Question

这是here的后续行动。

我正在实现一个表，它将数据异步加载到表格单元格中。问题是，表格单元格有时无法正确更新。有时候它会以某种方式“挂起”并且显示“正在加载......”永远。只有当我在表格中稍微滚动时，实际值才会更新。

要重现，请在表格中快速向下滚动应用程序。有些单元格不会显示“延迟加载”值，而是占位符字符串。

延迟加载属性如下所示：

public abstract class LazyLoadingStringProperty extends SimpleStringProperty {

public static final String DEFAULT_LOADING_STRING = "Loading..";
private static final ExecutorService exe = Executors.newCachedThreadPool();
private String loadingString = DEFAULT_LOADING_STRING;

private boolean loaded = false;

public LazyLoadingStringProperty() {

}

public boolean isLoaded() {
    return loaded;
}

public void setLoaded(final boolean loaded) {
    this.loaded = loaded;
}

public String getLoadingString() {
    return loadingString;
}

public void setLoadingString(final String loadingString) {
    this.loadingString = loadingString;
}

@Override
public String getValue() {
    if (!loaded) {
        Platform.runLater(() -> startLoadingService());
        return loadingString;
    }
    return super.getValue();
}

protected void startLoadingService() {

    final Service<String> s = new Service<String>() {

        @Override
        protected Task<String> createTask() {
            return LazyLoadingStringProperty.this.createTask();
        }
    };

    s.setExecutor(exe);

    s.setOnFailed(e -> {
        setLoaded(true);
        setValue(s.getException().getLocalizedMessage());

    });

    s.setOnSucceeded(e -> {
        setLoaded(true);
        setValue(s.getValue());

    });
    s.start();
    // System.err.println("Started");
}

protected abstract Task<String> createTask();

}

Applikation看起来像这样：

public class ExampleTable extends Application {

    private static final int NUM_ELEMENTS = 500;

    private final TableView<ExampleBean> table = new TableView<>();

    private final ObservableList<ExampleBean> data = FXCollections.observableArrayList();

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

    @Override
    public void start(final Stage stage) {
        final Scene scene = new Scene(new Group());
        stage.setTitle("Table View Sample");
        stage.setWidth(300);
        stage.setHeight(500);

        final TableColumn<ExampleBean, String> c1 = new TableColumn<>("A");
        c1.setCellValueFactory(new PropertyValueFactory<ExampleBean, String>("p1"));
        final TableColumn<ExampleBean, String> c2 = new TableColumn<>("B");
        c2.setCellValueFactory(new PropertyValueFactory<ExampleBean, String>("p2"));
        final TableColumn<ExampleBean, String> c3 = new TableColumn<>("C");
        c3.setCellValueFactory(new PropertyValueFactory<ExampleBean, String>("p3"));

        c1.setPrefWidth(100);
        c2.setPrefWidth(100);
        c3.setPrefWidth(100);


        for (int i = 0; i < NUM_ELEMENTS; i++) {
            data.add(new ExampleBean());
        }

        final ScrollPane sp = new ScrollPane();
        sp.setContent(table);
        sp.setMaxHeight(Double.POSITIVE_INFINITY);
        sp.setMaxWidth(Double.POSITIVE_INFINITY);
        sp.setFitToHeight(true);
        sp.setFitToWidth(true);

        table.setItems(data);
        // table.setMaxHeight(Double.POSITIVE_INFINITY);
        // table.setMaxWidth(Double.POSITIVE_INFINITY);
        table.getColumns().addAll(c1, c2, c3);

        final VBox vbox = new VBox();
        vbox.setSpacing(5);
        VBox.setVgrow(sp, Priority.ALWAYS);
        vbox.getChildren().addAll(sp);

        scene.setRoot(vbox);


        stage.setScene(scene);
        stage.show();
    }
}

可以找到完整的可运行代码here。

Answer 1

~~它看起来像是JavaFX服务中的一个错误...~~

由于没有保存对var options = RRule.parseString("FREQ=DAILY;INTERVAL=6"); options.dtstart = new Date(2018, 2, 1, 9, 30); options.until = new Date(2018, 3, 1, 9, 30); var rule = new RRule(options); rule.all(); // enumerate occurrences个实例的引用，因此它们被垃圾收集有时它们中的一些在任务完成之前就被垃圾收集了在这种情况下，不会调用服务的Service和onFailed属性的侦听器。

简单的解决方案是使用onSucceeded对象保存服务引用：

LazyLoadingStringProperty

但是没有必要并行加载一个包含许多任务的值。因此，每个值的一项服务绰绰有余：

...
private ArrayList<Service<String>> services = new ArrayList<>();

protected void startLoadingService() {

    final Service<String> s = new Service<String>() {
        @Override
        protected Task<String> createTask() {
            return LazyLoadingStringProperty.this.createTask();
        }
    };
    services.add(s);
    ...

延迟加载FXProperties

1 个答案: