Question

当我使用JavaFX时，睡眠功能将无法正常工作。像下面的代码一样：

public class Controller {

@FXML private Label label;
@FXML private Button b1;

public void write() throws InterruptedException
{
    label.setText("FIRST TIME");
    for(int i=1;i<=5;i++)
    {
        System.out.println("Value "+i);
        label.setText("Value "+i);
        Thread.sleep(2000);
    }
    label.setText("LAST TIME");
}

按下按钮b1时，将调用写入功能。现在，在控制台上2秒钟后将打印“ Value + i”。但是那个时候标签l1的文本没有改变，最后只变成了“ LAST TIME”。这里有什么问题？

Answer 1

在阅读了注释中建议的链接之后，您可能希望从fx线程中删除较长的过程（延迟）。
您可以通过调用另一个线程来实现：

public void write() {

    label.setText("FIRST TIME");

    new Thread(()->{ //use another thread so long process does not block gui
        for(int i=1;i<=6;i++)   {
            String text;
            if(i == 6 ){
                text = "LAST TIME";
            }else{
                 final int j = i;
                 text = "Value "+j;
            }

            //update gui using fx thread
            Platform.runLater(() -> label.setText(text));
            try {Thread.sleep(2000);} catch (InterruptedException ex) { ex.printStackTrace();}
        }

    }).start();
}

或者更好地使用fx动画工具，例如：

private int i = 0; // a filed used for counting 

public void write() {

    label.setText("FIRST TIME");

    PauseTransition pause = new PauseTransition(Duration.seconds(2));
    pause.setOnFinished(event ->{
        label.setText("Value "+i++);
        if (i<=6) {
            pause.play();
        } else {
            label.setText("LAST TIME");
        }
    });
    pause.play();
}

Answer 2

我会尝试创建用于延迟的新线程。

package sample;

import javafx.application.Platform;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;

public class Controller implements Runnable{


    private volatile boolean isRunning = false;
    private Thread timer;

    private int delay = 2000;

    @FXML
    private Label label;

    @FXML
    private Button button;


    private void start(){
        timer = new Thread(this, "timer");
        isRunning = true;
        timer.start();
    }

    private void stop(){
        isRunning = false;
    }

    private void interrupt(){
        isRunning = false;
        timer.interrupt();
    }

    @Override
    public void run() {
        int counter = 0;
        while (isRunning) {
            try {
                ++counter;
                String text = "MyText" + counter;
                Platform.runLater(() -> label.setText(text));

                if (counter == 5) {
                    stop();
                }


                Thread.currentThread().sleep(delay);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    }
}

更新Platform.runLater()下的标签非常重要-JavaFx主线程是唯一允许更新JavaFx对象的线程。

为什么Thread.sleep（）在JavaFX中无法正常工作？

2 个答案: