java - 如何将 Java ChangeListener 添加到方法返回

Question

我有一个任务控制 GUI，带有一个“中止”按钮，可以调用一些取消代码(工作正常)。但是，我想将按钮的禁用状态与任务是否正在运行同步，以便在任务未运行时禁用该选项。我可以通过 Boolean Future.isDone() 方法检查任务的状态，但我希望 JavaFX 通过绑定(bind)属性自动管理状态。但我不知道如何建立绑定(bind)，或在方法上设置 ChangeListener。谁能建议如何最好地完成任务？

编辑:我认为这个问题最终可以归结为“如何包装 Future.isDone() 使其成为 Observable？”

非常感谢指导。

Answer 1

使用任务。您可以观察state属性来修改Button的disabled属性:

private ExecutorService service;

@Override
public void stop() throws Exception {
    service.shutdownNow();
}

@Override
public void init() throws Exception {
    service = Executors.newSingleThreadScheduledExecutor();
    // service = new ThreadPoolExecutor(1, 2, 1, TimeUnit.SECONDS, new ArrayBlockingQueue<>(10));
}

@Override
public void start(Stage primaryStage) {
    Button startButton = new Button("Start");

    Task<Void> task = new Task<Void>() {

        @Override
        protected Void call() throws Exception {
            Thread.sleep(5000);
            System.out.println("task finished");
            return null;
        }

    };

    Button cancelButton = new Button("cancel");
    cancelButton.setOnAction(evt -> task.cancel());
    cancelButton.setDisable(true); // button disabled before submitting task

    startButton.setOnAction((ActionEvent event) -> {
        startButton.setDisable(true);

        // cancel Button enabled until task is succeeded/failed/was cancelled
        cancelButton.disableProperty().bind(Bindings.createBooleanBinding(() -> {
            switch (task.getState()) {
                case CANCELLED:
                case FAILED:
                case SUCCEEDED:
                    return true;
                default:
                    return false;
            }
        }, task.stateProperty()));

        // simulate some work to be done by the service
        service.submit(() -> {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException ex) {
            }
            System.out.println("runnable finished");
        });
        service.submit(task);
    });

    // show state as text
    Text text = new Text();
    text.textProperty().bind(task.stateProperty().asString());

    VBox root = new VBox(10, startButton, cancelButton, text);

    Scene scene = new Scene(root, 300, 300);

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