gwt-polymer-elements

Introduction

Polymer: is a JavaScript library for building web applications with Web Components.
Polymer-Elements: is a collection of widgets built in Polymer. The collection is divided in sections: Iron, Paper, Gold, Neon, Platinum, Vaadin, etc.
GWT-Polymer-Elements: is a Java wrapper enabling Polymer Elements to be used in GWT projects. Right now it includes wrappers for Paper, Iron and Vaadin collections, but more might be added in the future.

The library has been generated using the Vaadin gwt-api-generator, an utility able to inspect polymer webcomponents and emit GWT Java code.

Because Polymer differentiates between collections, gwt-polymer-elements classes are prefixed with the same prefixes (Iron, Paper, Vaadin), in order to easily refer to the original web component, and to easily find the documentation related with it.

Demo

Visit our show case to see how components look like, and to take a look to the example code using each component.

Javadocs

When we parse the original components code to generate the Java API, we copy all the existing JS documentation so as it's available in the javadoc. Note that sometimes descriptions would refer to JS, but we consider that it's better to maintain the info.

Using the GWT library

NOTICE : We make extensive use of JsInterop a new feature in GWT for easily interacting with JavaScript. It is experimental in GWT-2.7 and will be stable in GWT-2.8.0, but starting from gwt-polymer-elements-1.2.1.0.beta1, we don't support 2.7.0 anymore nor it's legacy JsInterop syntax. If you got Uncaught java.lang.ClassCastException errors in the JavaScript console when running your application, it does mean that you are not using GWT-2.8.0-SNAPSHOT

Add vaadin-gwt-polymer-elements to your CLASSPATH

The .jar file includes all the java code and web components of Polymer Iron and Paper collections, so as you don't have to deal with the process of downloading and deploying all js wrapped libraries and components.

Using maven

If your project uses maven add the dependency:

 <dependencies>
   <dependency>
     <groupId>com.vaadin.polymer</groupId>
     <artifactId>vaadin-gwt-polymer-elements</artifactId>
     <version>1.2.3.0</version>
     <scope>provided</scope>
   </dependency>
 </dependencies>

Manually

otherwise you can download the vaadin-gwt-polymer-elements-x.x.x.x.jar archive and put it in your gwt project classpath.

Update your module configuration

Add this line to your *.gwt.xml module file:

 <inherits name="com.vaadin.polymer.Elements"/>

### Add the Web Components Polyfill

Nowadays, only Chrome has full native support for Web Components, therefore, to make your project work in all browsers, you have to include Polymer Polyfill, very early in your .html host page. Since vaadin-gwt-polymer-elements already is bundled with the polyfill, so you only have to replace myapp fragments with your actual application name.
```
<head>
  <script src="myapp/bower_components/webcomponentsjs/webcomponents.js"></script>
  <script src="myapp/myapp.nocache.js"></script>
</head>
```

Consuming Web Components in GWT

Vaadin gwt-polymer-elements bundles classes to build your application using either Widgets or JsInterop Elements. The former is the classic approach, while the latter will become the new tendency.

But Right now, Elements is the most difficult way because GWT lacks of a complete Elemental-2.0 API relying on JsInterop, and because JsInterop has not been fully released yet. We provide a very basic set of elemental interfaces limited to those needed for our implementation, they will be replaced by Elemental-2.0 when it was available.

In summary, for classic and production GWT projects it would be easier to use the Widget since the API would not have important changes. Otherwise, if you want to get rid of the widget hierarchy we recomend to start using the Element API mixing it with some DOM manipulation library like gwtquery.

Using the classic Widget API in Java.

PaperButton button = new PaperButton();
button.setIcon("polymer");
button.setLabel("Polymer");
button.setRaised(true);

button.addClickHandler(new ClickHandler() {
  public void onClick(ClickEvent event) {
    // ...
  }
});

RootPanel.get().add(button);

Note: Widget constructors accept any HTML content as argument which is appended to the web component rendered DOM

Using the Element API in Java.

