JavaFXでStopWatch

StopWatch.md

package jp.example;

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.*;
import javafx.geometry.Pos;
import javafx.scene.control.Label;
import javafx.scene.control.ToggleButton;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.scene.Scene;
import javafx.util.Duration;

public class Main extends Application {

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

    private final StopWatch stopWatch = new StopWatch();
    private final Label elapsed_Label = new Label();

    @Override
    public void start(final Stage primaryStage) {
        elapsed_Label.textProperty().bind(stopWatch.timeProperty().asString());
        elapsed_Label.setStyle("-fx-font-size: 6em; -fx-text-fill: RED;");

        final ToggleButton button = new ToggleButton();
        button.textProperty().bind(Bindings.when(button.selectedProperty()).then("Stop").otherwise("Start"));
        button.setOnAction(event -> {
            final ToggleButton source = (ToggleButton) event.getSource();
            if (source.isSelected()) {
                stopWatch.play();
            } else {
                stopWatch.stop();
            }
        });

        final VBox vbox = new VBox(20);
        vbox.setAlignment(Pos.CENTER);
        vbox.getChildren().addAll(button, elapsed_Label);
        final Scene scene = new Scene(vbox, 400, 320);
        primaryStage.setTitle("ストップウォッチ");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}

class StopWatch {
    private final Timeline timeline;
    private final Duration START_TIME = Duration.ZERO;
    private final ReadOnlyObjectWrapper<Duration> elapsed = new ReadOnlyObjectWrapper<>(START_TIME);

    StopWatch() {
        timeline = new Timeline(new KeyFrame(Duration.millis(10), event -> {
            final Duration duration = ((KeyFrame) event.getSource()).getTime();
            elapsed.set(elapsed.get().add(duration));
        }));
        timeline.setCycleCount(Timeline.INDEFINITE);
    }

    public ReadOnlyObjectWrapper<Duration> timeProperty() {
        return elapsed;
    }

    public void play() {
        elapsed.set(START_TIME);
        timeline.play();
    }

    public void stop() {
        timeline.stop();
    }
}