JavaFX -控制与并发

Question

我有一个示例Hello。我正在使用Eclipse和eFxclipse插件。我的Eclipse是开普勒，它是Eclipse4.3.2版本，是Jdk1.7-045。

我试图添加的是非常少的并发代码，我只想更新示例中的按钮文本。这个后端任务能否与前端UI控件交互，例如按钮、场景？如果不是，我如何进行定制的后端任务，然后与UI控件交互？

提前感谢

package com.juhani.fx.exer;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import javafx.application.Application;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;


public class HelloWorld extends Application{

    private static final short COREPOOLSIZE=2;
    private static final short MAXIMUMPOOLSIZE=2; 
    private static final int WORKQUEUECAPACITY=100;
    private static Logger log = LogManager.getLogger(
            HelloWorld.class.getName());

    private ExecutorService executors = new             ThreadPoolExecutor(COREPOOLSIZE,MAXIMUMPOOLSIZE,20,TimeUnit.MINUTES,new ArrayBlockingQueue<Runnable>(WORKQUEUECAPACITY));



    public static void main(String[] args) {
       LogMessage logMessage = new LogMessage("BEGIN",1.0,1,"HELLOWORLD");
       log.trace(logMessage.toString());
       launch(args);        

   }

   @Override
   public void start(final Stage primaryStage) throws InterruptedException {
      primaryStage.setTitle("Hello World!");
      final Button btn = new Button();
      btn.setText("Say 'Hello World'");
      btn.setOnAction(new EventHandler<ActionEvent>() {
          @Override
          public void handle(ActionEvent event) {
            System.out.println("Hello World!");
         }
       });

      final StackPane root = new StackPane();
      root.getChildren().add(btn);
      final Scene scene= new Scene(root,300,250);
      primaryStage.setScene(scene);
      primaryStage.show();

      Task<Boolean> task = new Task<Boolean>() {
         @Override 
         public Boolean call() {    
            for(int i=0;i<20;i++){
               btn.setText("First row\nSecond row "+i);
               primaryStage.show();
               try {
                  Thread.sleep(1000);
               } catch (InterruptedException e) {
                  log.error(new LogMessage("entering interruption",1.0,2,"exception").toString());                       
               }
            }
            return new Boolean(true);               
          }        
       };           
       executors.submit(task);      
    }   
}

Answer 1

这个答案特别提到了Platform.runLater的使用。如果您使用的是任务，最好使用它提供的方法更新UI，如https://stackoverflow.com/a/24991703/1759128中所述。

要更新UI，您必须在Javafx线程上。

一旦您在任何其他线程上，使用Platform.runLater()将这些数据更新回Javafx。下面可以找到一个有用的示例

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;


public class HelloWorld extends Application {

    private static final short COREPOOLSIZE = 2;
    private static final short MAXIMUMPOOLSIZE = 2; 
    private static final int WORKQUEUECAPACITY = 100;

    private ExecutorService executors = new 
       ThreadPoolExecutor(COREPOOLSIZE, MAXIMUMPOOLSIZE, 20, TimeUnit.MINUTES,
                          new ArrayBlockingQueue<Runnable>(WORKQUEUECAPACITY));

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

    @Override
    public void start(final Stage primaryStage) throws InterruptedException {
        primaryStage.setTitle("Hello World!");
        final Button btn = new Button();
        btn.setText("Say 'Hello World'");
        btn.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                System.out.println("Hello World!");
            }
        });

        final StackPane root = new StackPane();
        root.getChildren().add(btn);
        final Scene scene = new Scene(root, 300, 250);
        primaryStage.setScene(scene);
        primaryStage.show();

        Task<Boolean> task = new Task<Boolean>() {
            @Override 
            public Boolean call() {    
                final AtomicInteger i = new AtomicInteger(0);
                for( ; i.get() < 20; i.incrementAndGet()) {
                    Platform.runLater(new Runnable() {
                        @Override
                        public void run() {
                            btn.setText("First row\nSecond row " + i);                      
                        }
                    });

                try {
                  Thread.sleep(1000);
                }
                catch (InterruptedException e) {}
            }
            return Boolean.valueOf(true);               
          }        
       };           
       executors.submit(task);      
    }   
}

有关更多信息，您可以查看提供的here链接

Answer 2

任务是用来与fx应用程序线程上的ui交互的，为了利用这种支持，您应该使用它的设计:-)

作为一般规则，您不能访问任务的call方法*中的ui。相反，更新它的一个属性(消息、进度.)并将该属性绑定到您的ui中。样本代码：

Task<Boolean> taskWithBinding = new Task<Boolean>() {
    @Override 
    public Boolean call() {    
        final AtomicInteger i = new AtomicInteger(0);
        for( ; i.get() < 20; i.incrementAndGet()) {
            updateMessage("First row\nSecond row " + i);                      
            try {
                Thread.sleep(1000);
            }
            catch (InterruptedException e) {
                return Boolean.FALSE;
            }
        }
        return Boolean.TRUE;               
    }        
};           
btn.textProperty().bind(taskWithBinding.messageProperty());

*在runLater中概述了一个异常(将访问包装到other answer中)。这样做在技术上是正确的，但随后您将传递任务的能力，并且可以使用任意运行的.