// Create a new instance of PaperButton
PaperButtonElement button = Polymer.create(PaperButtonElement.TAG);
// Set some properties
button.setIcon("polymer");
button.setLabel("Polymer");
button.setRaised(true);

// Add event listeners
button.addEventListener("click", new EventListener() {
    public void onBrowserEvent(Event event) {
    // ...
    }
});

// Append to the html document
RootPanel.get().getElement().appendChild(button);

Using Widgets or Elements in UiBinder

 <ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
  xmlns:g='urn:import:com.google.gwt.user.client.ui'
  xmlns:p='urn:import:com.vaadin.polymer.paper.widget'>

 <ui:style>
   .container paper-button.colored {
     background: #4285f4;
     color: #fff;
   }
 </ui:style>

 <g:HTMLPanel>
   <!-- As Widget -->
   <p:PaperButton toggles="true" raised="true" active="true" addStyleNames="{style.colored}">active</p:PaperButton>

   <!-- As Element -->
   <paper-button raised="" noink="">Click me</paper-button>
 </g:HTMLPanel>

Styling your application.

Polymer uses Shadow DOM styling rules for providing scoped styling of the element’s local DOM. It supports some extra syntax which is not understable by the GWT GSS parser.

Polymer takes care of its syntax parsing any <style> block you might have in your host page, but if you want to specify some styling rules in UiBinder, you have to add your style blocks to any panel.

<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
  xmlns:g='urn:import:com.google.gwt.user.client.ui'
  xmlns:p='urn:import:com.vaadin.polymer.paper.widget'>

<g:HTMLPanel>
<style is="custom-style">
   paper-toolbar paper-icon-button {
      --paper-icon-button-ink-color: var(--paper-indigo-500);
   }
</style>
<p:PaperToolbar>
   <p:PaperIconButton icon="menu"/>
   <span class="title">Toolbar</span>
</p:PaperToolbar>
</g:HTMLPanel>

For more information about polymer styling syntax visit their documentation

Notes

Importing Web Components

Before using any component, you have to import the appropriate files. But gwt-polymer-elements comes with some utilities so as you it would be done automatically.

Widgets : When you use a widget, the import happens automatically

    PaperButton button = new PapperButton();

Elements : Create new components through the Polymer helper class

    PaperButtonElement button = Polymer.create(PaperButtonElement.TAG);

Dynamic imports : Polymer has a couple of methods to do the import dynamically

    Polymer.importHref("paper-button/paper-button.html");

Static imports : Adding tags to the hosted page head is the traditional way to make webcomponents available if you want them in a mixed application (DOM, JS, or GWT) or if you want to be sure that web components are available from the beginning.

   <link rel='import' href='application_context/bower_components/paper-button/paper-button.html'></link>

Asynchronous issues

Polymer 1.0.x does not allow using custom properties before the web component has been initialized. Thus gwt-polymer-elements comes with some methods which helps to run callbacks when the component starts ready. If you use widgets, the library would be able to deal with properties set very early, but call to some methods could not work

  PaperButtonElement button = Polymer.createElement(PaperButtonElement.TAG);
  Polymer.ready(button, new Function() {
     public Object call(Object args) {
        // Set button properties here
     }
  })

  PolymerButton button = new PolymerButton();
  // You could set methods here
  button.set...

  button.ready(new Function() {
     public Object call(Object args) {
       // But you have to enclose in a callback calls to element methods
     }
  });


  Polymer.importHref(Arrays.asList("paper-tabs", "paper-tab-element"), new Function() {
     public Object call(Object args) {
        // Create your elements here and call their methods
     }
  })

Contributors

Building the project

To compile the vaadin-gwt-polymer-elements library by yourself.

Clone the repository with $ git checkout https://github.com/vaadin/gwt-polymer-elements.git
Change to the project folder $ cd gwt-polymer-elements
Run $ npm install to download all components to the src/main/resources folder, to create all java files needed for GWT in the src/main/java/ folder and to compile and install the components library in you local maven repo.

Running the demo locally

To run and debug the demo, go to the demo folder $ cd demo
Run $ mvn gwt:run to run the demo in SuperDevMode, otherwise run $ mvn clean package to build the demo application under target directory.
Host the demo either: by running for example $ serve target/gwt-polymer-demo (requires serve) or deploying the generated target/gwt-polymer-demo.war to your favourite servlet container.

pkdevboxy / gwt-polymer-elements Goto Github PK