vaadin聊天对话框中的输出hello（Spring Boot和Spring Scheduler + vaadin 14）

Question

我在vaadine和spring boot上创建了一个聊天记录。所以我对调度程序有问题，我想编写一个每秒显示“ hello”的调度程序，但是我该如何写，以便它每秒调用一次hello，只有这样输出示例-

hello 1 - (when 1 second has passed)
hello 2 - (after two seconds)
hello 3 - (after three seconds)
.
.
.
.
hello 45 - (after 45 seconds)
.
.
.
.
hello 100 - (after 100 seconds)

图像示例

我的代码，登录后如何在聊天中启动调度程序

public class MainView extends VerticalLayout {

    private final MessagesInfoManager messagesInfoManager;
    private final RestService restService;
    private String username;



     private int count=0;

    @Autowired
    public MainView(RestService restService) {
        this.messagesInfoManager = MessageConfigurator.getInstance().getChatMessagesInfoManager();
        addClassName("main-view");
        setSizeFull();
        setDefaultHorizontalComponentAlignment(Alignment.CENTER);

        H1 header = new H1("Vaadin Chat");
        header.getElement().getThemeList().add("dark");

        add(header);

        askUsername();
        this.restService = restService;
    }

    private void askUsername() {
        HorizontalLayout layout = new HorizontalLayout();
        TextField usernameField = new TextField();
        Button startButton = new Button("Start chat");

        layout.add(usernameField, startButton);

        startButton.addClickListener(click -> {
            username = usernameField.getValue();
            remove(layout);
            showChat(username);
        });

        add(layout);
    }

    private void showChat(String username) {
        MessageList messageList = new MessageList();

        List<Message> lasts = restService.getLast();
        for (Message message : lasts) {
            messageList.add(new Paragraph(message.getFrom() + ": " + message.getMessage()));
        }

        add(messageList, createInputLayout(username, messageList));
        expand(messageList);
    }

    private Component createInputLayout(String username, MessageList messageList) {
        HorizontalLayout layout = new HorizontalLayout();
        layout.setWidth("100%");

        TextField messageField = new TextField();
        messageField.addKeyDownListener(Key.ENTER, keyDownEvent -> sender(messageField, messageList));
        Button sendButton = new Button("Send");
        sendButton.addThemeVariants(ButtonVariant.LUMO_PRIMARY);

        layout.add(messageField, sendButton);
        layout.expand(messageField);

        messageField.addFocusListener(event -> {
            for (Message message : messagesInfoManager.getMessagesByUI(getUI())) {
                if (!message.getFrom().equals(username)) {
                    message.setUnread(false);
                    this.restService.updateMessage(message.getId(), message);
                }
            }
        });

        sendButton.addClickListener(click -> sender(messageField, messageList));
        messageField.focus();

        return layout;
    }

    private void sender(TextField textField, MessageList messageList) {
        Message message = new Message(username, textField.getValue());
        message = restService.saveMessage(message);
        messagesInfoManager.updateMessageUIInfo(new MessageInfo(messageList, message, this));
        textField.clear();
        textField.focus();
    }






@Scheduled (fixedDelay = 1000)
public void test() {
    count++; 
    System.out.println("Hello"+count);

}
}

在编译器显示中，现在我需要聊天

Answer 1

您如何用Java建立调度程序与Vaadin本身并没有多大关系。您可以使用您运行的第二个线程，或者似乎已经使用的现成工具。如果我没记错的话，它看起来像一个Spring功能。

之后，您将更新Vaadin组件以包含新消息。例如，您可以将messageList设置为一个字段，然后在test()中为其添加一个新段落。或使用您必须从那里推送消息的后端服务。

当您确实从辅助线程更新UI时，请记住，您可能会遇到争用条件。因此，您应该lock the user session for the time that you make UI changes。