javafx并发性-使用一个在线程中运行但挂起UI的任务

在并发性方面有很多问题和答案,我的问题和答案可能与其他问题类似,但对于我来说,这不是重复的,因为某些原因,我必须错过一些东西,并希望得到一些建议…

我的问题更多的是,我需要第二双眼睛来指出我做的错误,以使我的代码能够在后台线程中运行,同时也更新了GUI,而不冻结它。

最初,使用线程中的任务将PDF文件上载到应用程序。

这个很好用。

将显示一个进度条,该进度条将无问题地设置动画:

上传文件()

public void uploadFile(File fileToProcess) {

  fileBeingProcessed = fileToProcess;

  Task<Parent> uploadingFileTask = new Task<Parent>() {
    @Override
    public Parent call() {
      try {
        progressBarStackPane.setVisible(true);
        pdfPath = loadPDF(fileBeingProcessed.getAbsolutePath());
        createPDFViewer();
        openDocument();
      } catch (IOException ex) {
        java.util.logging.Logger.getLogger(MainSceneController.class.getName()).log(Level.SEVERE, null, ex);
      }
      return null;
    }
  };

  uploadingFileTask.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
    @Override
    public void handle(WorkerStateEvent event) {
      fileHasBeenUploaded = true;
      progressBarStackPane.setVisible(false);
      uploadFilePane.setVisible(false);
      tabPane.setVisible(true);

      /* This is where I am getting issue, more so in createThumbnailPanels() */

      setupThumbnailFlowPane();
      createThumbnailPanels();

      /****** ^^^^^^^^^^^^ ******/

    }
  });

  uploadingFileTask.setOnFailed(evt -> {
    uploadingFileTask.getException().printStackTrace(System.err);
    System.err.println(Arrays.toString(uploadingFileTask.getException().getSuppressed()));
  });

  Thread uploadingFileThread = new Thread(uploadingFileTask);
  uploadingFileThread.start();

}

文档上载后,将显示在一个选项卡中,该选项卡允许用户查看文档。

有一个二级选项卡,上载后禁用,直到完成另一个名为 createThumbnailPanelsTask ;

但是,在运行此任务之前, FlowPane 创建缩略图面板。这似乎没有问题,而且似乎不是GUI挂起的原因(这显然是 创建缩略图面板标记 ,但为了清楚起见,我将展示 setupThumbnailFlowPane() ):

设置缩略图流窗格()

public void setupThumbnailFlowPane() {
  stage = model.getStage();
  root = model.getRoot();

  secondaryTabScrollPane.setFitToWidth(true);
  secondaryTabScrollPane.setHbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);

  /**
  This will be removed from here when refactored but for now it is here,
  I don't think this is anything to do with my issue
  **/

  Set<Node> nodes = secondaryTabScrollPane.lookupAll(".scroll-bar");
  for (final Node node : nodes) {
    if (node instanceof ScrollBar) {
      ScrollBar sb = (ScrollBar) node;
      if (sb.getOrientation() == Orientation.VERTICAL) {
        sb.setUnitIncrement(30.0);
      }
      if (sb.getOrientation() == Orientation.HORIZONTAL) {
        sb.setVisible(false);
      }
    }
  }

  secondaryTab = new FlowPane();
  secondaryTab.setId("secondaryTab");
  secondaryTab.setBackground(new Background(new BackgroundFill(Color.LIGHTSLATEGRAY, new CornerRadii(0), new Insets(0))));
  secondaryTab.prefWidthProperty().bind(stage.widthProperty());
  secondaryTab.prefHeightProperty().bind(stage.heightProperty());
  secondaryTab.setPrefWrapLength(stage.widthProperty().intValue() - 150);
  secondaryTab.setHgap(5);
  secondaryTab.setVgap(30);
  secondaryTab.setBorder(new Border(new BorderStroke(Color.TRANSPARENT, BorderStrokeStyle.NONE, CornerRadii.EMPTY, new BorderWidths(8, 10, 20, 10))));
  secondaryTab.setAlignment(Pos.CENTER);
}

最后, createThumbnailPanels() 这就是我认为我遇到问题的地方。

假设发生的情况是,文档上载后,“上载文件”窗格隐藏,显示“查看器”选项卡和“辅助”选项卡。

此时将禁用辅助选项卡,并且还具有加载图像(A gif )在它的左边。

预期的行为是 创建缩略图面板() 任务将在后台运行,在完成之前,选项卡将保持禁用状态,但在此期间, GIF 图像将旋转,给人的印象是有一些负载发生。

加载完成后, GIF 将被删除,并启用选项卡,允许用户导航到该选项卡,并查看生成的缩略图面板。

但是,正如前面提到的,这一切都可以工作,任务是挂起GUI:

