可以相互控制。更常见的是，每个人在控制其他模型拥有的财产的过程中可以保持同步：

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);
    }

}

连接具有StringConverter的滑块和微调器

1 个答案: