活动处理程序不会被删除

Question

我正在努力加快使用GWT活动和地点.我正在测试最初在这篇好博客文章中找到的一些源代码.

我发现在bind()期间添加的处理程序似乎永远不会删除.我对Activity javadoc的一点了解让我觉得它们应该在调用Activity的onStop()方法时自动删除.

在调用此方法之前,它已注册的所有事件处理程序都将被删除.

但每次单击一个按钮时,相应的处理程序称为n + 1次.

我错过了什么？如果有更多我可以提供的信息,请告诉我.

以下是代码中的相关代码段:

public class ContactsActivity extends AbstractActivity {

private List<ContactDetails> contactDetails;
private final ContactsServiceAsync rpcService;
private final EventBus eventBus;
private final IContactsViewDisplay display;
private PlaceController placeController;

public interface IContactsViewDisplay {
    HasClickHandlers getAddButton();
    HasClickHandlers getDeleteButton();
    HasClickHandlers getList();
    void setData(List<String> data);
    int getClickedRow(ClickEvent event);
    List<Integer> getSelectedRows();
    Widget asWidget();
}

public ContactsActivity(ClientFactory factory) {
    GWT.log("ContactActivity: constructor");

    this.rpcService = factory.getContactServiceRPC();
    this.eventBus = factory.getEventBus();
    this.display = factory.getContactsView();
    this.placeController = factory.getPlaceController();
}

@Override
public void start(AcceptsOneWidget container, EventBus eventBus) {
    GWT.log("ContactActivity: start()");

    bind();
    container.setWidget(display.asWidget());
    fetchContactDetails();

}

public void bind() {

    GWT.log("ContactActivity: bind()");

    display.getAddButton().addClickHandler(new ClickHandler() {
        public void onClick(ClickEvent event) {
            GWT.log("Add button clicked");
            ContactsActivity.this.placeController.goTo(new NewContactPlace(""));
        }
    });

    display.getDeleteButton().addClickHandler(new ClickHandler() {
        public void onClick(ClickEvent event) {
            GWT.log("ContactActivity: Delete button clicked");
            deleteSelectedContacts();
        }
    });

    display.getList().addClickHandler(new ClickHandler() {
        public void onClick(ClickEvent event) {
            GWT.log("ContactActivity: List clicked");
            int selectedRow = display.getClickedRow(event);

            if (selectedRow >= 0) {
                String id = contactDetails.get(selectedRow).getId();
                ContactsActivity.this.placeController.goTo(new EditContactPlace(id));
            }
        }
    });
}

Answer 1

通过注册的活动.在EventBus传递给AbstractActivity#start()将被及时注销onStop()被调用.bind()但是,在上述方法中注册的事件处理程序不是通过EventBus抽象基类注册的,也不是可见的.您需要自己取消注册:

public class ContactsActivity extends AbstractActivity {
  private List<HandlerRegistration> registrations = new ArrayList();

  private void bind() {
    registrations.add(display.getAddButton().
      addClickHandler(new ClickHandler() { ... }));
    registrations.add(display.getDeleteButton().
      addClickHandler(new ClickHandler() { ... }));
    registrations.add(display.getList().
      addClickHandler(new ClickHandler() { ... }));
  }

  @Override
  public void onStop() {
    for (HandlerRegistration registration : registrations) {
      registration.removeHandler();
    }

    registrations.clear();
  }
}