JavaFX 简单更新标签（线程）

Question

我正在尝试向一些初学者程序员演示如何在 JavaFX 应用程序上设置标签以自动更新。基本上，他们希望标签上的值每分钟减少一次，而无需任何用户交互。

Java 不是我的强项，通过查看以前的一些问题，我发现我需要处理线程和 Runnable()。

我已经将下面的代码放在一起，但我只是想知道是否有更好的方法来做到这一点或更简单的方法来用更简单的代码演示相同的结果。

public class MainTimer2 extends Application {
    private int count = 100;
    private Label response = new Label(Integer.toString(count));

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

    //Update function
    private void decrementCount() {
        count--;
        response.setText(Integer.toString(count));
    }

    @Override
    public void start(Stage myStage) {
        myStage.setTitle("Update Demo");

        //Vertical and horizontal gaps set to 10px
        FlowPane rootNode = new FlowPane(10, 10);

        rootNode.setAlignment(Pos.CENTER);

        Scene myScene = new Scene(rootNode, 200, 100);

        myStage.setScene(myScene);

        Thread thread = new Thread(new Runnable() {

            @Override
            public void run() {
                Runnable updater = new Runnable() {

                    @Override
                    public void run() {
                        decrementCount();
                    }
                };
                while (true) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException ex) {
                        System.out.println("Timer error");
                    }
                    // UI update is run on the Application thread
                    Platform.runLater(updater);
                }
            }
        });
        // don't let thread prevent JVM shutdown
        thread.setDaemon(true);
        thread.start();
        rootNode.getChildren().addAll(response);
        myStage.show();
    }
}

Answer 1

使用PauseTransition倒计时：

import javafx.animation.PauseTransition;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.FlowPane;
import javafx.stage.Stage;
import javafx.util.Duration;

public class MainTimer2 extends Application {

    private int count = 100;
    private Label response = new Label(Integer.toString(count));

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

    @Override
    public void start(Stage myStage) {
        myStage.setTitle("Update Demo");

        //Vertical and horizontal gaps set to 10px
        FlowPane rootNode = new FlowPane(10, 10);
        rootNode.setAlignment(Pos.CENTER);

        Scene myScene = new Scene(rootNode, 200, 100);
        myStage.setScene(myScene);

        rootNode.getChildren().addAll(response);
        myStage.show();
        update();
    }

    private void update() {

        PauseTransition pause = new PauseTransition(Duration.seconds(1));
        pause.setOnFinished(event ->{
            decrementCount();
            pause.play();
        });
        pause.play();
    }

    //Update function
    private void decrementCount() {
        count = (count > 0) ? count -1 : 100;
        response.setText(Integer.toString(count));
    }
}

您也可以使用Timeline:

    private void update() {

        KeyFrame keyFrame = new KeyFrame(
                Duration.seconds(1),
                event -> {
                    decrementCount();
                }
        );
        Timeline timeline = new Timeline();
        timeline.setCycleCount(Animation.INDEFINITE);
        //if you want to limit the number of cycles use 
        //timeline.setCycleCount(100);
        timeline.getKeyFrames().add(keyFrame);
        timeline.play();
    }