JavaFX进度指示符更新不正确

Question

我正在创建一个JavaFX桌面应用程序，我在上面模拟一些工作负载。我希望应用程序有一个动态更新的进度指示器（随着时间的推移），以显示加载过程是如何进行的。这是我的应用程序类：

public class App extends Application {

@Override
public void init() throws InterruptedException{
    //Simulation of time consuming code.
    for(int i = 0; i<=10; i++) {
        notifyPreloader(new Preloader.ProgressNotification(i/10));
        System.out.println("Progress is being set by the app to: " + (i/10));
        Thread.sleep(500);
    }
}

@Override
public void start(Stage primaryStage) {
    Parent root;
    try {
        root = FXMLLoader.load(getClass().getResource("/gui/fxml/App.fxml"));
        Scene scene = new Scene(root, 600, 400);

        scene.getStylesheets().add("/gui/style/app.css");

        primaryStage.setScene(scene);
        primaryStage.setTitle("Hello World!");
        primaryStage.show();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

这是我的预加载程序类：

public class AppPreloader extends Preloader {
private Stage preloaderStage;
private Parent root;
private Scene scene;
private ProgressIndicator progress_indicator;

@Override
public void start(Stage primaryStage) throws Exception {
    this.preloaderStage = primaryStage;
    this.preloaderStage.setScene(this.scene);
    this.preloaderStage.show();
    this.progress_indicator = (ProgressIndicator) scene.lookup("#progressIndicator");
}


@Override
public void init() throws Exception {
    root = FXMLLoader.load(getClass().getResource("/gui/fxml/AppPreloader.fxml"));
    Platform.runLater(new Runnable() { 
        @Override
        public void run() {
            scene = new Scene(root, 600, 400);
            scene.getStylesheets().add("/gui/style/appPreloader.css");
        }
    });
}

@Override
public void handleProgressNotification(ProgressNotification pn) {
    if(pn instanceof ProgressNotification){
        progress_indicator.setProgress(pn.getProgress());
        System.out.println("Progress is being set by the handle method to: " + pn.getProgress());
    }
}

@Override
public void handleStateChangeNotification(StateChangeNotification evt) {
    if (evt.getType() == StateChangeNotification.Type.BEFORE_START) {
        preloaderStage.hide();
    }
}    
}

另外，我需要说的是，我已经检查了这两个问题（预加载程序中的progressbar不更新和javafx预加载程序不更新进度），但没有找到解决问题的方法。

非常感谢您抽出时间。

Answer 1

首先，您没有看到预期的进度值，因为您使用的是整数算术:i和10都是整数，所以i=10时i/10是0和1。

其次，HandleProgressNotification和HandleStateChangeNotification方法是与加载资源相关的应用程序生命周期的一部分。这些实际上是JavaFX仍然支持web部署的时候遗留下来的，现在可能用途有限。

要从应用程序接收通知，您需要重写HandleApplicationNotification(...)方法。以下是这两个类的更正版本（也被修改为独立的，以便它们可以复制和运行：请在您的问题中提供这些类型的示例）

package application;

import javafx.application.Application;
import javafx.application.Preloader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class App extends Application {

    @Override
    public void init() throws InterruptedException{
        //Simulation of time consuming code.
        for(int i = 0; i<=10; i++) {
            notifyPreloader(new Preloader.ProgressNotification(i/10.0));
            System.out.println("Progress is being set by the app to: " + (i/10.0));
            Thread.sleep(500);
        }
        notifyPreloader(new Preloader.StateChangeNotification(Preloader.StateChangeNotification.Type.BEFORE_START));
    }

    @Override
    public void start(Stage primaryStage) {
        Parent root;
            root = new StackPane(new Label("Hello World"));
            Scene scene = new Scene(root, 600, 400);

            primaryStage.setScene(scene);
            primaryStage.setTitle("Hello World!");
            primaryStage.show();

    }

}

package application;

import javafx.application.Preloader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.ProgressIndicator;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class AppPreloader extends Preloader {
    private Stage preloaderStage;
    private Parent root;
    private Scene scene;
    private ProgressIndicator progress_indicator;

    @Override
    public void start(Stage primaryStage) throws Exception {
        progress_indicator = new ProgressIndicator();
        root = new StackPane(progress_indicator);
        scene = new Scene(root, 600, 400);
        this.preloaderStage = primaryStage;
        this.preloaderStage.setScene(this.scene);
        this.preloaderStage.show();
    }


    @Override
    public void handleApplicationNotification(PreloaderNotification pn) {
        if (pn instanceof ProgressNotification) {
           //expect application to send us progress notifications 
           //with progress ranging from 0 to 1.0
           double v = ((ProgressNotification) pn).getProgress();
           progress_indicator.setProgress(v);            
        } else if (pn instanceof StateChangeNotification) {
            StateChangeNotification scn = (StateChangeNotification) pn ;
            if (scn.getType() == StateChangeNotification.Type.BEFORE_START) {
                preloaderStage.hide();
            }
        }
    } 
}