If you investigate your example from the last chapter you will see the following project structure. An GWT application consists of the following parts Module descriptor: XML file which specifies mainly the entry point of the application. It has the name of your module plus. Additional public resources, e. Source code: under your default package you find a package "client".
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Besides being a more natural and concise way to build your UI than doing it through code, UiBinder can also make your app more efficient.
UiBinder naturally takes advantage of this, and the result is that the most pleasant way to build your app is also the best way to build it. But as you learn what UiBinder is, you should also understand what it is not. It is not a renderer, or at any rate that is not its focus. There are no loops, no conditionals, no if statements in its markup, and only a very limited expression language.
UiBinder allows you to lay out your user interface. The rest of this page explains how to use UiBinder through a series of typical use cases. Internationalization - UiBinder explains how to internationalize it. Quick start: If instead you want to jump right in to the code, take a peek at this patch.
It includes the work to change the venerable Mail sample to use UiBinder. Look for pairs of files like Mail. Any object declared in the ui. In the Java code, a field with the same name is marked with the UiField annotation. When uiBinder. Our HelloWorld object is nothing special, it has no superclass. But it could just as easily extend UIObject. Or Widget. Or Composite. There are no restrictions.
However, do note that the fields marked with UiField have default visibility. If they are to be filled by a binder, they cannot be private. The HelloWorldWidget can be added to any panel class. In order to use a set of widgets in a ui. This says that every class in the com. Using Panels Any panel in theory, anything that implements the HasWidgets interface can be used in a template file, and can have other panels inside of it.
Unlike almost everything else that appears in the template, they do not represent runtime objects. When you need such characters, you have to define them yourself. However, your IDE may fetch it. How many times have you written something like this? Using a widget that requires constructor args Every widget that is declared in a template is created by a call to GWT.
In most cases this means that they must be default instantiable; that is, they must provide a zero-argument constructor. However, there are a few ways to get around that. Suppose you have an existing widget that needs constructor arguments: public CricketScores String CricketScores has no default zero args constructor.
This means that the compiler will warn you if you misspell the class name when you try to use it e. Most real world projects will probably keep their CSS in a separate file. In the example given below, the src values are relative to the location of the ui.
Use the styleName attribute to override whatever CSS styling the widget defaults to just like calling setStyleName in code. Programmatic access to inline Styles Your code will need access to at least some of the styles your template uses. That means that it needs to implement that interface defined in the Java source for the MyFoo widget above and provide the two CSS classes it calls for, enabled and disabled.
The setEnabled method uses that field to apply the enabled and disabled styles as the widget is turned on and off. Using an external resource Sometimes your template will need to work with styles or other objects that come from outside of your template. In this case it will be instantiated via a call to GWT. Read on to see how pass an instance in instead of having it created for you. Note that there is no requirement that a ui:with resource implement the ClientBundle interface; this is just an example.
Any setters or constructor arguments can be called on the resource object this way, just as for any other object in the template. In the example below, note how the FancyResources object accepts a reference to the Resource declared in the previous example. If instead you want your code to be in charge of finding or creating that resource, you have two means to take control. If your factory method needs arguments, those will be required as attributes.
Hello Html Resources Relying only on text as we did in the previous example is pretty limiting. Any SafeHtml class can be used directly, much the same as a widget. Objects used this way are kind of a one-way-ticket.
Their SafeHtml. You have a nice view interface, and a templated widget that implements it. How might you use several different XML templates for the same view?
Fair warning: This is only meant to be a demonstration of using different ui. It is not a proven pattern for implementing themes in an application, and may or may not be the best way to do that. You want to take advantage of LazyPanel. Elsewhere in the app is a template with a lot of dom element fields.
You know that when your ui is built, a getElementById call is made for each and every one of them. In a large page, that can add up. These templates can only contain HTML elements, no widgets or panels. Now, define a HelloWorldCell widget. Add an interface that extends the UiRenderer interface instead of UiBinder.
Use as many as needed to render your data. Cell event handling with UiBinder Cell events require you to write the code to determine the exact cell on which the event was received, and even more. UiBinder handles a lot of this work for you. It will route events to your handler methods based on the event type, and the HTML element on which the event was received. Taking the HelloWorldCell. This allows the generated code to distinguish the span element from the other elements in the template.
The onBrowserEvent in the renderer interface only requires the first three arguments to be defined. Any other arguments after that are for your convenience, and will be passed verbatim to the handlers.
The type of the first parameter, ClickEvent , will determine the type of event handled. This is useful when you need to manipulate the DOM elements. That is, for a ui:field named someName, the getter should be getSomeName Element parent. Just define a getter with no parameters matching the style name and returning the style type.
Notice that you need to get the style name using the red accessor method. The GWT compiler obfuscates the actual name of the style to prevent collisions with other similarly named styles in your application.
Besides being a more natural and concise way to build your UI than doing it through code, UiBinder can also make your app more efficient. UiBinder naturally takes advantage of this, and the result is that the most pleasant way to build your app is also the best way to build it. But as you learn what UiBinder is, you should also understand what it is not. It is not a renderer, or at any rate that is not its focus. There are no loops, no conditionals, no if statements in its markup, and only a very limited expression language.
GWT - FormPanel Widget
You might be a Java developer who would like to be able to apply the software engineering principles of object-oriented programming and leverage the tools in your Java IDE when writing applications for the web. These tutorials are based on the development of two example applications, such that the user learns different GWT concepts in each step. StockWatcher is an application for monitoring stock variations, and you can get the sources from github TodoList a web application to create and maintain a Todo checklist in browser. Sources are available at github as well. In these tutorials, we use Eclipse because it is open source. However, GWT does not tie you to Eclipse.