本文介绍了从JavaFX中从Task API调用的嵌套函数更新标签的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我正在使用此类执行一些后台任务

 类下载扩展任务{
protected Object call()抛出异常{
try {
updateMessage(建立连接);
DownloadHelper downloadHelper = new DownloadHelper();
downloadHelper.performTask();
返回null;
} catch(IOException | ParseException ex){
logger.error(ExceptionUtils.getStackTrace(ex));
抛出前;
}
}
}

此任务依次调用DownloadHelper执行某项任务。

  class DownloadHelper {
public DownloadHelper(){
}

public void performTask(){
----
----
}
}

有没有办法从DownloadHelper类更新Task API(updateMessage())的状态消息。?

解决方案

权宜之计是将下载任务的引用作为参数传递给 DownloadHelper 构造函数。为了最小化耦合,您可以将 updateMessage()的实现引用传递为类型

  import java.util.function.Consumer; 
import javafx.application.Application;
import javafx.beans.InvalidationListener;
import javafx.beans.Observable;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

/ **
* @see https://stackoverflow.com/q/45708923/230513
* /
公共类MessageTest扩展应用程序{

@Override
public void start(Stage primaryStage){
primaryStage.setTitle(MessageTest);
StackPane root = new StackPane();
Label label = new Label();
root.getChildren()。add(label);
场景场景=新场景(root,320,120);
primaryStage.setScene(scene);
primaryStage.show();
下载任务=新下载();
task.messageProperty()。addListener((Observable o) - > {
label.setText(task.getMessage());
});
Thread thread = new Thread(task);
thread.setDaemon(true);
thread.start();
}

私有静态类下载扩展任务< String> {

@Override
protected String call()抛出异常{
updateMessage(建立连接);
DownloadHelper helper = new DownloadHelper(this :: updateMessage);
helper.performTask();
返回MessageTest;
}

@Override
protected void updateMessage(String message){
super.updateMessage(message);
}
}

私有静态类DownloadHelper {

Consumer< String>更新;

public DownloadHelper(Consumer< String> updater){
this.updater = updater;
}

public void performTask(){
updater.accept(Helper message);
}
}

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

}


I am performing some background task using this class

class Download extends Task{
     protected Object call() throws Exception {
        try {
            updateMessage("Establishing Connection");
            DownloadHelper downloadHelper = new DownloadHelper();
            downloadHelper.performTask();
            return null;
        } catch (IOException | ParseException ex) {
            logger.error(ExceptionUtils.getStackTrace(ex));
            throw ex;
        }
    }
}

This Task in turn calls DownloadHelper to perform some task.

class DownloadHelper{
    public DownloadHelper(){
    }

    public void performTask(){
    ----
    ----
    }
}

Is there a way to update the status message of the Task API (updateMessage()) from the DownloadHelper class.?

解决方案

The expedient approach is to pass a reference to the Download task as a parameter to the DownloadHelper constructor. To minimize coupling, you can instead pass a reference to your implementation of updateMessage() as a parameter of type Consumer, "an operation that accepts a single input argument and returns no result."

DownloadHelper helper = new DownloadHelper(this::updateMessage);

Your helper's implementation of performTask() can then ask the updater to accept() messages as needed.

Consumer<String> updater;

public DownloadHelper(Consumer<String> updater) {
    this.updater = updater;
}

public void performTask() {
    updater.accept("Helper message");
}

A related example is seen here.

import java.util.function.Consumer;
import javafx.application.Application;
import javafx.beans.InvalidationListener;
import javafx.beans.Observable;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

/**
 * @see https://stackoverflow.com/q/45708923/230513
 */
public class MessageTest extends Application {

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("MessageTest");
        StackPane root = new StackPane();
        Label label = new Label();
        root.getChildren().add(label);
        Scene scene = new Scene(root, 320, 120);
        primaryStage.setScene(scene);
        primaryStage.show();
        Download task = new Download();
        task.messageProperty().addListener((Observable o) -> {
            label.setText(task.getMessage());
        });
        Thread thread = new Thread(task);
        thread.setDaemon(true);
        thread.start();
    }

    private static class Download extends Task<String> {

        @Override
        protected String call() throws Exception {
            updateMessage("Establishing connection");
            DownloadHelper helper = new DownloadHelper(this::updateMessage);
            helper.performTask();
            return "MessageTest";
        }

        @Override
        protected void updateMessage(String message) {
            super.updateMessage(message);
        }
    }

    private static class DownloadHelper {

        Consumer<String> updater;

        public DownloadHelper(Consumer<String> updater) {
            this.updater = updater;
        }

        public void performTask() {
            updater.accept("Helper message");
        }
    }

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

}

这篇关于从JavaFX中从Task API调用的嵌套函数更新标签的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!

08-18 11:57