Javafx 中的 ProgressBar 不会在 onAction 块中更新 [英] ProgressBar in Javafx does not update in onAction block

问题描述

我想要一个在 onAction 块内更新的进度条.由于某些原因，在以下代码中，进度条在退出 onAction 块之前不会更新.我在 9 秒内没有任何进展，然后是 90%.System.out 打印得很好.

I'd like to have a progress bar that updates inside an onAction block. For some reason in the following code, the progress bar doesn't update until it exits the onAction block. I get no progress for nine seconds and then 90%. The System.out prints just fine.

package net.snortum.play;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class ProgressBarTester extends Application {

    public static void main( String[] args ) {
        launch( ProgressBarTester.class, args );
    }

    @Override
    public void start( final Stage stage ) throws Exception {
        final GridPane grid = new GridPane();
        grid.setAlignment( Pos.CENTER );
        grid.setHgap( 10 );
        grid.setVgap( 10 );
        grid.setPadding( new Insets( 25, 25, 25, 25 ) );

        final Text title = new Text( "Test Progress Bar" );
        int col = 0, row = 0, colSpan = 2, rowSpan = 1;
        grid.add( title, col, row, colSpan, rowSpan );

        col = 0; 
        row++;
        grid.add( new Label( "Progress:" ), col, row );
        col = 1; 
        final ProgressBar progress = new ProgressBar( 0.0 );
        grid.add( progress, col, row );

        final HBox hbox = new HBox();
        hbox.setAlignment( Pos.BASELINE_RIGHT );
        final Button submit = new Button( "Go" );
        hbox.getChildren().add( submit );
        col = 1; 
        row++;
        grid.add( hbox, col, row );

        submit.setOnAction( new EventHandler<ActionEvent>() {

            @Override
            public void handle( ActionEvent event ) {
                double size = 10.0;
                for (double i = 0.0; i < size; i++){
                    progress.setProgress( i / size );
                    System.out.printf("Complete: %02.2f%n", i * 10);

                    try {
                        Thread.sleep(1000); 
                    } catch(InterruptedException ex) {
                        Thread.currentThread().interrupt();
                    }
                }
            }

        } );

        final Scene scene = new Scene( grid );
        stage.setScene( scene );
        stage.setTitle( "Test Progress Bar" );
        stage.show();
    }

}

推荐答案

tomsomtom 精确答案的长格式:

Long form of tomsomtom's precise answer:

如果你使用 JavaFX 线程来做这种长期工作，你会停止 UI 更新等.所以你必须在一个单独的线程中运行你的工作线程.如果您在单独的线程中运行，则必须使用 runLater() 将所有 GUI 操作(如 progress.setProgress())传递回 JavaFX 线程，因为 JavaFX 不是多线程的.

If you use the JavaFX Thread to do this kind of long term work, you stop the UI from updating etc. So you have to run your worker in a sparate thread. If you run in a separate Thread, all GUI operatione like progress.setProgress() have to be passed back to the JavaFX Thread using runLater() as JavaFX is not multithreaded.

在你的操作中试试这个:

Try this in your Action:

    submit.setOnAction( new EventHandler<ActionEvent>() {
        @Override
        public void handle( ActionEvent event ) {
            double size = 10.0;
            new Thread(){
                public void run() {
                    for (double i = 0.0; i < size; i++){
                        final double step = i;
                        Platform.runLater(() -> progress.setProgress( step / size ));
                        System.out.printf("Complete: %02.2f%n", i * 10);

                        try {
                            Thread.sleep(1000); 
                        } catch(InterruptedException ex) {
                            Thread.currentThread().interrupt();
                        }
                    }
                }
            }.start();
        }

    } );

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