创建缩略图面板()

public void createThumbnailPanels() {
  Task<Void> createThumbnailPanelsTask = new Task<Void>() {
    @Override
    public Void call() {
      if (model.getIcePdfDoc() != null) {
        numberOfPagesInDocument = model.getIcePdfDoc().getNumberOfPages();
        for (int thumbIndex = 0; thumbIndex < numberOfPagesInDocument; thumbIndex++) {
          ThumbnailPanel tb = new ThumbnailPanel(thumbIndex, main, model);
          Thumbnail tn = new Thumbnail(tb);
          model.setThumbnailAt(tn, thumbIndex);
          eventHandlers.setMouseEventsForThumbnails(tb);

          /*
          I have added this in as I am under the impression that a task runs in a background thread,
          and then to update the GUI, I need to call this:
          */

          Platform.runLater(() -> {
            secondaryTab.getChildren().add(tb);
          });

        }

      }

      return null;
    }
  };

  createThumbnailPanelsTask.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
    @Override
    public void handle(WorkerStateEvent event) {

      /*
      Further GUI modification run in setOnSucceeded so it runs on main GUI thread(?)
      */
      secondaryTabScrollPane.setContent(secondaryTab);
      secondaryTab.setDisable(false);
      secondaryTab.setGraphic(null);

    }
  });

  createThumbnailPanelsTask.setOnFailed(evt -> {
    createThumbnailPanelsTask.getException().printStackTrace(System.err);
    System.err.println(Arrays.toString(createThumbnailPanelsTask.getException().getSuppressed()));
  });

  Thread createThumbnailPanelsThread = new Thread(createThumbnailPanelsTask);
  createThumbnailPanelsThread.start();
}

在创建面板时,禁止GUI挂起,一切都可以正常工作。

一旦创建了它们,就可以再次控制GUI,加载 GIF 已删除,选项卡已启用,用户可以导航到它并查看面板。

清楚地 ,这里的并发性缺少一些东西。

如前所述,我觉得任务是在后台线程中运行的,所以我有点困惑为什么它看起来不这样做。很明显,我错过了什么。

我已经阅读、阅读和阅读了并发性,但似乎无法找出我的方法中哪里出错了。我很想尝试使用一个服务,但是,我觉得考虑到这一点,我觉得事情过于复杂了,显然有一种简单的方法可以实现我想要实现的目标。

任何帮助都将不胜感激…向正确的方向推进,或者澄清我在理解上哪里出错了。

事先谢谢,毫无疑问,这是一件很明显的事情,一旦排序将帮助我避免这个问题在未来!

更新代码

创建缩略图面板()

 public void createThumbnailPanels() {
        Task<Void> createThumbnailPanelsTask = new Task<Void>() {
            //TODO: Need to check that it's a PDF
            @Override
            public Void call() {
                if (model.getIcePdfDoc() != null) {
                    numberOfPagesInDocument = model.getIcePdfDoc().getNumberOfPages();
                    for (int thumbIndex= 0; thumbIndex< numberOfPagesInDocument; thumbIndex++) {
                        ThumbnailPanel tb = new ThumbnailPanel(thumbIndex, main, model);
                        Thumbnail tn = new Thumbnail(tb);                        
                        eventHandlers.setMouseEventsForThumbnails(tb);       
                        model.setThumbnailAt(tn, thumbIndex);
                        model.setThumbnailPanels(tb);
                    }
                    setThumbnailPanelsToScrollPane();
                }
                return null;
            }
        };

        createThumbnailPanelsTask.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
            @Override
            public void handle(WorkerStateEvent event) {
//              setThumbnailPanelsToScrollPane();
            }
        });

        createThumbnailPanelsTask.setOnFailed(evt -> {

createThumbnailPanelsTask.getException().printStackTrace(System.err);
            System.err.println(Arrays.toString(createThumbnailPanelsTask.getException().getSuppressed()));
        });

        Thread createThumbnailPanelsThread = new Thread(createThumbnailPanelsTask);
        createThumbnailPanelsThread.start();
    }

将缩略图面板设置为滚动窗格()。

 public void setThumbnailPanelsToScrollPane() {
         Task<Void> setThumbnailPanelsToScrollPaneTask = new Task<Void>() {
            //TODO: Need to check that it's a PDF
            @Override
            public Void call() {
                 Platform.runLater(() -> {                     
                    secondaryTab.getChildren().addAll(model.getThumbnailPanels());
                    secondaryTabScrollPane.setContent(main.informationExtractionPanel);
                    secondaryTab.setDisable(false);
                    secondaryTab.setGraphic(null);
                  });   

                return null;
            }
        };


        setThumbnailPanelsToScrollPaneTask.setOnFailed(evt -> {
                setThumbnailPanelsToScrollPaneTask.getException().printStackTrace(System.err);
            System.err.println(Arrays.toString(setThumbnailPanelsToScrollPaneTask.getException().getSuppressed()));
        });

        Thread setThumbnailPanelsToScrollPaneThread = new Thread(setThumbnailPanelsToScrollPaneTask);
        setThumbnailPanelsToScrollPaneThread.start();
    }

如果我打电话 setThumbnailPanelsToScrollPane(); 在setonsucceed中,它似乎不起作用。