javafx-2 - JavaFX 2 空白标签刷新问题

Question

我有一个每秒更新数百次的 Java FX 2 应用程序。我遇到了一个问题，标签在几分之一秒内部分空白，但这种情况经常发生。我该如何解决？

Answer 1

每秒调用数百次Platform.runLater()不是一个好主意。我建议您在调用 Platform.runLater() 以更新您的 UI 之前限制数据源的输入速度或将数据一起批处理，这样 Platform.runLater 的调用次数不会超过每秒 30 次。

我提交了一个 jira 请求RT-21569来改进 Platform.runLater 调用的文档，并考虑在底层平台中实现一个优越的 runLater 事件节流系统。

Richard Bair 在此论坛主题中提供了批处理 runLater 事件的示例解决方案。

import javafx.application.Application;
import javafx.application.Platform;
import javafx.scene.Scene;
import javafx.scene.control.ListView;
import javafx.stage.Stage;

import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.Semaphore;

/**
 *
 */
public class BackgroundLoadingApp extends Application {

    private ListView<String> listView;

    private List<String> pendingItems;

    private Semaphore lock = new Semaphore(1);

    protected void addItem(String item) throws InterruptedException {
        if (Platform.isFxApplicationThread()) {
            listView.getItems().add(item);
        } else {
            // It might be that the background thread
            // will update this title quite frequently, and we need
            // to throttle the updates so as not to completely clobber
            // the event dispatching system.
            lock.acquire();
            if (pendingItems == null) {
                pendingItems = new LinkedList<String>();
                pendingItems.add(item);
                Platform.runLater(new Runnable() {
                    @Override public void run() {
                        try {
                            lock.acquire();
                            listView.getItems().addAll(pendingItems);
                            pendingItems = null;
                        } catch (InterruptedException ex) {
                            ex.printStackTrace();
                        } finally {
                            lock.release();
                        }
                    }
                });
            } else {
                pendingItems.add(item);
            }
            lock.release();
        }
    }

    /**
     * The main entry point for all JavaFX applications.
     * The start method is called after the init method has returned,
     * and after the system is ready for the application to begin running.
     * <p/>
     * <p>
     * NOTE: This method is called on the JavaFX Application Thread.
     * </p>
     *
     * @param primaryStage the primary stage for this application, onto which
     *                     the application scene can be set. The primary stage will be embedded in
     *                     the browser if the application was launched as an applet.
     *                     Applications may create other stages, if needed, but they will not be
     *                     primary stages and will not be embedded in the browser.
     */
    @Override public void start(Stage primaryStage) throws Exception {
        listView = new ListView<String>();
        primaryStage.setScene(new Scene(listView));
        primaryStage.show();

        // Start some background thread to load millions of rows as fast as it can. But do
        // so responsibly so as not to throttle the event thread
        Thread th = new Thread() {
            @Override public void run() {
                try {
                    for (int i=0; i<2000000; i++) {
                        addItem("Item " + i);
                        if (i % 200 == 0) {
                            Thread.sleep(20);
                        }
                    }
                } catch (InterruptedException ex) {
                    ex.printStackTrace();
                }
            }
        };
        th.setDaemon(true);
        th.start();
    }

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

Richard Bair 的评论从引用的论坛帖子中复制：

这是一个模拟一些长时间运行的线程产生大量数据的示例。我发现它不太符合我的喜好。如果 Thread.sleep 丢失，它仍然会淹没进程（也许这是我在这种情况下处理并发的方式）。我还发现，如果我将它减少到“2”毫秒的睡眠时间，那么我就无法抓住滚动条拇指并移动它。我认为这里的问题是事件队列中有一个用于按下和拖动的鼠标事件，但是在拖动事件之间，新项目被添加到列表中，导致拇指移动，因为这比我的拖动事件更频繁地发生拇指永远不会去我想要的地方。我认为这是由于根据行数处理拇指位置的方式，