Vaadin - 在视图之间传递数据

Question

我在Vaadin和JavaEE中都很新,我认为我有基本的问题,但很乐意提供帮助.

我的Vaadin项目中有3个类,它们是:主类,只响应启动和创建导航器:

public class MyprojectUI extends UI {


    public Navigator navigator;
        public static final String SECOND_VIEW = "SecondView";

        @WebServlet(value = "/*", asyncSupported = true)
        @VaadinServletConfiguration(productionMode = false, ui = MyprojectUI.class)
        public static class Servlet extends VaadinServlet {
        }

        @Override
        protected void init(VaadinRequest request) {
            final VerticalLayout layout = new VerticalLayout();
            layout.setMargin(true);
            setContent(layout);

            ComponentContainerViewDisplay viewDisplay = new ComponentContainerViewDisplay(layout);
            navigator = new Navigator(UI.getCurrent(), viewDisplay);
            navigator.addView("", new FirstView());
            navigator.addView(SECOND_VIEW, new SecondView());
        }

    }

和两个观点类:

public class FirstView extends HorizontalLayout implements View {

    TextArea text = new TextArea();
    Button button = new Button("go");

    @Override
    public void enter(ViewChangeEvent event) {
        this.addComponent(text);
        this.addComponent(button);
        button.addClickListener(new ClickListener() {
            @Override
            public void buttonClick(ClickEvent event) {
                getUI().getNavigator().navigateTo(MyprojectUI.SECOND_VIEW);
            }
        });
    }
}

-

public class SecondView extends HorizontalLayout implements View {

    Label label = new Label("Passed text here");

    @Override
    public void enter(ViewChangeEvent event) {
        this.addComponent(label);
    }

}

如何将TextArea中的数据传递到第二个视图？我希望在单击"go"按钮时将标签文本设置为TextArea中的文本.

感谢帮助.

Answer 1

我建议您应用Model-View-Presenter模式.查看已经完成.这里不需要模型.只需写一个演示者.在MVP中,Presenter由视图触发,然后演示者从视图中收集所需的数据,进行一些计算和更新视图.在目前的情况下,它可能看起来像:

class Presenter {
  FirstView firstView;
  SecondView secondView;
  public Presenter (FirstView firstView, SecondView secondView) {
    this.firstView = firstView;
    this.secondView = secondView;
  }
  public void goClicked(UI ui) {
     secondView.label.setValue(firstView.text.getValue());
     ui.getNavigator().navigateTo(MyprojectUI.SECOND_VIEW);
  }
}

代码简化了,推荐的做法是定义一个视图接口而不是直接字段访问,但主要思路是一样的.