使用时间轴并显示为标签的 JavaFX 倒计时

问题描述

我需要以 hh:mm:ss 格式创建一个倒计时，该格式每秒更新一次，并通过使用标签将其显示给用户，但我不确定如何执行此操作。当时间线为零时，也应采取行动。

解决方法

以下是使用 TimeLine 进行倒计时的一个示例：

package org.example;

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Label;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;
import javafx.util.Duration;

import java.time.temporal.ChronoUnit;

public class CountDownExampleApp extends Application {

    @Override
    public void start(Stage stage) {

        // Create label to display the time left:
        Label countDownLabel = new Label();

        // Create duration property for time remaining:
        ObjectProperty<java.time.Duration> remainingDuration
                = new SimpleObjectProperty<>(java.time.Duration.ofSeconds(5)); // Here: 5 sec count down

        // Binding with media time format (hh:mm:ss):
        countDownLabel.textProperty().bind(Bindings.createStringBinding(() ->
                        String.format("%02d:%02d:%02d",remainingDuration.get().toHours(),remainingDuration.get().toMinutesPart(),remainingDuration.get().toSecondsPart()),remainingDuration));

        // Create time line to lower remaining duration every second:
        Timeline countDownTimeLine = new Timeline(new KeyFrame(Duration.seconds(1),(ActionEvent event) ->
                remainingDuration.setValue(remainingDuration.get().minus(1,ChronoUnit.SECONDS))));

        // Set number of cycles (remaining duration in seconds):
        countDownTimeLine.setCycleCount((int) remainingDuration.get().getSeconds());

        // Show alert when time is up:
        countDownTimeLine.setOnFinished(event -> new Alert(Alert.AlertType.INFORMATION).show());

        // Prepare and show stage:
        stage.setScene(new Scene(new Pane(countDownLabel),200,100));
        stage.show();

        // Start the time line:
        countDownTimeLine.play();
    }

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