GWT: How to create a new page

I have a GWT MVP application 开发者_如何学Pythonwith one page. How can I create a new page and link to it?

you can do one thing, at same page make different layouts and at particular action you can hide one layout and show other layout or component.

GWT has support for pages within application via URL fragment identifier, i.e. http://www.yourhost.vom/main#pagename, where "pagename" is a fragment identifier representing a "page" within your app.

1. Enable history support by adding an iframe to your host page:

   <iframe src="javascript:''" 
           id="__gwt_historyFrame" 
           style="width:0;height:0;border:0">
   </iframe>
   

2. Register a ValueChangeHandler to be notified when history (page) changes. Within this handler you put a logic that displays the new page.

3. Go to a particular page by calling History.newItem("newpage")

I created a open source, MIT licensed project to ease the page navigation handling in GWT. Take a look at the GWT Views project.

Using it you can define a View (a Widget referenced by an unique URL token) using simple Java annotations. The framework takes care of code-splitting for you, and hides all the boilerplate code.

Here is an example:

@View(Login.TOKEN)
public class Login extends Composite {
//... your code, you can use UIBinder, procedural UI, whatever you like

When using History.newItem(Login.TOKEN) the Login widget will be rendered at the page.

There are a lot of common use cases handled by the framework as well, such as ViewContainers, 404 pages, Google Analytics tracking, and user authorization.

This is what I ended up doing:

package com.example.client;

import java.util.logging.Logger;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.shared.GWT;
import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.user.client.History;
import com.google.gwt.user.client.ui.RootPanel;

public class Controller implements EntryPoint {
    private static Controller instance;
    private static final Logger log = Logger.getLogger(Controller.class.getName());

    // I have a feeling GWT does not respect private constructors, or else it uses some other voodoo.
    private Controller(){}

    public static Controller getInstance() {
        if (instance == null) instance = new Controller();
        return instance;
    }

    @Override
    public void onModuleLoad() {
        String token = History.getToken();
        log.info("****************************** token:"+token);
        History.addValueChangeHandler(new ValueChangeHandler<String>() {
            @Override
            public void onValueChange(ValueChangeEvent<String> event) {
                navigate(event.getValue());
            } // onValueChange
        });
        if (token == null || token.length() == 0) History.newItem(Login.TOKEN); // no token
        else navigate(token); // restore app state
    }

    private static void navigate(String token) {
        RootPanel rootPanel = RootPanel.get("gwtApp");
        if (rootPanel.getWidgetCount() > 0) rootPanel.remove(0); // clear the page

        if (Login.TOKEN.equals(token)) {
            Login page = Login.getInstance();
            page.onModuleLoad();
        } else if (MainApp.TOKEN.equals(token)) {
            MainApp page = MainApp.getInstance();
            page.onModuleLoad(); // display the page
//          page.setAuthenticated(true);
//          page.setUsername(email);
        }

    }

} // Controller

In your *.gwt.xml file:

<entry-point class='com.example.client.Controller' /> 

Now when you want to go to a new page:

History.newItem(Login.TOKEN);